Sciencemadness Discussion Board

Strategies in Designing Ideal Explosives

AndersHoveland - 16-7-2011 at 15:48

When designing explosive molecules there are several strategies that are used to maximize explosive performance and physical stability. This topic is for discussion about such strategies.

Incorporating Nitrogen
Nearly all explosives of any functional importance incorporate nitrogen into their molecular structures. Nitrogen atoms primarily serve as a way to hold oxygen atoms to the molecule, so that the formation of carbon-oxygen or hydrogen-oxygen bonds will release more energy than the oxygen-nitrogen bonds that need to be broken. The incorporation of nitrogen into a molecule can also compensate for lack of usable oxygen, as the formation of diatomic nitrogen (N2) releases energy. Generally, explosives which contain more bonds between nitrogen atoms are much more powerful than those that contain fewer bonds between nitrogen atoms. This may seem somewhat paradoxical because it is a common conception that nitrogen-nitrogen bonds are very strong. More nitrogen-nitrogen bonds mean fewer other atoms are bonded to nitrogen. A single carbon-nitrogen bond is nearly twice as strong as a single bond between two nitrogen atoms, while a carbon-nitrogen double bond is nearly 50% stronger than a similar nitrogen-nitrogen double bond. It is only the triple bond between two nitrogen atoms that is stronger (only slightly) than a carbon-nitrogen triple bond.

Nitrogen-Hydrogen bonds
Amino groups can often act as electron donating groups, making explosives less sensitive. The hydrogen bonding in amino groups also greatly increases intermolecular attraction, leading to higher densities.

Density
Just because a molecule is bigger and has more nitro groups does not necessarily mean it will be more powerful than a smaller molecule with fewer nitro groups. Smaller molecules can often pack together to result in higher densities than larger molecules. For example, DADNE, which has the formula C2N4H4O4, has a higher density and thus detonation velocity than RDX, C3H6N6O6. Caged molecules, such as TEX and HNIW, also tend to have higher densities.

Molecular Strain
Another strategy that has been employed is designing molecules with strained bonds. Octonitrocubane is an extreme example of this. Strained bonds require less energy to break. There has been some experimentation with triangular rings, but such compounds are generally much less stable. Cyclic square rings are ideal. Pentagonal rings also have a lesser degree of strained bonds. Hexagonal rings, however, do not contain strained bonds, and are in fact very stable.

The best potential molecules combine several different strategies listed above together. When designing molecules, it is best not to take any of the above strategies to an extreme, but rather to incorporate elements from most of the strategies, to have a “well-rounded” design.


[Edited on 16-7-2011 by AndersHoveland]

Fusionfire - 17-7-2011 at 04:02

Oooh, many other comments, my friend :D
1) In general, references/citations for your statements would be helpful for us non-chemists here ;)

2) Oxygen balance.
http://en.wikipedia.org/wiki/Oxygen_balance
TNT has an OB of -74% while AN has an OB of +20%

An OB deficit means that the explosive's potential is not being used to the fullest, IOW fuel is being wasted. An ideal explosive from an energetics point-of-view would be one where either the molecule has an OB of zero, or it is mixed into a composite such that the OB is zero.

3)
Quote:
Nitrogen-Hydrogen bonds
Amino groups can often act as electron donating groups, making explosives less sensitive. The hydrogen bonding in amino groups also greatly increases intermolecular attraction, leading to higher densities.


Not quite sure how electron donating groups de-sensitise explosives. Please elucidate.

4) Mean reactant diffusion distance. In solid molecular explosives, the diffusion distances are of molecular lengths. In thermites, it is of the order of particle sizes. This has a direct implication on the reaction rate of the explosive.

5) Activation energy. Thermites have a high activation energy (both to overcome the passivation layer and to free the oxygen from the less electropositive cation), hence their reaction kinetics are not ideal for use as explosives.

6) Enthalpy of the reaction. Higher heats evolved -> higher pressures evolved.

7) Moles of gas evolved per moles of reactant. More gas -> more destructive explosive.
Quote: Originally posted by AndersHoveland  
When designing explosive molecules there are several strategies that are used to maximize explosive performance and physical stability. This topic is for discussion about such strategies.

Incorporating Nitrogen
Nearly all explosives of any functional importance incorporate nitrogen into their molecular structures. Nitrogen atoms primarily serve as a way to hold oxygen atoms to the molecule, so that the formation of carbon-oxygen or hydrogen-oxygen bonds will release more energy than the oxygen-nitrogen bonds that need to be broken. The incorporation of nitrogen into a molecule can also compensate for lack of usable oxygen, as the formation of diatomic nitrogen (N2) releases energy. Generally, explosives which contain more bonds between nitrogen atoms are much more powerful than those that contain fewer bonds between nitrogen atoms. This may seem somewhat paradoxical because it is a common conception that nitrogen-nitrogen bonds are very strong. More nitrogen-nitrogen bonds mean fewer other atoms are bonded to nitrogen. A single carbon-nitrogen bond is nearly twice as strong as a single bond between two nitrogen atoms, while a carbon-nitrogen double bond is nearly 50% stronger than a similar nitrogen-nitrogen double bond. It is only the triple bond between two nitrogen atoms that is stronger (only slightly) than a carbon-nitrogen triple bond.

Nitrogen-Hydrogen bonds
Amino groups can often act as electron donating groups, making explosives less sensitive. The hydrogen bonding in amino groups also greatly increases intermolecular attraction, leading to higher densities.

Density
Just because a molecule is bigger and has more nitro groups does not necessarily mean it will be more powerful than a smaller molecule with fewer nitro groups. Smaller molecules can often pack together to result in higher densities than larger molecules. For example, DADNE, which has the formula C2N4H4O4, has a higher density and thus detonation velocity than RDX, C3H6N6O6. Caged molecules, such as TEX and HNIW, also tend to have higher densities.

Molecular Strain
Another strategy that has been employed is designing molecules with strained bonds. Octonitrocubane is an extreme example of this. Strained bonds require less energy to break. There has been some experimentation with triangular rings, but such compounds are generally much less stable. Cyclic square rings are ideal. Pentagonal rings also have a lesser degree of strained bonds. Hexagonal rings, however, do not contain strained bonds, and are in fact very stable.

The best potential molecules combine several different strategies listed above together. When designing molecules, it is best not to take any of the above strategies to an extreme, but rather to incorporate elements from most of the strategies, to have a “well-rounded” design.


[Edited on 16-7-2011 by AndersHoveland]

The WiZard is In - 17-7-2011 at 08:06

Quote: Originally posted by Fusionfire  
Oooh, many other comments, my friend :D
1) In general, references/citations for your statements would be helpful for us non-chemists here ;)

2) Oxygen balance.
http://en.wikipedia.org/wiki/Oxygen_balance
TNT has an OB of -74% while AN has an OB of +20%

An OB deficit means that the explosive's potential is not being used to the fullest, IOW fuel is being wasted. An ideal explosive from an energetics point-of-view would be one where either the molecule has an OB of zero, or it is mixed into a composite such that the OB is zero.


Sigh. Tooooo many here are in love with numbers, and go
into sissy fits over detonation velocity & oxygen balance.
Both numbers have limited/specific practical meaning.

This from PATR-2700 (A free DL.)


Oxygen-balance-57.jpg - 366kB Oxygen-balance-58.jpg - 298kB Oxygen-balance-59.jpg - 329kB Oxygen-balance-60.jpg - 129kB Oxygen-balance-61.jpg - 203kB Oxygen-balance-62.jpg - 387kB

No doubt the most misused term here do be
Explosive power a term which has a very
specific meaning.



djh
----
The WiZard is In - Is a
fan of none-dimensional
numbers. La deciBell - dB
(named after AG Bell's
daughter Deci.) is a
top of the list

Fusionfire - 17-7-2011 at 10:11

Quote: Originally posted by The WiZard is In  

Sigh. Tooooo many here are in love with numbers, and go
into sissy fits over detonation velocity & oxygen balance.
Both numbers have limited/specific practical meaning.


Thank ye kindly for the reference, Wizard :D. I read all of that. My comments are:

1) It can not be denied that fuel is being wasted when the OB of an explosive is substantially negative. The question is how to exploit this situation without adversely affecting the explosive properties.

ETN (+5.3% OB) can probably be mixed with PETN (-10%) quite well without affecting the VoD of either.

I am not sure if AN (+20%) or NaNO3 (+47%) in a composite with TNT (-74%) to have an OB of zero would actually reduce the VoD or simply produce more energy during afterburning and not detonation.

Therefore I agree with your reference when he says "OB correlates reasonably well with relative power, provided these comparisons are made for similar expls."

BTW is there an error in Table 1 for TNT? It lists the OB there as -21.6% but just to the left the calculation showed it to be -74%

2) Figure 1 shows pretty good correlation between OB and explosive power.

As an engineer I understood the theoretical meaning of explosive power to mean the reaction heats divided by the reaction time. The reaction heat can be calculated while I would estimate the reaction time to be the time taken for the VoD to traverse the sample of explosives, after making corrections for DDT/SDT.

3) I'm not quite sure I agree with you that VoD has limited practical meaning. High VoD leads to faster hollow charge jets/EFPs, more brisance and higher peak pressures. Hollow charges are the bread and butter of modern anti-armour weapons.

The WiZard is In - 17-7-2011 at 10:58

Quote: Originally posted by Fusionfire  

3) I'm not quite sure I agree with you that VoD has limited practical meaning. High VoD leads to faster hollow charge jets/EFPs, more brisance and higher peak pressures. Hollow charges are the bread and butter of modern anti-armour weapons.



Well ... I agree with myself! Given that US usage of explosives
and blasting agents is ca. 4 000 million pounds a year...
the small anount used in shaped charges meet the requirements of
"limited practical use." n'est-ce pas?

The most important factor for most is $$$$.

Explosives are tools - the one that does the best job for
the least price is the winner. Strange thing do however,
happen. Really expensive det cord is used to load holes to
blast rock! Lots and lots of small holes.

PLX is only used where its unique characteristic is useful,
the first (only) explosive used on the moon was carefully chosen,
like-wise the explosives used in lens for nuke warheads,
&c., &c....

Reminds me DuPont stopped making dynamite years ago,
it was tooo expensive to compete with ammonium nitrate
and aluminium slurry explosives.

Fusionfire - 17-7-2011 at 11:23

Quote: Originally posted by The WiZard is In  
Quote: Originally posted by Fusionfire  

3) I'm not quite sure I agree with you that VoD has limited practical meaning. High VoD leads to faster hollow charge jets/EFPs, more brisance and higher peak pressures. Hollow charges are the bread and butter of modern anti-armour weapons.



Well ... I agree with myself! Given that US usage of explosives
and blasting agents is ca. 4 000 million pounds a year...
the small anount used in shaped charges meet the requirements of
"limited practical use." n'est-ce pas?

The most important factor for most is $$$$.

Explosives are tools - the one that does the best job for
the least price is the winner. Strange thing do however,
happen. Really expensive det cord is used to load holes to
blast rock! Lots and lots of small holes.

PLX is only used where its unique characteristic is useful,
the first (only) explosive used on the moon was carefully chosen,
like-wise the explosives used in lens for nuke warheads,
&c., &c....

Reminds me DuPont stopped making dynamite years ago,
it was tooo expensive to compete with ammonium nitrate
and aluminium slurry explosives.


Well, bringing out the AN rabbit from the hat for quarrying is kind of cheating ;). When designer explosives were mentioned in the OP I thought "high performance regardless of cost" (otherwise octanitrocubane, et al wouldn't have been mentioned)

AN is produced in mass quantities for both agricultural and mining industries. It is also really insensitive, meaning that production is less complicated than more orthodox secondaries. This means it is safe to make and safe to (ab)use.

Chemically it is very simple too, and I'd hazard a guess as a non-chemical engineer that there is a strong correlation between complexity of the organic molecule (say measured by a combination of functional groups + MW) and cost to produce.

And of course civilian markets tend to be much larger than military ones.

The WiZard is In - 17-7-2011 at 11:54

Quote: Originally posted by Fusionfire  

And of course civilian markets tend to be much larger than military ones.


But not trivial.

Pueblo Army Depot

High Explosives Assorted 400 000 000 pounds.

Report of Ulta-Hazardous Substances at Federal Installations
in Colorado
EPA 18 April 1972
PB-255253

Years back I was on the mailing list (snail-mail) for US Gov
surplus explosives. You would be amazed at the tonnage of
scrap C4 there was offered for sale. Yahooo! Never go around
to finding out who purchased it.

Take good notes there will be ....

The WiZard is In - 17-7-2011 at 12:06

a test. But first let me get atop my High horse.

Brisance like Sabot, Fresnel (lens), Mine ball
are French words they are not pronounced the way
a speaker of English would pronounce them if they were
English words. Don't look like a amateur look up its (their)
pronunciation.

Extra credit try isochronous and Oaxaca.



Explosives-Brisance-Molecular-Structure-181.jpg - 494kB Explosives-Brisance-Molecular-Structure-182.jpg - 478kB Explosives-Brisance-Molecular-Structure-183.jpg - 525kB Explosives-Brisance-Molecular-Structure-184.jpg - 482kB Explosives-Brisance-Molecular-Structure-185.jpg - 507kB Explosives-Brisance-Molecular-Structure-186.jpg - 520kB

Fusionfire - 17-7-2011 at 12:32

Quote: Originally posted by The WiZard is In  
a test. But first let me get atop my High horse.

Brisance like Sabot, Fresnel (lens), Mine ball
are French words they are not pronounced the way
a speaker of English would pronounce them if they were
English words. Don't look like a amateur look up its (their)
pronunciation.

Extra credit try isochronous and Oaxaca.


Oooooh you are too kind, thank you again for another reference :D

Delightful reading material. Will respond tomorrow once I have had a chance to read & digest it.

BTW what reference management system do you use? What is the going rate of a mirror of your entire reference collection? :o :)

The WiZard is In - 17-7-2011 at 12:47

Quote: Originally posted by Fusionfire  


BTW what reference management system do you use? What is the going rate of a mirror of your entire reference collection? :o :)


Ref management system... mostly between my ears
backed up by searching my HD and Google/Deja for the stuff
I posted in the past without saving to my HD.Also eye-balling
my book shelves a plenty.

Mirror of your entire reference system?! A Vulcan Mind Meld perhaps.

AndersHoveland - 17-7-2011 at 12:57

Of course oxygen balance is important, but the concept can be very misleading. While all the hydrogens should ideally be oxidized to H2O, it is much less important to oxidize the carbons all the way to CO2. Formation of carbon monoxide is sufficient. As can be seen below, the inclusion of six atoms can lead to 2 molecules of carbon dioxide, or alternatively to 3 molecules of carbon monoxide, which will occupy a greater volume after decomposition.
(2)C + (4)O --> (2)CO2
(3)C + (3)O --> (3)CO
Despite this, explosives which result in CO2 as the decomposition product still tend to be slightly more powerful, but it also requires that more usable oxygen be incorporated into the molecule, and this typically leads to greater sensitivity as more nitro/nitramine groups are required. The trade-off is generally not worth it.

And there do exist several powerful tetrazole explosives that do not even contain oxygen. The carbon in these molecules does not really need to be "burned off" because the formation of HCN as decomposition product releases nearly as much energy as formation of N2.

While C--H bonds can potentially generate much more energy on being oxidized than N--H bonds, they also require more oxygen. If the molecule is oxygen-deficient it may be more practical to substitute out some of the carbon with nitrogen atoms instead.


Geminal Nitro Groups

Putting two nitro groups on the same carbon atom is another strategy that has been employed to improve oxygen balance. Although such compounds still tend not to be very sensitive to initiation, there exists the problem of thermal stability, where there is slow decomposition in storage under warm conditions, or rapid degredation if the explosive becomes subjected to the heat from flames outside the metal casing.

Geminal-dinitro refers to two nitro groups on the same carbon atom. Gem-dinitro groups show good potential for incorporation into the structures of new explosive molecules and propellants. Molecules containing either mono- or di-nitro alkanes are generally much less sensitive than nitrate esters, while still being quite energetic when detonated.

There are two primary reasons that nitro groups are not often incorporated into typical explosive molecules. The first is that, in many cases, it is much more complicated to introduce more than one nitro group onto the same molecule. While aromatic rings are easily nitrated into corresponding di- and tri-nitro compounds, most other molecules are much more difficult to nitrate to nitro compounds. Substitution reactions, in which a bromoalkane reacts with nitrite ions, give satisfactory yields for single substitution, but the yields greatly decrease for di- and tri- nitro substitution. The most energetic mono-nitro alkane is nitromethane, which has a significantly lower density relative to other common explosives. Simple nitrations with mixed acids generally fail to produce nitro alkanes. This is because of the Meyer reaction, in which (R)2CH(NO2) groups disproportionate under acidic conditions, oxidizing the carbon to leave either a ketone or carboxyl group. Molecules in which the carbon bonded to the nitro group is also bonded to three other carbon atoms are not vulnerable to this type of disproportionation. An example of such a molecule would be (CH3)3C(NO2).

The second reason is that most, but certainly not all, molecules which contain the gem-dinitro group are not thermally stable, despite usually being fairly insensitive to impact.

The examples of stable gem-nitro molecules seem to have one thing in common. In all cases, elimination of HNO2 and resultant formation of an unsaturated C=C bond, is not possible. In other words, the molecules lack an (R)2CHC(NO2)2CH(R)2 segment, or if such a segment does exist, the carbon-carbon bonds are under a high degree of strain.

Dinitropropanes that do not have a hydrogen atom on the same carbon as the dinitro group require a higher temperature for thermal decomposition than those that have such a hydrogen. P. S. DeCarli, D.S. Ross, Robert Shaw, E. L. Lee, H. D.Stromberg. For example, the solid compound 2,2-dinitro propane is thermally unstable when warmed. At 75degC, it partially decomposes, losing two thirds of its weight after two days. There are, however, several conditions under which gem-dinitro compounds can be thermally stable. In constrast, dinitromethane shows little thermal instability at room temperature, and the pure liquid shows no sign of decomposition after being stored for several months at 0degC. Dinitromethane is, however, significantly less thermally stable than mono-nitro alkanes.

Adding a fluorine atom to the gem-dinitro group, with a structure –CF(NO2)2, greatly lends stability to the gem-ditro group. An example of this is the energetic plasticizer bis(2-fluoro-2,2-dinitroethyl) formal (FEFO), which has excellent thermal stability. FEFO decomposes first at 150 ° C by rearrangement of the nitro group in the loss of nitric oxide and nitrite. Nitrogen dioxide is also formed at 170 ° C.

Other examples of gem-dinitro compounds without any thermal stability problems include 1,1-diamino-2,2-dinitroethylene (DADNE) and 1,3,3-trinitoazetidine (TNAZ). In the first case, the amino groups act as electron donors to the nitro groups through the carbon-carbon double bond. The molecule is effectively aromatic, which is indicated by the yellowish color of the pure compound. An extra electron is a gem-dinitro group, whether as an anion such as in the salt potassium dinitromethanate (K+ O2NCH=NO2- ), or present in an aromatic compound, greatly adds stability to the compound, both thermally and in terms of resistance to detonation. In the case of TNAZ, the high bond strain from the square ring configuration creates a high energy barrier for a hydrogen atom to ionize off and leave a double carbon-carbon bond as the extra electron reduces one of the nitro groups to a nitrite anion. In such instances, the -CH2—C(NO2)2— segment of the molecule, eliminate eliminates nitrous acid (HONO), leaving behind –CH=C(NO2)—. Formation of an unsaturated bond is much more difficult when there is a high degree of bond strain.



[Edited on 17-7-2011 by AndersHoveland]

Some times it the simple thing that counts...

The WiZard is In - 17-7-2011 at 12:58

through WW I the explosive of choice for bombs/shells was
picric acid. PA was rapidly replaced by TNT, not because TNT
had higher velocity of detonation, brisance, power, higher/lower
oxygen balance .... TNT was/is used simple because it has a
much lower melting point then PA.

Granted PA lived on in Explosive D, however, with the collapse
of Ship to Ship Gunnery, Dunnite has very little if any current use.


djh
----
Finally, there is the case of explosives
scientist who fabricated an ash tray from
cast TNT and kept it on his office desk
for the use of visitors, only revealing its
nature after they had extinguished a
cigarette in it with no untoward results.

H.J. Yellop
Explsion Investigation
The Forensic Science Society, 1980.



[Edited on 17-7-2011 by The WiZard is In]

AndersHoveland - 17-7-2011 at 13:14

Of course there are other properties of explosive compounds that must be considered, besides just explosive performance and sensitivity.

Melt-castability, thermal stability, toxicity, and chemical reactivity are important properties.
The energetic plasticizer FEFO, for example, is an ideal explosive except for two serious problems; it is extremely toxic, and it will slowly corrode virtually every type of container it could be placed in, including both glass and gold. It even seeps through and saturates teflon, leading to structural weakening of the polymer.
Trinitroanaline, despite initially being a very insensitive explosive, can spontaneously detonate during storage from a spontaneous run-away chemical degredation.
Picric Acid, while not too sensitive itself, can be dangerosuly sensitized by traces of metallic contaminants or by coming in cotact with brass/copper metal.
Hygroscopicity and stability in air are also considerations; TACN becomes difficult to detonate after being exposed to moist air, while acetone peroxide slowly sublimes away if left in an open container.

quote by Fusionfire: "Not quite sure how electron donating groups de-sensitise explosives."

Electron donating groups can introduce an extra electron into nitro groups, which greatly further stabilizes the nitro group.
The structure of DADNE is often shown as (NH2)2C=C(NO2)2,
but it would be more descriptive to show it as [+]NH2=C(NH2)--C(NO2)=NO2[-]. A similar structure could be shown for triamino,trinitro,benzene (TATNB) which is extremely insensitive. Consider that a perchlorate anion, ClO4[-], is much more stable than Cl2O7. The stability is a result of an extra electron.

Hydrogen bonding also, by increasing intermolecular attraction, makes explosive substances more difficult to ignite. (To state the obvious, note that hydrogen atoms bonded to carbon do not engage in "hydrogen bonding")
Electron donation also typically results in more polar molecules, meaning higher density.

[Edited on 17-7-2011 by AndersHoveland]

Fusionfire - 17-7-2011 at 13:37

Some parameters can be fiddled around with, with composite explosives. E.g. kieselguhr to desensitise NG hence dynamite, likewise plasticisers for RDX to improve formability hence PE4.

Toxicity and chemical reactivity are probably harder to deal with.

franklyn - 17-7-2011 at 13:42

Arrived late to this lively discussion
Just my 2 cents, Fusionfire pointedly observes that
" 1) It can not be denied that fuel is being wasted when the OB of an explosive is substantially negative."
this is equivalent to mixing a high grade explosive with inert binder.
Given that enthalpies of formation of the explosives in common use
all cluster around zero, it follows that whatever energy that can be
mustered must necessarily derive from autocombustion.
Exotic enhancements such as strain in caged formations and extreme
endothermicity for now remain relegated to experimental investigation.
Density is the one property which directly affects detonation pressure
and can be selected from available prospective candidate compounds.
Velocity is the best available rule of thumb in ranking explosives, most
closely gauging the performance exhibited by the various other testing
regimes.

.

AndersHoveland - 17-7-2011 at 14:00

I am just of the opinion that, while oxygen balance is certainly an important consideration, this particular property is being overemphasized by both professional researchers and by many in this forum. Ideal oxygen balance should not be pursued at the complete expense of neglecting all other strategies. This misconceptions likely stems from the fact that most all common explosives in use have relied almost exclusively on this single property. But to design better molecules for the future, the horizons will have to be expanded. It is much more difficult to synthesize molecules which incorporate the other strategies, however.

[Edited on 17-7-2011 by AndersHoveland]

Rosco Bodine - 17-7-2011 at 20:54

Quote: Originally posted by AndersHoveland  
Picric Acid, while not too sensitive itself, can be dangerosuly sensitized by traces of metallic contaminants or by coming in cotact with brass/copper metal.


Is that right? How big are the traces? Tell me/us all about it please. However, let us first be clear on the rules for substantiation ...no bullshit references or propaganda sources that are incorrect are acceptable. Only good confirmed reliable accurate information is allowed.

hissingnoise - 18-7-2011 at 02:05

Quote: Originally posted by The WiZard is In  
through WW I the explosive of choice for bombs/shells was
picric acid. PA was rapidly replaced by TNT, not because TNT
had higher velocity of detonation, brisance, power, higher/lower
oxygen balance .... TNT was/is used simple because it has a
much lower melting point then PA.

The main reason for the demise of PA in munitions was its relatively high sensitiveness.
In WWI, the British found that the German TNT-filled shells could penetrate a ship's armour, exploding within, causing great damage, whilst their PA-filled munitions exploded on contact and inflicted little damage . . .
A lesson learned?


franklyn - 18-7-2011 at 05:51

Quote: Originally posted by hissingnoise  

In WWI, the British found that the German TNT-filled shells could penetrate a ship's armour,
exploding within, causing great damage, whilst their PA-filled munitions exploded on contact
and inflicted little damage . . .


That's very deceptive or else you draw the wrong conclusion.
The only self initiated munitions used back then were panclasite
filled aircraft bombs.
Ever hear of an explosive train ?
Shells explode when their fuzes set off the filler.
The reasoning of the British was to breach the
hull to sink the vessel. The reasoning of the
Germans was to set the vessel ablaze.
Dealers choice.

Anyway after Jutland both saw little action.

____________________________________

Please lets not turn this into another PA " sensitivity " thread
That on going dispute can be argued here _

http://www.sciencemadness.org/talk/viewthread.php?tid=13187

.

quicksilver - 18-7-2011 at 07:29

Sandia National Labs did a great deal of work on what was NOT 'Ideal" when examining defense systems toward both terror and "standardized warfare".
In fact, some of the most common definitions utilized today & examinations of utilitarian energetics originate from Sandia.

There is a great deal of information via SNL.

[Edited on 18-7-2011 by quicksilver]

Rosco Bodine - 18-7-2011 at 07:46

PA is energetic materials 101. You either know some good information about it or
else you only think you know what you have read, a lot of which information isn't really knowledge but only regurgitated error masquerading as knowledge. And because our friend AH has a tendency might I say to reach a bit far beyond literature which may or may not even be understood, we get a rich mixture there of what is known and what is not known absent any clear distinction. So no, it is not my purpose to make debate anew about what there really isn't any debate, but to underscore the overreaching theory that can occur absent fact checking.
There is a difference between getting a lot of things right and being expert enough to teach and I particularly dislike the knowledgeable professorial tone from those who know a fair amount about some things they are talking while obviously to everyone but themselves don't know shit about the rest, but just keep talking like they don't know when that boundary has been crossed between what they actually do know and what they actually only surmise to be so... but which may not be so at all.

Oxygen balance vs Q

The WiZard is In - 18-7-2011 at 08:05



Oxygen-balance---Q.jpg - 114kB


djh
---
It is interesting to note that for some
primary explosives, like lead azide, lead
styphnate, and mercury fulminate--and
secondary explosives, like PETN and
TNT--that the secondary explosives melt
at a temperature below the point at
which they normally explode, whereas
the primary explosives explode below
the temperature at which they melt,
This may help to explain the marked
difference in sensitivity between the
two types of explosive. However,
melting point alone cannot explain the
differences in sensitivity of pure
secondary explosives; for example, ....

AMCP 706-180

franklyn - 18-7-2011 at 10:02

Attachment: Relationship between Brisance of Explosives and their Molecular Atomic Structures.pdf (890kB)
This file has been downloaded 1000 times

franklyn - 18-7-2011 at 10:27

Regarding oxygen balance it is very succinctly stated by AndersHoveland
" most all common explosives in use have relied almost exclusively on this single property.
But to design better molecules for the future, the horizons will have to be expanded. It is
much more difficult to synthesize molecules which incorporate the other strategies, however."

An interesting question that remains to be resolved is whether it is better
on the whole to pursue zero oxygen balance or forego this in favor of
producing a somewhat greater number of molecular detonation products.
Here is an example :

Tetracyanoethylene is a commercially available reagent.
- Heat of formation = + 148 Kcal/ mol, average of three values
Given it's electron deficit character as observed here _
www.nature.com/nature/journal/v199/n4892/abs/199483a0.html
it should readily undergo cycloaddition with another unsaturated
olefin such as Tetranitroethylene to form TetranitroTetracyanoCyclobutane.

Tetranitro Tetracyano Cyclobutane.GIF - 14kB

Detonation of that yields 12 gas mols per molecule.
If two of the nitriles are replaced ( somehow ) with nitro groups , that
compound is oxygen balanced , but detonation yields just 10 gas mols
however the heat of explosion is twice greater. A rough comparison

- 94 Kcal/ mol for CO2 , 6 CO2 , is - 564

- 26.4 Kcal/ mol for CO , 8 CO , is - 211


Tetracyanoethylene
www.wolframalpha.com/entities/chemicals/tetracyanoethylene/6...
http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=1263...
www.chemicalbook.com/ProductChemicalPropertiesCB9854093_EN.h...
http://webbook.nist.gov/cgi/cbook.cgi?Name=TCNE&Units=SI
www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv4p0877
www.dtic.mil/docs/citations/ADA197044

Tetranitroethylene is very difficult to make and even more unstable than
Tetracyanoethylene , deteriorating away in a matter of days.
I can find no data as to Heat of formation , I estimate it at + 16 Kcal/ mol
A, Villiers, Bull. Soc Chim., 43, 322-324
T. S. Griffin and K. Baum, J. Org. Chem., 45, 2880 (1980)
K. Baun and D. Tzeng, J. Org. Chem., 50, 2736 (1985)

Tetranitroethylene was generated from hexanitroethane in the presence
of anthracene in refluxing benzene and in the presence of cyclopentadiene
in methylene chloride at -1O ºC.

Baum and Tzeng synthesized Tetranitroethylene in 50% yield via the flash vacuum
pyrolysis of hexanitroethane. The optimum conditions for the synthesis involve
passing hexanitroethane vapor, at 1 mm Hg, through a pyrolysis tube heated to
240-270 °C and condensing the product, a greenish yellow solid, in a cold trap.

Nitrocarbons - Arnold T. Nielsen , ed.
www.amazon.com/Nitrocarbons-Organic-Chemistry-Arnold-Nielsen...
Tetranitroethylene is discussed in Chapter 3 , page 87 preparation , page 89 properties

Heats of formation
http://garfield.chem.elte.hu/Burcat/burcat_old/hf.doc

.

hissingnoise - 19-7-2011 at 12:49

Quote: Originally posted by franklyn  
(panclasite)

Misspellings are pretty toxic to credibility - and rightly so . . .

AndersHoveland - 19-7-2011 at 19:27

Quote: Originally posted by AndersHoveland  

It is only the triple bond between two nitrogen atoms that is stronger ( only slightly ) than a
carbon-nitrogen triple bond.


Because the carbon-nitrogen triple bond is nearly as strong a the triple bond in diatomic nitrogen, it does not make much sense to incorporate cyano- groups into explosives.
Such groups would also potentially create toxicity problems (unless they are in the form of a polymer)

The formation of N2 from --CN groups will not release much more energy than it took to break the carbon-nitrogen triple bond. Adding --CN groups to the molecule is therefore somewhat analogous to attaching a canister of highly compressed nitrogen gas to the explosive. Yes, it will add to the explosion, but it additional energy will be almost entirely entropic, which is to say that the nitrogen gas will just occupy a greater volume when it is allowed to expand. This is in sharp contrast to tetrazoles, where the liberation of nitrogen corresponds to the formation of the strong nitrogen-nitrogen triple bond, which lends plenty of energy (which is mostly utilized expanding the gas products).

[Edited on 20-7-2011 by AndersHoveland]

PHILOU Zrealone - 19-7-2011 at 23:40

Quote: Originally posted by AndersHoveland  

Because the carbon-nitrogen triple bond is nearly as strong a the triple bond in diatomic nitrogen, it does not make much sense to incorporate cyano- groups into explosives.
Such groups would also potentially create toxicity problems (unless they are in the form of a polymer)

The formation of N2 from --CN groups will not release much more energy than it took to break the carbon-nitrogen triple bond. Adding --CN groups to the molecule is therefore somewhat analogous to attaching a canister of highly compressed nitrogen gas to the explosive. Yes, it will add to the explosion, but it additional energy will be almost entirely entropic, which is to say that the nitrogen gas will just occupy a greater volume when it is allowed to expand. This is in sharp contrast to tetrazoles, where the liberation of nitrogen corresponds to the formation of the strong nitrogen-nitrogen triple bond, which lends plenty of energy (which is mostly utilized expanding the gas products).

How then do you account for the fact the following organic nitriles/cyanides are mostly if not all endothermic and displays very high flame temperature?
H-C#C-H FT 3100°C (just put here as comparative example)
H-C#N FT over 3500°C
N#C-C#N FT over 4000°C
N#C-C#C-C#N FT over 4700°C
Carbon subnitride - dicyanoacetylen
Please note the high density and high heat of formation...

This and many other examples have brought me to the idea Hydrogen atom in a molecule is not very beneficial to explosive power while multiple bond do contribute to higher densities and entrapped energy.
Simply compare cyclohexane and benzene over density and heat of combustion.

Also you are a bit preaching against your religion...because if we look further tetrazole, triazoles etc that you love so much are only the result of a condensation between azido and cyano groups and the cyclisation into an aromatic like latice/fashion...

I'm quite sure that salts of H-C#C-C#N with AgNO3 or AgClO4 must be sensitive killers as compared to silver acetylide nitrate double salt...It will display higher VODs and brisance.

Two other good challenge are H-C#C-C(NO2)3 (must be able to make sensitive very powerful initiators salts) and the probably very dense (O2N)3C-C#C-C#C-C(NO2)3 ...
Yeah perfect OB, zero hydrogen and multiple bonds providing very high heat of detonation...blocked linear shape providing high density because no move is allowed except external rotation of the nitroformyl moieties...

Franklyn has wel understood their potential as ingredient to increase inherent power.

The -C#N radical is listed in the explosophoric groups and that's for sure for a reason.

If someone has data on the heat of formation or of burning of
CH3-C#N (acetonitrile)
CH2(-C#N)2 (malononitrile - methylene dinitrile - methylene cyanide)
CH(-C#N)3 (cyanooform -nitriloform - tricyanomethane)
C(-C#N)4 (tetracyanomethane)
This would prove to all what Franklyn and I have the intuition of.

[Edited on 20-7-2011 by PHILOU Zrealone]

[Edited on 20-7-2011 by PHILOU Zrealone]

[Edited on 20-7-2011 by PHILOU Zrealone]

AndersHoveland - 20-7-2011 at 11:33

I knew you were going to bring that up.
Strategies for achieving high flame temperature are not necessarily the same strategies that should be used for improving explosive performance, although there is some overlap.

In my opinion, at least, the cyano groups in NΞC–CΞC–CΞN function more as non-hydrogen groups. If desiring to have a high flame temperature, incorporation of hydrogen into the fuel molecule would not be ideal, as the water molecules that form will absorb a significant quantity of heat. Not only does H2O absorb significant energy for its phase change (to steam), but more molecular vibrations are possible in the H2O molecule than the N2 molecule, thus much of the heat is taken up vibrating the molecule instead of expanding the gas.

Such an argument could also be extended towards designing energetic compounds, but there are several reasons this can be problematic. Explosive molecules without hydrogen atoms tend to be more sensitive, and less energetic per unit mass. Since hydrogen atoms have a small size, it can also be a way to pack fuel into a molecule without taking up as much volume, potentially leading to higher energy density.

Combining carbon-carbon triple bonds and trinitromethyl groups is likely to lead to very high sensitivities, if not chemical instability. Although trinitromethane itself is only about as sensitive as picric acid, mixtures with other organic compounds are much more dangerous. Frozen mixtures of trinitromethane with 2-propanol (10%) explode when thawed. Mixtures with divinyl ketone, which contains unsaturated carbon bonds that are more vulnerable to oxidation, can explode at 4°C ! Note that the hydrogen atom in trinitromethane greatly adds to thermal stability, without it the trinitromethyl group is much more liable to partially decompose giving off oxides of nitrogen in storage. The oxides of nitrogen will spontaneously react with the carbon-carbon triple bond, likely leading to significant degredation problems, or even danger of a spontaneous run-away reaction that could initiate detonation in storage (like trinitroanaline) ! Although trinitromethane will oxidize Fe+2 to Fe+3 (indicating it would probably be incompatible with alkynes), the trinitromethyl group (attached to another carbon atom) is in some ways much more inert (for example it is not vulnerable to acid hydrolysis). However, trinitromethyl groups will nevertheless slowly decompose in hot water. Yes, no doubt such compounds would be extremely powerful, but the question is safety and stability.


quote by PHILOU Zrealone: "other examples have brought me to the idea Hydrogen atom in a molecule is not very beneficial to explosive power while multiple bond do contribute to higher densities and entrapped energy. Simply compare cyclohexane and benzene over density and heat of combustion."

This is not really the best example. Benzene probably has a higher density because the molecules are planar, and there is more intermolecular attraction between the molecules because of the unique delocalized nature, in some respects almost similar to metallic bonding. Cyclohexane contains more potential energy of combustion per unit mass than benzene, not only because of the lightweight hydrogen, but also because the hexagonal aromatic ring in benzene is so stable.


quote by PHILOU Zrealone: "Also you are a bit preaching against your religion...because if we look further tetrazole, triazoles etc that you love so much are only the result of a condensation between azido and cyano groups and the cyclisation into an aromatic..."

It is true that I have "preached" against cyano and azido groups; however, when cyclized together into a tetrazole, the properties change. Much of the energetic nature of the azido group is conserved while the sensitivity is markedly reduced. The carbon-nitrogen triple bond turns into much weaker "one single and one double" carbon-nitrogen bond.
The pentagonal ring provides some ring strain, while the aromatic nature adds stability. Tetrazoles also contain an NH group within the ring that is electron-donating, adding stability especially when an electron-withdrawing nitro or nitrimino group is present. This NH group, containing only one nitrogen-hydrogen bond, is more energetic than the usual amine NH2 group often used to stabilize aromatic explosives. The NH group in triazole rings is also much more resistant to oxidation, potentially reducing the complexity of extreme nitrations/oxidations during synthesis.

As for high flame temperatures, you may be interested in the cyclic alkynes, which consist of large rings of carbon atoms alternating between single and triple bonds. It is difficult to find anything online about them, but I remember reading of their preparation in a chemistry journal from the 1980's.
"Cyclo[18] carbon is a highly reactive compound containing an 18-membered ring with alternating single and triple bonds." (botton of p3) http://www.uiowa.edu/~c004121/notes/ch11_3.pdf
http://www.sciencemag.org/content/245/4922/1088.abstract
http://en.wikipedia.org/wiki/Cyclocarbon

[Edited on 20-7-2011 by AndersHoveland]

AndersHoveland - 20-7-2011 at 13:00

I want to mention my strong belief in the promise of using 1,2,3-triazoles in the design of future energetic compounds. Unfortunately, the synthesis of 1,2,3-triazoles is fairly complex (much more difficult than 1,2,4-triazoles) and there is not much information available about an easy synthesis, or the properties of its derivitives.

1,2,3-triazole itself is surprisingly relatively insensitive, and can be safely shipped. 1,2,3-triazole dervitives are also more thermally stable and resistant to hydrolysis than 1,2,4-triazole. 1,2,3-triazole explosives would also be expected to be much more powerful than either 1,2,4-triazoles or 1,2,4,6-tetrazines. 1,2,4,6-tetrazine (C2H2N4), although containing one more nitrogen atom than triazole (C2N3H3), contains much more carbon-nitrogen bonds (in addition the hexagonal aromatic ring is extremely stable), such that it is not really any more energetic than plain hydrazine.

The 1,2,3-triazole ring is very much comparable to tetrazole, except the extra carbon atom allows two energetic groups to be attached to the ring, instead of just one.

[Edited on 20-7-2011 by AndersHoveland]

AndersHoveland - 21-7-2011 at 14:06

(already posted a link to the below, but wanted to actually include it in this forum)

I have designed some potential target molecules that may eventually lead to new explosives which are both safer and more powerful. While the synthesis is probably beyond most of the readers here, I nevertheless wanted to share these ideas with the forum.

4-nitro,5,6-triazolo-1,2,3-triazine-2,7-N-dioxide (NTTO), C3N7HO4
may likely be as powerful as octonitrocubane, while being less sensitive than HMX
https://sites.google.com/site/ecpreparation/ntto

Furoxanyltriazole oxide (FTO), C2N5HO3
could potentially exceed HMX in performance, while being a safer explosive, being significantly more resistant to impact.
https://sites.google.com/site/energeticscribble/furoxanyltri...
https://sites.google.com/site/ecpreparation/fto

TEAN, C6H9N7O6
a molecule with some similarities to RDX, but with a caged structure. Like another experimental energetic compound, TEX, it should be less sensitive, and somewhat more powerful than RDX. The pressence of a tertiary amine on the molecule opens up the possibilities of even more powerful derivitives, either an N-oxide, or possibly even nitrate salts.
https://sites.google.com/site/ecpreparation/tean

N,N’-azoxy-4,4’-bis[5-nitro-1,2,3-triazole]-1-oxide
a bridged triazole compound that would be more powerful than HMX, and possibly somewhat more resistant to impact. It should be fairly easy to prepare from energetic precursors that are already well described in recent publications.
https://sites.google.com/site/ecpreparation/oxidizing-antz

4,8-diamino-3,7-dinitro-1,2,5,6-tetraazobicyclo octene (ANTAZBO),
or alternatively the central adjoining double pentagonal-ringed frame could be described as
pyrrolo[2,1-c]-1,2,3-triazole (PT), or even more accurately as
1,2,5,6-tetrazocyclooctatetraene.
The molecular structure can be described as C4N4(NH2)2(NO2)2
This molecule is based on a frame with a similar structure to 3,6-Dinitropyrazolo[4,3-c]pyrazole (DNPP), which is an energetic compound that has already be prepared adescribed in literature. Unlike DNPP, however, the carbons in the center have been switched with nitrogens from the outside, allowing four side groups to be bonded to carbon atoms, instead of only two. This compound should be relatively insensitive, white at the same time having excellent performance, approaching the power of HMX. With 3 nitro groups instead of two, and one less amino group, it would likely be even more powerful than HMX, although it would then be significantly more sensitive, lsoing some of its resistance to impact.
https://sites.google.com/site/energeticscribble/1-2-5-6-azob...

5,5,6,6-tetranitro-2,3-diazobicyclo[2.1,1]hexane (NDZBH), C4H2N6O8
a caged molecule, similar to 1,1,3,3-tetranitrocyclobutane, but with a diazo bridge that adds both more nitrogen and a large ammount of molecular strain. you can view the skeletal structure (without the four nitro groups) of 2,3-diazobicyclo[2.1,1]hexane here http://energetic.proboards.com/index.cgi?action=downloadatta...
For a comparison, here is some information about 1,1,3,3-tetranitrocyclobutane: estimated detonation pressure between 372-400 kbar, density 1.83 g/mL, melting point 165 degC (not considered melt-castable, significant decomposition), acronym TNCB, performance somewhat better than HMX. Like TNAZ, which has been thoroughly studied, TNCB would be expected to show good thermal stability, despite the geminal nitro groups, because of the ring strain preventing ionization and concurrent carbon-carbon double bonds. TNCB is almost certainly less sensitive than HMX, as TNAZ is fairly insensitive. The diazo bridge, --N=N--, in DNZBH, however would add sensitivity, so it is difficult to speculate on how it would compare to HMX.

It is quite probable that NDZBH would be comparable to octonitrocubane in power.
[I]note about structure[/I]: despite the nitro groups in the 5- and 6- positions, they are not vicinal since the carbons in the
"5-" and "6-" positions in the cage's nomenclature are [U]not[/U] bonded to eachother. In other words, there are two geminal nitro groups on each carbon in the square ring that is not bonded to the other two nitrogen atoms.
https://sites.google.com/site/ecpreparation/2-3-diazobicyclo...

simply RED - 22-7-2011 at 06:47

An unsolvable problem presents the fact that the oxidizer groups -NO2, -O-NO2, =N-NO2 have electron withdraw effect such as the good fuel groups -CN, -C3bondsC-. This makes a molecule having both groups extremely unstable.
For example dinitroacetylene if existed would be unstable.

[Edited on 22-7-2011 by simply RED]

AndersHoveland - 22-7-2011 at 15:09

Quote: Originally posted by simply RED  
An unsolvable problem presents the fact that the oxidizer groups –NO2, –O–NO2, =N-NO2 have electron withdraw effect such as the good fuel groups –CN, –CΞC–. This makes a molecule having both groups extremely unstable.
For example dinitroacetylene if existed would be unstable.


I would not say a molecule is unstable because it has all electron-withdrawing groups, just that oxidizing groups in energetic molecules tend to make the compound more sensitive if there is not some other group that can be electron donating towards it. Even with the nitramine explosive RDX, the inner nitrogen atoms are probably somewhat electron donating towards the nitro groups. This electron donating effect would be expected to be reduced if the methylene groups (-CH2-) only had one hydrogen on them, or if a methylene group were replaced by a carbonyl group -C(=O)-, as for example in "keto-RDX". The nitrimino group =N-NO2 is typically much less unstable without the electron donation effect. The nitrimino group could actually be more "acurately" written as
–N=NO2[-], and thus it can be seen the strong similarity of the group to a nitrate anion. I really have no idea why dinitroacetylene has so far evaded synthesis, or what its sensitivity would be. It may be possible that the molecule would spontaneously polymerize because of the additional presence of nitro groups.

The following may be helpful if wishing to type molecular structures:
Ξ greek letter "xi"
— "em dash"
– "en dash"
- hyphen
If you cannot figure out how to type the symbols using your key board, you can always use the "copy" and "paste" method.

[Edited on 22-7-2011 by AndersHoveland]

Rosco Bodine - 22-7-2011 at 15:31

@AH, Confession is good for the soul. So tell us if you have ever synthesized RDX,
much less any of the more exotic energetic theoretical materials whose technical challenge you estimate is beyond the ability of those you regard as your students here at the SM forum, the economic impracticality of some of these proposed materials for your envisioned powder monkeys of the future notwithstanding.

Name that tune while you are at it

http://www.youtube.com/watch?v=5WsRuzWsZ1s

hissingnoise - 23-7-2011 at 01:13

Why should he not have prepared RDX - dropping hexamine into nitric acid isn't exactly difficult?


Bridged Heterocyclium Di-Cationic closo-Icosahedral ....

The WiZard is In - 23-7-2011 at 06:40

Have stumbled upon this. There dobe a SL of papers
published every year on new explosives &c.

Accession Number : ADA521182

Title : Bridged Heterocyclium Di-Cationic closo-Icosahedral
Perfluoroborane, Borane, and Carborane Salts via Aqueous, Open-
Air Benchtop Synthesis (Preprint)

Descriptive Note : Journal article

Corporate Author : AIR FORCE RESEARCH LAB EDWARDS AFB CA
PROPULSION DIRECTORATE

Personal Author(s) : Shackelford, Scott A. ; Belletire, John L. ;
Boatz, Jerry A. ; Schneider, Stefan ; Wheaton, Amanda K. ;
Wight, Brett A. ; Ammon, Herman L. ; Peryshkov, Dmitry V. ;
Strauss, Steven H.

Handle / proxy Url : http://handle.dtic.mil/100.2/ADA521182

Report Date : 11 MAR 2010

Pagination or Media Count : 30

Abstract : Thirteen unreported bridged triazolium and imidazolium
di-cationic salts, that uniquely pair closo-icosahedral
perfluoroborane [B12F12](exp 2-), borane [B12H12](exp 2-), or
carborane [CB11H12](exp -) anionic species with unsaturated
bridged heterocyclium di-cations, were synthesized in water using
an open-air benchtop method. This considerably extends the
scope of a reported aqueous synthesis of binary
[Heterocyclium]2[B12H12] and [Heterocyclium][CB11H12] salts.
Also, the one-step preparation of five new precursor bridged
heterocyclium di-cationic di-halide salts using conventional
procedures, and in one case a microwave-assisted procedure, is described.

Descriptors : *SALTS, *BORANES, MOLECULAR STRUCTURE,
AQUEOUS SOLUTIONS, CARBORANES, SYNTHESIS(CHEMISTRY),
CRYSTAL STRUCTURE

Subject Categories : ORGANIC CHEMISTRY PHYSICAL CHEMISTRY

Compared to neutral organic compounds, heterocyclic
salts enhance the flexibility to attain rational structural
design, and resultant predicted ingredient properties, that
can permit a tailorable behavioral response.1,2 Tailoring
thermal initiation of heterocyclium borane and di-nitrate
salts to an air-sustained combustion is one example,2 as is
explained by a current initiation sensitivity concept.3

Heterocyclic Salt Synthesis and Rational Properties Tailoring

The WiZard is In - 23-7-2011 at 07:01

Accession Number : ADA513619

Title : Heterocyclic Salt Synthesis and Rational Properties Tailoring (PREPRINT)

Descriptive Note : Journal article preprint

Corporate Author : AIR FORCE RESEARCH LAB EDWARDS AFB CA
PROPULSION DIRECTORATE

Personal Author(s) : Shackelford, Scott A. ; Belletire, John L.

Handle / proxy Url :

Report Date : 23 JUN 2009

Pagination or Media Count : 23

Abstract : Chemical structure determines the inherent properties
displayed by a given compound, and these properties, in turn,
produce a specific performance behavior. Rationally designing
chemical structure to predictably modify compound properties,
such that performance behavior can be tailored in a controlled
manner, defines the objective of a pertinent synthesis effort.
Achieving this objective by introducing structural alterations in a
neutral covalent compound offers only one approach for resultant
properties modification. Heterocyclic salts significantly enhance the
flexibility for achieving properties modification via three strategic
approaches: (1) compositionally pairing various cation structural
classes with a number of anion structural classes, (2)
systematically altering the structure of the cation; and, (3)
systematically altering the structure of the anion. To illustrate this
premise, four general synthesis methods to synthesize heterocyclic
salts, including several new binary heterocyclium icosahedral
closo-borane and closo-carborane salts, first are outlined.
Secondly, properties modification approaches of neutral covalent compounds are then compared with those approaches available for various heterocyclic salts. Lastly, a key example, using three
unsaturated bridged heterocyclium di-cation salts, demonstrates
how rational structure design, and its effect on resultant
predictable properties modification, produces tailored performance
behavior to reach the thermochemical initiation threshold needed
for combustion. This is achieved with predictable properties
modifications that increase salt energy content, or that accelerate
the reaction kinetics of the thermochemical initiation process.


Descriptors : *REACTION KINETICS, *HETEROCYCLIC
COMPOUNDS, *PROPELLANTS, *ENERGETIC PROPERTIES, *SALTS,
*MODIFICATION, *MOLECULAR STRUCTURE,
*SYNTHESIS(CHEMISTRY), BEHAVIOR, ANIONS, CARBORANES,
THERMOCHEMISTRY, COMBUSTION, ENERGY, COVALENT BONDS,
THRESHOLD EFFECTS, NEUTRAL, BORANES, CATIONS,
PREDICTIONS

Subject Categories : ORGANIC CHEMISTRY
PHYSICAL CHEMISTRY
ROCKET PROPELLANTS

Heterocyclic Salt Synthesis and Rational Properties Tailoring

The WiZard is In - 23-7-2011 at 07:09

I have to do a better job of tying my shoe laces in the
future I keep stumbling across things.

Accession Number : ADA513619
Title : Heterocyclic Salt Synthesis and Rational Properties Tailoring (PREPRINT)
Descriptive Note : Journal article preprint
Corporate Author : AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
Personal Author(s) : Shackelford, Scott A. ; Belletire, John L.

Handle / proxy Url : http://handle.dtic.mil/100.2/ADA513619

Report Date : 23 JUN 2009

Pagination or Media Count : 23

Abstract : Chemical structure determines the inherent properties
displayed by a given compound, and these properties, in turn,
produce a specific performance behavior. Rationally designing
chemical structure to predictably modify compound properties,
such that performance behavior can be tailored in a controlled
manner, defines the objective of a pertinent synthesis effort.
Achieving this objective by introducing structural alterations in a
neutral covalent compound offers only one approach for resultant
properties modification. Heterocyclic salts significantly enhance the
flexibility for achieving properties modification via three strategic
approaches: (1) compositionally pairing various cation structural
classes with a number of anion structural classes, (2)
systematically altering the structure of the cation; and, (3)
systematically altering the structure of the anion. To illustrate this
premise, four general synthesis methods to synthesize heterocyclic
salts, including several new binary heterocyclium icosahedral
closo-borane and closo-carborane salts, first are outlined.
Secondly, properties modification approaches of neutral covalent
compounds are then compared with those approaches available for
various heterocyclic salts. Lastly, a key example, using three
unsaturated bridged heterocyclium di-cation salts, demonstrates
how rational structure design, and its effect on resultant
predictable properties modification, produces tailored performance
behavior to reach the thermochemical initiation threshold needed
for combustion. This is achieved with predictable properties
modifications that increase salt energy content, or that accelerate
the reaction kinetics of the thermochemical initiation process.

Descriptors : *REACTION KINETICS, *HETEROCYCLIC
COMPOUNDS, *PROPELLANTS, *ENERGETIC PROPERTIES, *SALTS,
*MODIFICATION, *MOLECULAR STRUCTURE,
*SYNTHESIS(CHEMISTRY), BEHAVIOR, ANIONS, CARBORANES,
THERMOCHEMISTRY, COMBUSTION, ENERGY, COVALENT BONDS,
THRESHOLD EFFECTS, NEUTRAL, BORANES, CATIONS,
PREDICTIONS

Subject Categories : ORGANIC CHEMISTRY
PHYSICAL CHEMISTRY
ROCKET PROPELLANTS

1,3,5,5-Tetranitrohexahydropyrimidine (DNNC)

The WiZard is In - 23-7-2011 at 07:18

Elucidation of such mechanistic features should aid in the
structural design of new high energy compounds with improved
thermochemical properties.

Accession Number : ADA491044

Title : Liquid State Thermochemical Decomposition of Neat
1,3,5,5-Tetranitrohexahydropyrimidine (DNNC) and its DNNC-d2,
DNNC-d4, DNNC-d6 Structural Isotopomers: Mechanistic Entrance
into the DNNC Molecule

Descriptive Note : Journal article

Corporate Author : AIR FORCE RESEARCH LAB EDWARDS AFB CA
PROPULSION DIRECTORATE

Personal Author(s) : Shackelford, S. A. ; Menapace, J. A. ; Goldman, J. F.

Handle / proxy Url : http://handle.dtic.mil/100.2/ADA491044

Report Date : 25 NOV 2007

Pagination or Media Count : 19

Abstract : Global kinetics for the liquid state thermochemical
decomposition of neat 1,3,5,5-tetranitrohexahydropyrimidine
(DNNC), perdeuterio-labeled DNNC-d6, and partially deuterium-
labeled DNNC-d2 and DNNC-d4 isotopomers were obtained by
isothermal differential scanning calorimetry (IDSC). Molecular
kinetic deuterium isotope effect (KDIE) values obtained with DNNC
and DNNC-d6 from 174 to 194-deg C revealed that C-H bond
rupture regulates both an endothermic catalytic initiation and the
exothermic propagation of the liquid thermochemical
decomposition process. Using IDSC-based KDIE comparisons with
the DNNC-d2, DNNC-d4, and DNNC-d6 isotopomers, a more
detailed chemical structure/mechanistic relationship emerged by
entering the interior of the DNNC molecule. Here structural kinetic
KDIE results showed the rate-controlling C-H bond rupture has its
origin at the non-equivalent C-2 methylene group sandwiched
between the two nitrated DNNC nitrogen ring atoms, versus at the
chemically equivalent C-4 and C-6 methylene ring positions
located elsewhere in the DNNC molecule. Elucidation of such
mechanistic features should aid in the structural design of new high
energy compounds with improved thermochemical properties. A
170.0 kJ/mol activation energy appeared for the endothermic
induction period, and a lower 104.2 kJ/mol activation energy was
determined for the exothermic acceleratory portion of the DNNC
decomposition process. The global liquid and solid state
thermochemical decomposition processes for DNNC are compared.


Descriptors : *KINETICS, *DECOMPOSITION,
*THERMOCHEMISTRY, ISOTOPES, MOLECULAR STRUCTURE,
DEUTERIUM, DIFFERENTIAL SCANNING CALORIMETRY,
PYRIMIDINES, REPRINTS, ISOTHERMS, ENDOTHERMIC
REACTIONS, NITRO RADICALS, LIQUIDS, EXOTHERMIC
REACTIONS

Subject Categories : PHYSICAL CHEMISTRY MECHANICS


djh
----
And thus ends today stumbling, I will now go forth into my 180+
acre wood lot to there wander aimlessly while — mumbling
incoherently, gesticulating wildly and drooling.

Role of Thermochemical Decomposition in Energetic Material Initiation Sensitivity and Explosive Performance

The WiZard is In - 25-7-2011 at 09:14

Accession Number : ADA468050
Title : Role of Thermochemical Decomposition in Energetic
Material Initiation Sensitivity and Explosive Performance
Descriptive Note : Conference paper (preprint)
Corporate Author : AIR FORCE RESEARCH LAB EDWARDS AFB CA
Personal Author(s) : Shackelford, Scott A.
Handle / proxy Url : http://handle.dtic.mil/100.2/ADA468050
Report Date : 05 FEB 2007
Pagination or Media Count : 31
Abstract : Catastrophic initiation of an energetic material consists
of a complex, interactive, sequential train of mechanistic
mechanical, physical, and chemical processes which occur over a
finite time period and proceed from macroscopic into sub-
microscopic composition levels (bulk > crystalline > molecular >
atomic). Initiation results when these processes proceed at a rate
which generates sufficient energy (heat) to reach a threshold stage
within this finite time period. Thus, the rate at which these
mechanistic processes occur defines initiation sensitivity and
affects performance. Thermochemical decomposition processes
regulate the rate at which heat energy is released at the molecular
level, and therefore to some extent, control energetic material
initiation sensitivity and performance characteristics. Kinetic
deuterium isotope effect (KDIE) data, obtained during ambient
pressure thermochemical decomposition process, identifies the
mechanistic rate-controlling bond rupture which ultimately
regulates the energy release rate of a given energetic material.
This same rate-controlling bond rupture also appears as a
significant rate-limiting feature in higher order deflagration,
combustion, and explosion phenomena. The effect the KDIE-
determined rate-controlling bond rupture exerts on initiation
sensitivity, and its potential influence in combustion and explosion
performance is delineated.
Descriptors : *SENSITIVITY, *EXPLOSIVES,
*THERMOCHEMISTRY, *DECOMPOSITION, *ENERGETIC
PROPERTIES, SYMPOSIA, ISOTOPE EFFECT, KINETICS,
DEUTERIUM, MATERIALS, RATES
Subject Categories : PHYSICAL CHEMISTRY AMMUNITION AND
EXPLOSIVES

AndersHoveland - 5-8-2011 at 02:28

this is just more conjecture, but wanted to discuss the pyrrolo[2,1-c]-1,2,3-triazole based molecule ("ANTAZBO"), which was proposed in my previous post in this thread. the attached picture shows some of the different resonance structures, which would have a strong stabilizing effect on the rings and nitro groups. This is indicative that the compound would have relatively low sensitivity. The electron donating effect also is one of the reasons for the insensitive nature of triaminotrinitrobenzene, which is the chemical explosive used in nuclear weapons for this same reason. Fox-7 is another example were the electron-donating effect is key to the molecule's stability.

(B) should have low sensitivity, with excellent performance

(C) even with three nitro groups on the molecule, the compound would liklely not be too sensitive

(F) in this resonance structure both adjacent nitro groups have extra electrons, which greatly increases stability, otherwise two adjacent nitro group on an aromatic ring typically increases sensitivity of the compound

0056g.GIF - 14kB

A clearer version of the same picture can be seen here:
https://3462015841141507561-a-1802744773732722657-s-sites.go...



also wanted to include the idea for a potential synthesis again,
005.GIF - 6kB

This would be somewhat similar to the procedure that has already been done by
R.A. Carboni, J.C. Kauer, J. American Chem. Society, volume 89, p2633, (1967).
although their reaction would not have been complicated by equilibrium with the tetrazole.

[Edited on 5-8-2011 by AndersHoveland]

PHILOU Zrealone - 23-9-2011 at 13:29

Quoted from Anders Hoveland
I want to mention my strong belief in the promise of using 1,2,3-triazoles in the design of future energetic compounds. Unfortunately, the synthesis of 1,2,3-triazoles is fairly complex (much more difficult than 1,2,4-triazoles) and there is not much information available about an easy synthesis, or the properties of its derivitives.
End of Quote
A simple way to 1,2,3 triazoles is via ortho-diaminobenzene and nitrous acid!
(the C=C being part of an aromatic ring!)
NH2-C=C-NH2 + HO-N=O --> O=N-NH-C=C-NH2 + H2O
O=N-NH-C=C-NH2 <--> HO-N=N-C=C-NH2
HO-N=N-C=C-NH2 --> cyclo(-N=N-C=C-NH-)


[Edited on 23-9-2011 by PHILOU Zrealone]

AndersHoveland - 24-9-2011 at 15:14

Quote: Originally posted by PHILOU Zrealone  

A simple way to 1,2,3 triazoles is via ortho-diaminobenzene and nitrous acid!
(the C=C being part of an aromatic ring!)
NH2-C=C-NH2 + HO-N=O --> O=N-NH-C=C-NH2 + H2O
O=N-NH-C=C-NH2 <--> HO-N=N-C=C-NH2
HO-N=N-C=C-NH2 --> cyclo(-N=N-C=C-NH-)


Yes, but then you are stuck with an unwieldy benzene ring to your triazole. Not to say that benzene rings are inherently bad, but because benzene has so much carbon, it is hard to make benzene derivitives compete with the newer more powerful explosives.

I know this reaction is correct, as I have seen it before, but can you share the specific reference source with us?

[Edited on 24-9-2011 by AndersHoveland]

franklyn - 18-12-2011 at 16:00

Back to Basics
Molecular Structure & Performance of High Explosives.pdf

Attachment: Molecular Structure & Performance of High Explosives.pdf (488kB)
This file has been downloaded 843 times

Lambda-Eyde - 18-12-2011 at 17:15

Quote: Originally posted by AndersHoveland  

I know this reaction is correct, as I have seen it before, but can you share the specific reference source with us?

The Wikipedia article on benzotriazole gives the following reference for the synthesis:

Robert A. Smiley “Phenylene- and Toluenediamines” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_405

[Edited on 19-12-2011 by Lambda-Eyde]

killswitch - 18-12-2011 at 19:05

This might seem a little weird or off topic, but has anyone tried feeding explosive precursors to various microorganisms to see if they shit out anything useful? There must be some chemosynthetic organism somewhere that makes an energy profit from oxidation of amines. Perhaps they carry an enzyme or two with interesting properties.

franklyn - 27-12-2011 at 23:07


@ killswitch
http://www.sciencemadness.org/talk/viewthread.php?tid=10976#...
http://www.sciencemadness.org/talk/viewthread.php?tid=4380&a...

________________________________________________________


HCN is endothermic having a Heat of Formation of + 32.3 Kcal/ mol , ~ +1196.3 Kcal/ Kg

Heat of formation , + 32.3 for HCN ( g ) , - 57.8 for H2O ( g ) , - 94 for CO2
. . . . . . . . . . . . . . . . . 4 HCN + 5 O2 . .=>. . 2 H2O . . . . . + . . . . . 4 CO2 . . . . + . . . . 2 N2
. . . . . . . . . . . . . . . . . .+129.2 . . . . . . . . . . . . - 115.6 . . . . . . . . . . . .- 376

The heat of reaction for the balanced equation as shown is - 620.8 kilocalories
Dividing that by the coeficient 4 , the heat of combustion of HCN works out to -155.2 kilocalories / mol , ~ - 5748 Kcal/ Kg

The weight of HCN + oxygen constituents is , 4(27) + 10(16) = 268

1000 x ( 620.8 ÷ 268 ) = 2 3 1 6 Kcal/ Kg for the oxygen balanced mixture

For comparison the energy obtained from NH4NO3 + 2 Al => Al2O3 + N2 + 2 H2

is ~ - 2900 Kcal/ Kg , twice that of glyceryl trinitrate

_______________________________________

What can be inferred from the above excercise is that the energy of a reaction is
derived from the fuel portion , the oxidizer unless it has some energy endothermically,
is just as much dead weght as unburned fuel. H2O2 has a density of 1.432 gm/cc in
98% strength, while liquid O2 at normal boiling point has a density of 1.142 gm/cc. .
Even with hydrogen included, H2O2 has 18 % more oxygen per unit volume than
liquid O2 ! Extra energy is also additionally provided by it's endothermicity. The low
output of ANFO ( NH4NO3 + fuel oil ) is directly attributable to the low fuel content
~ 6 % of the weight. This also illustrates why Sprengel type explosive mixtures have
greater energy since the fuel is not partially " burned " by a bond attaching the oxidizer
functional group. The Heat of Formation of Triazine the trimer of HCN , is + 41 ,
markedly less than the sum of the three individual HCN constituents , which
demonstrates the loss which occurs from bonding. A stable moiety made up of X
number of HCN constituents + Oxygen in the mol ratio of 2C 2H 2N 5O will obtain
close to maximum possible energy output. Glycol Dinitrate C2H4N2O6 for example
approximates the stated ratio and achieves ~ 1500 Kcal/ Kg. Nitrocarbons devoid of
hydrogen achieve the greatest energy product , ~ 1800 Kcal/ Kg for Hexanitrobenzene.
The molecular properties particularly density , as well as number of gas products will
determine the detonation characteristics of the explosive.
Having highly endothermic fuel moieties attached with oxidizing functional groups
leads to inevitable sensitivity if not actual instability. In the second half of this post
www.sciencemadness.org/talk/viewthread.php?tid=1970&page...
I outlined a method of circumventing that by having the groups separated in the
form of their ionic salts , then crystallized together.

.

AndersHoveland - 27-12-2011 at 23:18

The CΞN triple bond is significantly stronger than than the C=N double bond. If one wishes to incorporate nitrogen into the molecule, it is preferable not to have the nitrogen atom already triple-bonded.
Quote: Originally posted by franklyn  
An interesting question that remains to be resolved is whether it is better
on the whole to pursue zero oxygen balance or forego this in favor of producing a somewhat greater number of molecular detonation products.


Interesting and important question. My opinion about this is that explosives that decompose into CO2 tend to be somewhat more powerful than when the decomposition product is mostly CO, but the difference does not seem to be big. Of course it depends very much on how the nitrogen is bonded to begin with, but the formation of N2 seems to be potentially better than either CO or CO2, but not extremely so. Considering the sensitivity versus power tradeoffs, I am rather partial to explosives that contain a mix of CO and CO2 in their decomposition products, with the nitrogen in the original molecule mostly being used to hold oxygen, and optionally with one NH or NH2 group to serve as an electron donor (resulting in a reduction of sensitivity) and making the molecule more polar (also decreasing sensitivity and typically allowing closer molecular packing, increasing density).

[Edited on 28-12-2011 by AndersHoveland]

franklyn - 28-12-2011 at 02:11

@ AndersHoveland
Quote:
The CΞN triple bond is significantly stronger than than the C=N double bond.
If one wishes to incorporate nitrogen into the molecule, it is preferable not
to have the nitrogen atom already triple-bonded.

You still don't get it , even after PHILOU Zrealone exhaustively explained it.
The falacy of your assertion cannot be more stark than seen in the example I gave
above of the heat of formation of 3 HCN molecules relative to the heat of formation
of one trimer of the same three. 3 (+ 32) against 1 (+ 41).

Bond energies .gif - 24kB

Bond energies as referenced above
CΞN , 891
C=N , 615
C=C , 611
C -C , 347
C -N , 293
N -N , 159


Taking the bonding of two adjacent atoms in isolation of the whole molecule
does not characterize it.
Please observe your dangling particles , -CΞN , =C=N-
There is no possible arrangement of bonds other than CΞN that does not
produce a higher enthalpy !

CN.gif - 5kB

N=C=N -C , (615 + 615 + 293) = 1523
C=C=N -C , (611 + 615 + 293) = 1519
N=C=N -N , (615 + 615 + 159) = 1389
C=C=N -N , (611 + 615 + 159) = 1385

C -CΞN , (347 + 891) = 1238
N -CΞN , (293 + 891) = 1184

.

AndersHoveland - 28-12-2011 at 06:41

Look at the attached diagram. (Obviously we are disregarding bond strain. It is only a diagram. The only reason it is in a square is to avoid making it overcomplicated :P )

In both arrangements, the two carbon atoms and two nitrogen atoms are all completely bonded with eachother. The net bonding energy of cyanogen, which contains the carbon-nitrogen triple bonds, is 2129. But the net bonding energy is lower in the lower configuration, at exactly 2000. Lower bond energy means the initial bonds are easier to break, so conversely the explosive will be more energetic.

Am I misunderstanding something?

CNbonding01.png - 5kB

franklyn - 28-12-2011 at 14:11

Okay , leave it to you to tender an example to bolster your contention.
Take as an example another hypothetical molecule NΞC-NO2
essentially replacing the H in HCN with NO2. Just as in the example
of the trimer of 3 HCN , the trimer of 3 NΞC-NO2 , Trinitrotriazine
forms at greater enthalpy ( but not by much).
Bond strain is mostly pertinent to carbon to carbon bonding since a
strained nitrogen to nitrogen bond is easily broken , in fact isomerism
will impede their stable formation and defeat such arrangement reducing
the molecules energy , which will otherwise be too sensitive for practical
application. Perhaps you are on to something regarding the new mostly
nitrogen species being investigated made up with some carbon atoms,
clearly in such case your observation is justified , but may not provide
all that much advantage after all compared to more familiar formations.
See => Tris Tetrazolo Triazine < = > Cyanuric Triazide
http://www.sciencemadness.org/talk/viewthread.php?tid=4094#p...

Resonant bonding is perhaps why furoxans are so energetic despite
the low oxygen balance. Observing also that the achieved density greatly
factors into the equation , such as in NTTO and some variations proposed
by you elsewhere.
http://www.sciencemadness.org/talk/viewthread.php?tid=1970&a...
Synthesis of New High-Oxygen Carriers & Ditetrazinetetroxide (DTTO)
www.dtic.mil/dtic/tr/fulltext/u2/a513104.pdf

.

AndersHoveland - 28-12-2011 at 14:46

Of course, 1,3,5-triazine is not an ideal scaffold for explosive molecules. The ring is aromatic, and that makes the bonding much stronger. In addition, better to have more nitrogen-nitrogen bonds (double or single), because they are much weaker. And of course, trinitrotriazine is merely a theoretical molecule. The compound has never been isolated, and would not be expected to be chemically stable.

The good thing about resonance is that it generally results in reduced sensitivity, which is an important consideration when trying to stick on as much nitrogen or nitro groups as possible. Resonance also can affect chemical properties, typically making a ring scaffold easier to chemically alter.

[Edited on 28-12-2011 by AndersHoveland]

AndersHoveland - 12-1-2012 at 13:50

Quote: Originally posted by killswitch  
This might seem a little weird or off topic, but has anyone tried feeding explosive precursors to various microorganisms to see if they shit out anything useful?


http://www.ncbi.nlm.nih.gov/pmc/articles/PMC110595/

Anaerobic microorganisms (found in common "municipal sludge" :P ) can reduce either 1 or 2 of the nitramine groups in RDX to nitrosamines (one less oxygen atom). Other microbial end degredation products included nitrous oxide, methanol, formic acid, methane, and carbon dioxide.

AndersHoveland - 17-1-2012 at 16:22

I just had a thought.

Although 1,1,3,3-tetranitro-cyclobutane is not considered melt-castable (there is significant decomposition at its 165 °C melting point), perhaps 1,1,3-trinitrocyclobutane would be melt-castable.

trinitrocyclobutane.png - 5kB

A structurally similar compound, 1,3,3-trinitroazetidine (TNAZ) is melt-castable, having a melting point of 101-103 °C.

Trinitrocyclobutane could potentially be a high-performance replacement for TNT. Just compare molecular formulas,
C4H5(NO2)3
C7H6(NO2)3 for TNT

And unlike the synthesis for TNAZ, preparing cyclobutane derivitives could potentially be much more straightforward.

Partial condensation of formaldehyde with nitromethane under alkaline conditions to obtain 2-nitroethanol (note that 2-nitroethanol is toxic and can potentially be absorbed through skin contact). 2-nitroethanol then distilled with conc. H3PO4 and NaBr to give 1-nitro-2-bromoethane. This is then cyclized to 1,3-dinitrocyclobutane in a procedure similiar the one used by Wade (synthesis trans-1.2-Dinitrocyclopropane (DNCP) ).

see the thread in this forum, "1,2-dinitro cyclopropane and nitric acid?" or use the link below,
Quote: Originally posted by Pulverulescent  

2.6 Synthesis of Compound 6: trans-1.2-Dinitrocyclopropane (DNCP).
Wade and co-workers' procedure<sup>9</sup> for the synthesis of trans-1,2-dinitrocyclopropane


An oxidative nitration could then be done to add the third nitro group, 60% yield, using a mixture of sodium nitrite and sodium persulfate in the presence of potassium ferricyanide*, or in 39% yield with a mixture of sodium nitrite and silver nitrate.

*This procedure is similar to the synthesis of 1,1-dinitroethane from nitroethane, the details of which can be found in this forum.


For comparison, 1,1,3,3-tetranitro-cyclobutane has a density 1.83 g/mL, while TNAZ has a density of 1.84 g/mL. I cannot find any reported values, but 1,1,3,3-tetranitro-cyclobutane is probably slightly more powerful than HMX.



[Edited on 18-1-2012 by AndersHoveland]

Pulverulescent - 19-1-2012 at 01:13

"Giver of Bad Advice"?
Ha-Ha-Ha-Ha-Ha-Ha-Ha-Ha-Ha-Ha-Ha-Ha-Ha-Ha-Cough! Hack! Choke!
Giver of emphysema─ by default . . . :D

P

AndersHoveland - 19-1-2012 at 15:53

Quote: Originally posted by AndersHoveland  
1-nitro-2-bromoethane. This is then cyclized to 1,3-dinitrocyclobutane in a procedure similiar the one used by Wade (synthesis trans-1.2-Dinitrocyclopropane (DNCP) ).


I would like to post one potential correction. Reaction of 1-nitro-2-bromoethane with a base may also likely just yield nitroethylene, but this intermediate should still be able to condense with another alkaline nitroalkane. It might be a better idea not to brominate the whole portion of the 2-nitroethanol all together in the earlier step.

NO2-CH=CH2 + [-]NO2=CH2-CH2-OH --> [-]O2N=CH-CH2-CH(-NO2)-CH2-OH

(There are mentions in the literature of nitroethylene, or 1,1-dinitroethylene, condensing under alkaline conditions with formalin, which is just another name for formaldehyde. The literature also mentions "condensation of piperylene with nitroethylene". So these types of reactions are fairly characteristic of nitroethylene.)

[-]O2N=CH-CH2-CH(-NO2)-CH2-OH --> conc. H3PO4, NaBr --> NO2-CH2-CH2-CH(-NO2)-CH2-Br

The latter compound could then be cyclized [into the cyclobutane derivitive] by being made alkaline again with sodium acetate.


I also added a diagram in the other thread to help clarify the chemistry of these types of reactions.
Quote: Originally posted by AndersHoveland  


I would like to discuss the basic chemistry related to the
"Synthesis of Compound 6: trans-1.2-Dinitrocyclopropane"
nitroalanehalogenreactions.png - 4kB



another side note of lesser importance,
Quote: Originally posted by AndersHoveland  

An oxidative nitration could then be done to add the third nitro group, 60% yield, using a mixture of sodium nitrite and sodium persulfate in the presence of potassium ferricyanide*.

Some other sources in the literature say that this reaction does not work on 1,3-dinitrocylcobutane, but other sources give conflicting information. The literature clearly shows it to work with azetidine compounds, so there is no reason it should not also work on cyclobutane derivitives.

It is also very important that water not be present if the nitrocyclobutane derivitives are made alkaline. Just as is the case with nitromethane, the presence of water results in more complex reactions.

also see
"Hydrogenolytic Denitration of Polynitro Compounds",
Raja Duddua, Paritosh R. Davea, Reddy Damavarapub, Rao Surapanenib & Richard Gilardic, pp 2709-2714, Synthetic Communications, Volume 35, Issue 20, 2005

[Edited on 20-1-2012 by AndersHoveland]

AndersHoveland - 16-2-2012 at 19:26

Quote: Originally posted by Formatik  

what is better for an energetic then, to have an oxidizing moiety or high nitrogen content?


Consider this: The bond dissociation energy of carbon monoxide is 1072 kJ/mol, which is higher than even that of diatomic nitrogen N2 at 942 kJ/mol.

In practice, however, carbon and oxygen stored in a molecule are usually already bound with more strength than nitrogen is. A single nitrogen-nitrogen bond is also much weaker than bonds between other atoms. So theoretically a high nitrogen content can be better. But in practice, taking either approach to an extreme, either all nitrogen, or all fuel-oxidizer, is likely to result in higher sensitivities.

It may be ideal to have at least one nitrogen (better with 1 or 2 hydrogen atoms on it) act as an electron donating group toward a nitrogenous ring or nitro groups, adding stability and reducing sensitivity.

5,5′-hydrazinebistetrazole, C2N10H4, does not have any oxygen atoms, and has a detonation velocity of around 7200-7400 m/sec (if I remember correctly), and has a relatively low sensitivity, (sensitivity to shock under 30 J, friction value under 108 N). HCN forms as one of the main decomposition products.

[Edited on 17-2-2012 by AndersHoveland]