deltaH
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nitrodiphenylmethanes
I was thinking of TNT analogues and a thought occurred to me, perhaps diphenylmethane could be nitrated to yield a higher molecular weight TNT
analogue.
Giumanini, et al. (2002) reports the formation of a mixture of isomers of dinitro-diphenylmethane with "negligible" side reactions [1].
Oddly, they don't report further nitration.
Ideally for energetics, one would want much higher nitro products though... I wonder if this cannot be obtained with more aggressive nitration
conditions, especially as no side reactions occurred with the dinitro- product.
Steric hindrance is perhaps the problem, though the molecule is already fairly twisted.
The nice thing about diphenylmethane is that it can be prepared from benzyl chloride and benzene, catalysed by AlCl3 [2], so that's not too exotic.
Reference:
[1] Giumanini, AG et al. (2002). Nitration of Diphenylmethane and the Isomeric Nitrodiphenylmethanes in Dichloromethane. Ind. Eng. Chem.
Res., 41 (8), 1929–1934.
[2] Hartman, WW & Phillips, R. (1943). Diphenylmethane, Org. Synth.; Coll. 2 (232).
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deltaH
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I have found a second reference by the same author, Giumanini et al (2002) in The Chemical Educator [1]. One can see the first two
pages of this article for free here which includes the experimental section. Interestingly, they describe how much safer this is than a benzene nitration and how it generates
less waste and such, making it suitable for classroom labs. That's a plus for amateur experimentation as well.
Reference:
[1] Giumanini, AG. et al. (2002). The Chemical Educator. A Convenient ar-SE Laboratory Experiment Avoiding the Use of
Sulfuric Acid: the Nitration of Diphenylmethane in Ch2Cl2, The Chemical Educator, 7(1), 27-32.
[Edited on 13-1-2015 by deltaH]
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Praxichys
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You are right. It looks as if steric hindrance inhibits nitration past the 2,4 positions on either side. I think that it would be difficult, if not
impossible to further nitrate the compound.
TNT has 3 nitro groups and a methyl group per benzene ring and the compound in question would have two nitro groups and half a methyl group per
benzene ring.
(NO2)3C6H5(CH3)
C7H8N3O6 --> 4H2O + CO2 + 6C + 1.5N2
(NO2)2C6H5(CH2)C6H5(NO2)2
C13H12N4O8 --> 6H2O + CO2 + 12C + 2N2
The oxygen balance for the proposed compound is really awful. I think this would behave much like dinitrotoluene as they are nearly the same
empirically. Very insensitive, but also a pretty terrible explosive and likely difficult to fully detonate.
It might serve well as a fuel for mixtures with AN or something.
If you like the shape, perhaps look into 2,2',4,4' tetranitro- derivatives of diphenylamine, diphenylnitramine, and azobenzene?
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deltaH
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Just had a look at the nitration of triphenylmethane just to see what happens there. Could only find mention in a book online that it forms the
trinitro derivative (one nitro per ring) which can be reduced to make a dye.
I'm still wondering whether these substances cannot be nitrated further... the nitration done, at least in the case of diphenylmethane, seem very
mild... it would appear on purpose to avoid "dangerous" compounds  TNT itself
requires fairly aggressive conditions to trinitrate.
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CuReUS
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I think WFNA/RFNA with oleum at high temperature will nitrate it
you could also try using fuming HNO3 with BF3 as,BF3 reacts with nitric acid to form nitronium tetrafluoride,which is
a useful nitrating agent
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Praxichys
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A more amateur-friendly solution is N2O5 in chloroform.
It is fairly easily prepared by gassing a chloroform solution of silver nitrate with chlorine and decanting the silver chloride precipitate.
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deltaH
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Wow Praxichys, that is one neat trick  Thanks for sharing!
[Edited on 14-1-2015 by deltaH]
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DubaiAmateurRocketry
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Quote: Originally posted by Praxichys  | A more amateur-friendly solution is N2O5 in chloroform.
It is fairly easily prepared by gassing a chloroform solution of silver nitrate with chlorine and decanting the silver chloride precipitate.
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whats a good way to prepare N2O5 - chlorohydrocarbon mixtures?
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APO
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Any references for that N2O5 in chloroform prep? That sounds really great.
"Damn it George! I told you not to drop me!"
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Praxichys
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Brauer makes mention of it on pp. 490.
| Quote: | Other preparative methods: From AgNO3 and Cl2 or from
AgNO3 and POCl3. |
Also the last page of this document (which you might find interesting anyway):
http://www.scripps.edu/4C51200E-EFC7-4CBB-93A8-EB3FAEAF4302/...
Henri Étienne Sainte-Claire Deville (1818-1881) was the first to prepare it, and used this method to apparently isolate the solid. I cannot find any
experimental procedures at the moment, but I imagine that it may not be documented since it probably proceeds quantitatively. Measures may need to be
taken to prevent over-chlorination to nitryl chloride. It is certainly prepared as cold as possible.
SPECULATION WARNING: PERFORM AT YOUR OWN RISK
I imagine dissolving chlorine into a pre-weighed flask of chloroform to get an exact amount, then adding an amount of AgNO3 in chloroform to that
flask. Everything would be pre-cooled with dry ice/acetone and the addition performed slowly.
The compound to be nitrated would then be dissolved in chloroform and this solution dripped slowly into the N2O5 bath with careful temperature
monitoring. Be aware that too cold is just as dangerous as too hot - it can allow the reaction to be so slow that reactants build up until a
temperature is reached that causes runaway. Also be aware that there will be a concentration of organics/N2O5 that will become detonable, and I am not
sure whether CHCl3 could form a detonable mix with N2O5. Dilution is key.
After the reaction, any excess N2O5 is converted to HNO3 with the addition of water and then is extracted and neutralized in the aqueous layer. The
AgCl2 can be filtered at this point, and the chloroform boiled/evaporated off to reveal the final product.
If the final product is not soluble in chloroform, the AgCl2 would need to be settled and the N2O5 solution decanted prior to the nitration. I omitted
this above since N2O5 continuously decomposes with time and handling.
If the stuff to be nitrated is not soluble in chloroform, it might be able to be slowly added as a pure solid or liquid, but this poses issues with
contact area. It would work if the nitrated product was soluble in chloroform, otherwise incomplete nitration is likely.
If the highly-nitrated compound is too water-sensitive for aqueous workup, the N2O5 might be destroyed by simply warming the flask to reflux prior to
removing the solvent. You would, however, be potentially concentrating a powerful high explosive mixed with N2O5, unless you could verify all the N2O5
was destroyed prior to solvent removal. This could cause a serious explosion.
Since this is a nasty procedure just to add another NO2 group, it would be advisable to first nitrate the compound as much as possible with fuming
nitric/conc sulfuric and collecting the mostly-nitrated product before giving it the N2O5 treatment. Of course, this has the unfortunate consequence
of making nearly every material used in the N2O5 procedure explosive.
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deltaH
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Thanks Praxichys for your input, it is much appreciated. I enjoyed reading your hypothetical synthetic methodology.
The suggestions so far appear themed around 'super' nitrators, nitronium salts, N2O5 and other animals.
100% Nitric acid in acetic anhydride is another really strong nitrator that has not yet been mentioned, however, I'm wondering if this
diphenylmethane, probably having very similar properties to toluene, cannot 'simple' be nitrated by conventional TNT recipes at high temperature...
starting (analogously) by first forming the mono- or di- nitro derivative by mild means. The mono-nitro derivative does not appear to be explosive as
it's been published in an educational journal.
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DubaiAmateurRocketry
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Wow, I take chemistry class in that university. Is there any alternative? because AgNO3 is very expensive.
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deltaH
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Hey DubaiAmateurRocketry, your username has just reminded me, perhaps higher nitrodiphenylmethanes could be useful in propellant
formulations. I would imagine they probably have a much higher melting point than TNT, but enjoy a high degree of insensitivity?
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DubaiAmateurRocketry
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umm in the past I also thought about these compounds as additives in formulations, but i later realized its not the best propellant, because the gas
molecules produced upon combustion of these series of EM does not give a low enough average gas molecular weight to be better than existing
propellant. For me, I always look for higher hydrogen content, then nitrogen, then oxygen, and carbon would come last and best if not existent in the
formulation.
I think there is a curve where the Isp directly relates to CHON weight % of an CHON EM, where the higher the H%, and lower the C% would be better
unless there is a large heat of formation difference or bad oxygen balance, simply because carbon eats too much oxygen, and produces heavier gases
than hydrogen.
If 2 different formulations one containing high H% and the other one with low H% and high C%, and the high C% formulation manage to have the same Isp,
you can almost certainly conclude the one with high H% would be better because it would have a lower combustion temperature than the one with the
higher C%. I usually compare a new EM to RDX at once if its almost oxygen balanced, comparing the CHON %. If there is a high H% I would look more into
it. Diphenylmethane for example, if you manage to nitrate it and put 6 nitro groups into this molecule, becoming C13H6(NO2)6, its oxygen content would
be 1.38% by weight, while its oxygen negative. Lets see RDX now, C3H6N6O6, with 2.723 % H by weight and not OB negative (in terms of CO). So RDX is
better than hexanitrodiphenylmethane, and its almost ruled out in my opinion :p
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Praxichys
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The silver is easily recovered and re-used. Other methods I think will use labware which is far more expensive.
One can treat N2O4 with ozone to get N2O5.
Brauer details the action of P2O5 on 100% HNO3, kept cold, and distilled under pure oxygen with 6-7% ozone.
AgNO3 on POCl3 is also mentioned, but of course that still uses AgNO3.
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DubaiAmateurRocketry
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Umm, assuming HNO3 could dissolve in chloroform/dichloromethane, can you simply add P2O5 and have a solution of N2O5 in it? I wonder how do you get
rid of the phosphoric acid? I forgot where I read it, or if its true, but I heard phosphoric acid prevent nitration?? which is why N2O5 in H3PO4 would
not work as a nitration mixture?
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deltaH
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DubaiAmateurRocketry, I'm not sure I understand you meaning exactly.
EM's like TNT that have poor OB can produce a larger amount of hydrogen gas in their products, which is good for ISP. At the same time its lower
energy content is bad for ISP... but I wouldn't be able to say that TNT has a lower ISP than RDX for certain without doing some model calculations.
One would need the adiabatic flame temperature and composition of gases from a TNT decomposition and RDX decomposition in order to do the ISP
calculation.
Do you have data on adiabatic flame temperature and composition of gases perhaps?
Otherwise, this could be estimated using the open source software COCO as I have done in my thread about 'dimethylcyanamide' as a substitute for
USDMH.
[Edited on 15-1-2015 by deltaH]
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deltaH
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Synthesis of diphenylmethane
Diphenylmethane can be prepared very simply from benzyl chloride, benzene and the slow addition of anhydrous AlCl3 over 15-20 minutes in an ice
bucket [2], without the need to reflux as was traditionally done [1]. This was found to eliminate formation of anthracene by-product. [2]
A water trap, to absorb the evolved HCl, is required.
References:
[1] Vogel. A.I., Practical Organic Chemistry, 3rd ed., Longmans,
London, 1961, pp. 513-4.
Note: Available from the SM library.
[2] Ellis, WD. (1963). Preparation of diphenylmethane. Simplified procedure: purer product. J. Chem. Educ. 40(7), p 346.
Note: Available from references.
[Edited on 16-1-2015 by deltaH]
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PHILOU Zrealone
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@DeltaH,
I will come back on this tread later and deeper...
Diphenylmethane might also result from more common and less lachrymatory stuffs (than benzyl chloride):
AlCl3, CH2Cl2 and benzene ratio 1/2 with a slight exces of benzene to avoid C6H4(CH2)2C6H4 and multimers (Ar-CH2-Ar-CH2-Ar, ...).
[Edited on 17-1-2015 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
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deltaH
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Thank you PHILOU Zrealone for the mention of an alternative and I look forward to your input, as always.
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