| Pages:
1
2 |
IodineForLunch
Harmless
Posts: 34
Registered: 28-8-2002
Location: NJ
Member Is Offline
Mood: bored
|
|
Nitrosyl Perchlorate
Found a substance called nitrosyl perchlorate (NOClO4.H2O) while browsing the CRC Chem Handbook today. I tried to figure out its synthesis process,
and this is the best I've come up with:
2NaNO2 + 2HCl --> NO2 + NO + 2NaCl + H2O
Bubble the resulting gas through perchloric acid:
NO2 + NO + 2HClO4 --> 2NOClO4.H2O
This substance decomposes at 100 degrees Celsius, and in contact with water (not counting its water of hydration), and will explode if mixed with
ethyl alcohol. Perhaps a mixture of perchloric acid and sulfuric acid could be used to keep the excess water to a minimum.
This substance could possibly be detonated, and is probably a damn strong oxidizer.
Thoughts?
David Hansen
|
|
|
Psycho
Harmless
Posts: 42
Registered: 17-9-2002
Location: <-----------
Member Is Offline
Mood: No Mood
|
|
Wierd. I conducted the first equation you have to form Nitrogen Dioxide Gas for a CHEM 101 Lab.
2NaNO2 + 2HCl --> 2NaCl + H2O + NO2 + NO.
I asked my lab instructor and she said that the amount of NO produced is very small.
Is that true?
|
|
|
madscientist
National Hazard
Posts: 962
Registered: 19-5-2002
Location: American Midwest
Member Is Offline
Mood: pyrophoric
|
|
Nitrosyl chloride, NOCl, is formed by reacting HNO3 with HCl. I suppose that the reaction proceeds like this:
HNO3 + HCl ----> H2O + O2NCl
O2NCl + 2HCl ----> H2O + NOCl + Cl2
I wouldn't be suprised if nitrosyl perchlorate could be prepared from nitric acid and perchloric acid. That reaction may be dangerous if concentrated
reactants are used!
HNO3 + HClO4 ----> H2O + O2NClO4
O2NClO4 + 2HClO4 ----> ONClO4 + HClO4 + HClO3
HClO3 is quite unstable, existing only in dilute solution... so reaction of concentrated HNO3 with concentrated HClO4 easily could be explosive.
I weep at the sight of flaming acetic anhydride.
|
|
|
IodineForLunch
Harmless
Posts: 34
Registered: 28-8-2002
Location: NJ
Member Is Offline
Mood: bored
|
|
Or...
2HClO4 + 2HNO3 --> 2ONClO4 + 2H2O + O2
Once again, sulfuric acid might help to remove excess water.
David Hansen
|
|
|
madscientist
National Hazard
Posts: 962
Registered: 19-5-2002
Location: American Midwest
Member Is Offline
Mood: pyrophoric
|
|
Uh, your equation isn't balanced. 
I would think that perchloric acid would be dehydrated by sulfuric acid to Cl2O7, a very dangerous, explosive, oxidizing liquid.
I weep at the sight of flaming acetic anhydride.
|
|
|
madscientist
National Hazard
Posts: 962
Registered: 19-5-2002
Location: American Midwest
Member Is Offline
Mood: pyrophoric
|
|
Never mind, the equation IS balanced, for some reason I was seeing 2ONClO4 but thinking 2O2NClO4....
I weep at the sight of flaming acetic anhydride.
|
|
|
IodineForLunch
Harmless
Posts: 34
Registered: 28-8-2002
Location: NJ
Member Is Offline
Mood: bored
|
|
Why isn't nitric acid dehydrated by sulfuric acid into various nitrogen oxides?
David Hansen
|
|
|
madscientist
National Hazard
Posts: 962
Registered: 19-5-2002
Location: American Midwest
Member Is Offline
Mood: pyrophoric
|
|
HNO3 is dehydrated to N2O5, an unstable crystalline solid.
When HNO3 is mixed with concentrated H2SO4 the resulting mixed acid contains large quantities of the nitronium ion:
NO2+.
I weep at the sight of flaming acetic anhydride.
|
|
|
PHILOU Zrealone
International Hazard
Posts: 2893
Registered: 20-5-2002
Location: Brussel
Member Is Offline
Mood: Bis-diazo-dinitro-hydroquinonic
|
|
Cl-NO + AgClO4 --> AgCl + ON-ClO4
N2O3 + Cl2O7 --> 2 ON-ClO4
2 HNO2 --> H2O + NO + NO2 (N2O3)
NO + 1/2 O2 --> NO2
(NO doesn't stand air exposure!)
ON-ClO4 + H2O --> HNO2 + HClO4
HClO4 + HNO3 --> O2N-O-Cl2O6 + H2O
2HNO3 + SO3 --> H2SO4 + N2O5
6HClO4 + P2O5 --> 3Cl2O7 + 2H3PO4
The making and use of Cl2O7 is very hard and dangerous!
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
|
|
|
Theoretic
National Hazard
Posts: 776
Registered: 17-6-2003
Location: London, the Land of Sun, Summer and Snow
Member Is Offline
Mood: eating the souls of dust mites
|
|
Hmmm... Quote:
"Nitrosyl perchlorate can be prepared by passing a mixture of nitric oxide gas and nitrogen dioxide gas into 72% perchloric acid in an Erlenmeyer
flask. The use of a bubbler can increase the amount of gas that reacts with the acid. Evaporate the resulting mixture until the temperature rises to
140 °C and dense white fumes are evolved, then cool. Over times crystals will precipitate, filter to collect them. The product can be dehydrated in a
vacuum desiccator over phosphorus pentoxide in the desiccator."
Could this be helpful?
Also, about another nitrosyl salt, nitrosyl fulminate. Does it exist, and if so, can it be prepared by the way of:
NOCl+HONC=>NOONC+HCl
(nitrosyl chloride can also be made by reacting NO and Cl2)
NOONC has got a perfect oxygen balance, and sounds like a good explosive.
[Edited on 23-7-2003 by Theoretic]
|
|
|
Nick F
Hazard to Others
Posts: 439
Registered: 7-9-2002
Member Is Offline
Mood: No Mood
|
|
Haha, yeah if you have a bottle of fulminic acid lying around!
Madscientist:
"O2NClO4 + 2HClO4 ----> ONClO4 + HClO4 + HClO3"
Are you sure?
|
|
|
BromicAcid
International Hazard
Posts: 3227
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline
Mood: Rock n' Roll
|
|
I once read a paper on the preparation of anhydrous perchloric acid, they took about one part 70% Perchloric and mixed it with 10 parts 100+% sulfuric
(oleum) and distilled under severerly reduced pressure, the crystals that resulted were an equilibrium mixture of HClO4 and Cl2O7, Kinda interesting.
Anyway, I can't seem to find nitrosyl perchlorate in my chemistry encyclopedia, no surprise but I do have nitronium perchlorate in here, NO2ClO4,
it's formed from ozone, nitrogen dioxide, and chlorine dioxide, highly reactive, soluble in water to nitric and perchloric acids, may explode,
etc. sounds equally interesting as nitrosyl perchlorate.
|
|
|
blip
Hazard to Others
Posts: 133
Registered: 16-3-2003
Member Is Offline
Mood: absorbed
|
|
What about nitryl perchlorate; its formula is the same as nitronium perchlorate but has a peroxide bond. It may not exist because the latter
obviously exists, although they may be the same thing possibly existing in equilibrium.
Bad ASCII drawing of this enormously powerful oxidizing agent:<tt>
O
</tt>||<tt>
O-N-O-O-Cl=O
</tt>||<tt>
O</tt>
[Edited on 7-24-2003 by blip]
|
|
|
Axt
National Hazard
Posts: 778
Registered: 28-1-2003
Member Is Offline
Mood: No Mood
|
|
Nitrosyl Perchlorate
Formula: NOClO4
MW: 129.47
N: 10.82%
OB: +67.97 (anhydrous)
+59.67 (monohydrate)
Density: 2.169 g/cm3
ΔHf: -41.79 ± 0.08kcal/mol
Properties (except OB's) from PATR2700.
OB's calculated to HCl.
Anyone have references to other properties of NOClO4? toxicity? solubility? etc..
<b>Synthesis:</b> N2O3 was generated by mixing 50g of starch (as corn flour) with 100ml 70% nitric acid and 50ml water, this mixture was
heating until red fumes appear. The nitric acid is reduced by the starch liberating the nitrogen oxides in a self sustaining reaction. The gas was run
through a PVC tube into a beaker containing 80ml 70% perchloric acid.
N<sub>2</sub>O<sub>3</sub> + 2 HClO<sub>4</sub> → 2 NOClO<sub>4</sub> +
H<sub>2</sub>O
The HClO4 solution quickly foamed up with the formation of nitrosyl perchlorate monohydrate (NOClO4.H2O), which precipitated as fine white crystals.
Its important to leave a good amount of room in the reaction vessel to accommodate the large quantity of foam that is produced.
<center><img src="http://www.sciencemadness.org/scipics/axt/noclo4synthesis.jpg"></center>
<i>NOTE: PATR, Urbanski & <a
href="http://www.roguesci.org/megalomania/explo/nitrosyl_perchlorate.html">Megalomania</a> (who probably copied it from PATR) give
a synthesis that bubbles N2O3 through HClO4 THEN boil the solution down to retrieve the NOClO4, this seems terribly wrong and is probably an error in
interpretation from the original article, thats been copied down the chain. NOClO4 readily precipitates from concentrated HClO4, and is decomposed if
the solution is boiled. The decanted HClO4 can be reconcentrated by boiling, and this is likely where the error occured.</i>
There is no mention of explosives containing NOClO4 in the literature, nor derivatives from it, only that it will explode in contact with EtOH &
acetone and forms diazonium perchlorates (with explosion) in contact with aromatic primary amines. It decomposed immediately in contact with water,
and cannot be dried when exposed to the atmosphere.
Literature reports the salt can be dehydrated over phosphorous pentoxide, this wasnt available but I did try adding a small amount to concentrated
H2SO4, it seemed stable, no decomposition, didnt dissolve so it may be a way of removing the water of hydration.
NOClO4 seems stable if left under concentrated HClO4. Some NOClO4.H2O was placed into glacial acetic acid, no visible decomposition, but it had
dissappeared by the next day. When placed into nitromethane the NM turned greenish, no noticible decomposition and remained stable for at least 3
days.
A slurry of nitromethane/NOClO4.H2O was made by pouring an excess of NM through HClO4 wet NOClO4, thus flushing the acid out. the excess liquid was
poured off the top and 9ml of the slurry was detonated with 0.5g PETN.
<center><img src="http://www.sciencemadness.org/scipics/axt/nitrosyl-perchlorate-nm.jpg">
<a href="http://ww1.webtop100.net/~62552/xmovies.webtop100.net/banners/xmovies.html">MOVIE</a></center>
The same setup as the PLX & TCED charges, making direct comparisons possible. The NOClO4/NM penetrated the plate, where PLX would not.
Still, NM isn't a desirable fuel for NOClO4, the OB'ed mixture is 60:40 NM/NOClO4.H2O, this isn't possible due to the high percentage
of liquid and high density of NOClO4. A more preferable fuel may be nitrobenzene, or even acetic acid, though the instability of NOClO4 makes any
practical use unlikely. Of course the dehydrated salt would also increase performance.
[Edited on 7-6-2005 by Axt]
|
|
|
artem
Hazard to Self
Posts: 53
Registered: 9-1-2005
Member Is Offline
Mood: No Mood
|
|
This substance is very poorly investigated, for some reason the mixes of NO2ClO4 were investigated more often (in rocket fuels & explosives),
despite of more complex synthesis and practically the same energetic characteristics.
Another value of Hf, known in literature, is +52.3kJ/mole, decomp.108C (140C- intensively) without melting. Hygroscopicity is moderate, that?s why,
probably, dehydratation of NOClO4*H2O is possible without P2O5.
Synthesis from HClO4 is shortly described in ?Handbook?? of Brauer. During this synthesis only 20-30 % of substance drop out as a crystals. To
increase the output (on HClO4) AFTER FILTRATION mother liquor must be boiled and then again reacted with NOx. Another synthesis - N2O3+H2SO4+NaClO4.
The most interesting are mixes with condensed explosives (for example TNT). PVC is suitable as a binder at room temperature.
|
|
|
Axt
National Hazard
Posts: 778
Registered: 28-1-2003
Member Is Offline
Mood: No Mood
|
|
| Quote: | | PVC is suitable as a binder at room temperature. |
Was that in reference to nitrosyl or nitronium perchlorate? I couldnt find detailed info practical applications on either. Only that attempts have
been made and are still being made to use the nitronium salt as a propellant.
I ran a search through JACS, only come up with whats attached.
Confirms some of my observations, such as no effect on NM, cant be left exposed to air and stable with concentrated H2SO4. They use NM to remove the
HClO4 before drying, as HClO4 isn't very volatile. Has a bit on its thermal decomposition as well,
"It was determined in the present work that at 92°, under vacuum (3-5 mm.), weight losses of 27, 61, 94 and l00%, occurred with a 0.5-g. sample
after 3, 6, 9 and 12 hr., respectively. Losses at l00°, under similar conditions, were 65, 80 and 99%. after 3, 6 and 9 hr., respectively."
Their attempts to convert the nitrosyl to nitronium failed.
[Edited on 16-6-2005 by Axt]
Attachment: nitrosyl-perchlorate.pdf (397kB)
This file has been downloaded 1997 times
|
|
|
chemoleo
Biochemicus Energeticus
Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline
Mood: crystalline
|
|
Are the nitrosyl versions of periodic acid, H5IO6 (soluble in H2O, mp 122 deg C, or a better representation is HIO4*2H2O)), or of perbromic acid (I
have no info on this here) known?
They might make more stable derivatives... although the affinity for water is bound to remain a problem.
Interesting work anyway, Axt! I doubt many can say they made nitrosyl perchlorate!
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
|
|
|
Axt
National Hazard
Posts: 778
Registered: 28-1-2003
Member Is Offline
Mood: No Mood
|
|
The fact that artem gave reference to a method using a perchlorate salt in H2SO4 makes it not overly exotic. Does KClO4 dissolve in H2SO4?
Ive seen no references to periodate/perbromate, actually, you had a periodate salt did you not 
I downloaded Bretherick .. very interesting. Nitrosyl azide (N4O  ) lead block
expansion >600ml where NG = 520ml, it's wanting to decompose when over -50°C kinda limits its practical application 
I'll copy/paste the entries for nitrosyl/nitronium perchlorate.
| Quote: |
4027. Nitrosyl perchlorate
[15605-28-4] ClNO5 O:NOClO3 Gerding, H. et al., Chem. Weekbl., 1956, 52, 282–283 Although stable at ambient temperature, it begins to decompose
below 100°C, and at 115–120°C the decomposition becomes a low-order explosion.
Pentaammineazidocobalt(III) perchlorate, Phenyl isocyanate Burmeister, J. L. et al., Chem. Eng. News, 1968, 46(8), 39 During an attempt to introduce
phenyl isocyanate into the Co coordination sphere, a mixture of the 3 components exploded violently when stirring was stopped.
Organic materials
Hofmann, K. A. et al., Ber., 1909, 42, 2031
As the anhydride of nitrous and perchloric acids, it is a very powerful oxidant.
Pinene explodes sharply; acetone and ethanol ignite, then explode; ether evolves gas, then explodes after a few s delay. Small amounts of primary
aromatic
amines–aniline, toluidines, xylidines, mesidine–ignite on contact, while larger
amounts exploded dangerously, probably owing to rapid formation of diazonium
perchlorates. Urea ignites on stirring with the perchlorate, (probably for a similar
reason).
See other NON-METAL PERCHLORATES, OXIDANTS
4028. Nitronium perchlorate
[12051-08-0] ClNO6
O2N+ ClO−4
Albright, Hanson, 1976, 2
The explosively unstable behaviour of stored nitronium perchlorate is attributed to the formation of small equilibrium concentrations of the isomeric
covalent nitryl perchlorate ester (below).
1,2-Epoxides
Golding, P. et al., Tetrahedron Lett., 1988, 29, 2733
Reaction with epoxides gives the dangerously unstable and explosive mixed
nitrate–perchlorate diesters, such as 1,2-ethanediyl nitrate perchlorate from
ethylene oxide.
|
hmm. I have some propylene oxide, wonder if nitrosyl will take on the same reactions as nitronium ( ONO-CH2-CH(ClO4)-CH3 ). Though I know of no suitable solvent. I think I saw that the nitronium salt is
soluble in NM, though carrying out this reaction in a high explosive seems kinda silly. Perhaps olefins will act simulary, (barring explosion) forming
oxime-perchlorates. Unless it wants to dimerise as in the <a
href="http://www.sciencemadness.org/talk/viewthread.php?tid=2960">pseudonitrosites</a> ... pure speculation here.
[Edited on 17-6-2005 by Axt]
|
|
|
artem
Hazard to Self
Posts: 53
Registered: 9-1-2005
Member Is Offline
Mood: No Mood
|
|
Information was about nitrosyl perchlorate (PVC is suitable for nitronium too).
Yes, as for nitronium salt only attempts have been made to use it, but real attempts ? real propellants, measurements of Jsp and so on. But chemical
and thermostability is so poor? As for explosives, I know only about proposals to increase the brisance (up to 40-50GPa) of mixtures by the usage of
high dense explosive fuel and oxidizer ? NO2ClO4, LiClO4, salts NF4+, etc.
As I know, KClO4 dissolve in H2SO4 only at heating, and instead NOClO4 NOHSO4 will be produced. Probably, it is interesting to use SO3+H2SO4 to make
the "dry" solution NOHSO4 then mixing it with 70%HClO4.
About nitrosyl azide ? very interesting, how they measured lead block expansion below ?50C? and what about the reaction NON3+Pb?
Simple calculation give for NON3 Qexpl about 5.2MJ/kg (RDX 5.4-5.6MJ/kg ? 480-500ml expansion), that?s why >600 ml is a mistake or bad measurement.
To Chemoleo: what is the need of salts such as NOBrO4?- it seems to me, they have no special advantages; and BrO4- (and JO4-) may be sufficient strong
oxidizer to react with NO+, giving NO2.
|
|
|
Axt
National Hazard
Posts: 778
Registered: 28-1-2003
Member Is Offline
Mood: No Mood
|
|
Regarding N4O. Dont know, but I dont think calculations will stack up so well against practical tests, especially when comparing completely different
explosive families. Note that their calculations arrived at 6.3 MJ/kg. Its a yellow oil (freezes @ -85°C), thus one would assume they fired a sealed
& chilled capsule inside the lead block. Heres the full extract including references.
| Quote: |
4766. Nitrosyl azide
[62316-46-5] N4O
O:NN3
1. Lucien, H. W., J. Amer. Chem. Soc., 1958, 80, 4458
2. Klap¨otke, T. M., et al., Angew. Chem. (Int.), 1993, 32(11), 1610
3. Tornieporth-Oetting, I. C. et al., Angewand. Chem. (Int.), 1995, 34(5), 511
Explosions were experienced on several occasions during preparation of nitrosyl
azide by various methods [1]. A yellow solid at-85°C, it decomposes even at-50°C [2]. It has an enthalpy of detonation of 6.3 kJ/g, the same as
nitroglycerine, and a cavity volume greater than 600ml in the lead block test (TNT D 300; Nitroglycerine D 520 ml) [3].
|
Another reference that looks to be of interest is:
The Nitrosyl Azide (N4O) Potential Energy Hypersurface: A High Energy-Density Boom or Bust?," Galbraith, J. M.; Schaefer, H. F. J. Am. Chem. Soc.
1996, 118, 4860.
If I can get my car going sometime soon, i'll go get it.
|
|
|
chemoleo
Biochemicus Energeticus
Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline
Mood: crystalline
|
|
Artem, I thought the idea was obvious. Nitrosyl perchlorate dissociates in water, it's highly unstable and reactive. I was hoping that the
respective perbromates/iodates may be a little more stable, at the admitted expense of less oxidising power per gram of material, and probably less
energy release altogether. This isn't necessarily a quest to find the most energetic material out of all, it's a quest to see what's
usable in practical terms, and it's a quest... of having fun with chemistry!
Axt, yes, you are right indeed on my stock situation , I will check how
easy/difficult it is to isolate HIO4*2H2O. Also, aren't periodates much easier to make than perchlorates? Shall check that too.
Oh, and it's not *that* silly to use energetic materials for the synth of even more energetic materials, after all, dinitrourea has been used as
a syntheon for some complex cyclic expl - and dinitrourea is unstable and very energetic in its own right!
[Edited on 20-6-2005 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
|
|
|
Axt
National Hazard
Posts: 778
Registered: 28-1-2003
Member Is Offline
Mood: No Mood
|
|
| Quote: | | Oh, and it's not *that* silly to use energetic materials for the synth of even more energetic materials, |
That wasn't the point, I'm likening it to synthing a hypersensitive detonator inside a solution of HE.. Not the wisest choice of solvent! It
would be interesting to see what solvent they did use --> <i>"Golding, P. et al., Tetrahedron Lett., 1988, 29, 2733"</i>
anyone?
EDIT:
Just saw Mr Wacks link into the journals, withholding my $30, heres the abstract from the above ref.
| Quote: |
Several aziridines and three azekidines have been found to yield nitramine-nitrates in good to excellent yield by ring opening with dinitrogen
pentoxide.
|
Seems its not specific to nitrate-perchlorates anyway, and likely out references to a more relevant article. For the N2O5 reactions they use a
"halogenated solvent". It's probably worth checking the compatibility of DCM with NOClO4.
[Edited on 21-6-2005 by Axt]
|
|
|
Axt
National Hazard
Posts: 778
Registered: 28-1-2003
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by Axt
Perhaps olefins will act simulary, (barring explosion) forming oxime-perchlorates.
|
Did a bit of searching, no finds related to perchlorate addition products to olefins, but I did find one for nitrosyl chloride:
"Work on the addition to olefins of nitrosyl and nitryl chlorides (44, 69, 317,
336,348, 364,380, 404a) is also of value in interpreting the behavior of nitrogen
dioxide."
refs
(44) BECKHAM, L. J., FESSLER, W. A., AND KISE, M. A.: Chem. Revs. 48, 319 (1951).
(69) BRINTZINGER, H., AND PFANNSTIEL, K.: Z. anorg. Chem. 266, 325 (1948).
(317) PRICE, C. C., AND SEARS, C. A.: J. Am. Chem. SOC. 76, 3275 (1953).
(336) RIEBSOMER, J. L.: Chem. Revs. 36, 157 (1945).
(348) SCHECHTER, H., AND CONRAD, F. : J. Am. Chem. SOC. 76, 5610 (1953).
(364) SEEL, F., AND NOGRADI, J.: Z. anorg. Chem. 269, 188, 197 (1952).
(380) STEINKOPF, W., AND KUHNEL, M.: Ber. 76, 1323 (1942).
(404a) TUOT, M.: Compt. rend. 204, 697 (1937).
Attached is the article on nitrosyl azide.
Attachment: nitrosyl-azide.pdf (581kB)
This file has been downloaded 1708 times
|
|
|
woelen
Super Administrator
Posts: 7976
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
Yesterday I unexpectedly received some H5IO6
So, for me it was time to find some of its interesting properties and I stumbled across this thread. Very interesting thread! I only have a very
limited amount of H5IO6, so, before I blindly start playing around with the stuff, I could use some suggestions from other people.
My idea is to make some NO+NO2 (can be made nicely from NaNO2 and acid) and simply lead this over the H5IO6 after drying. The problem is that there
are two molecules of water in the periodic acid.
I already tried dehydrating a tiny pinch of the acid by carefully heating it in a mini-test tube, but apparently this does not work. The acid melts
and then it suddenly starts bubbling vigorously, leaving a white solid behind and water condenses on the cooler part of the test tube. I checked the
gas with a thin glowing tooth-cleaner, it is oxygen, so the periodic acid decomposes. Wikipedia says that H5IO6 can be dehydrated, but apparently
heating is not the way to do that. Does HIO4 exist and is wikipedia wrong? My chemistry book only mentions H5IO6. The white solid, which remains is
I2O5 (both my book and wikipedia say so). Stronger heating gives deep purple vapor of I2.
|
|
|
JohnWW
International Hazard
Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by woelen
My idea is to make some NO+NO2 (can be made nicely from NaNO2 and acid) and simply lead this over the H5IO6 after drying. The problem is that there
are two molecules of water in the periodic acid. I already tried dehydrating a tiny pinch of the acid by carefully heating it in a mini-test tube, but
apparently this does not work. The acid melts and then it suddenly starts bubbling vigorously, leaving a white solid behind and water condenses on the
cooler part of the test tube. I checked the gas with a thin glowing tooth-cleaner, it is oxygen, so the periodic acid decomposes. Wikipedia says that
H5IO6 can be dehydrated, but apparently heating is not the way to do that. Does HIO4 exist and is wikipedia wrong? My chemistry book only mentions
H5IO6. The white solid, which remains is I2O5 (both my book and wikipedia say so). Stronger heating gives deep purple vapor of I2.
|
The octahedral [IO6]5- anion is stereochemically and energetically favored over the tetrahedral IO4-, unlike ClO4- and BrO4-, because the larger size
of the I atom allows more ligands, and because of the much easier availability of empty 6s orbitals (2 electrons), 5d (up to 10 electrons), and 4f
orbitals (up to 14 electrons) to accept pairs of electrons from the O atoms (making a total of 18 valence electrons to be accommodated, 10 in the
previously empty orbitals), compared to the situation with Br and Cl, which do not have available empty f orbitals, only s and d and (at a much higher
energy level) p orbitals. However, octahedrally coordinated Cl(VII) is known, in the cation ClF6+, isoelectronic with SF6 and PF6-, with 12 valence
electrons to be accommodated.
That dehydration and decomposition of H5IO6 to I2O5 instead of I2O7 is contrary to the observation that I(VII) compounds are generally more stable
than I(V) compounds, which tend to disproportionate to give I(VII). Similarly, reaction of F2 with I2 preferentially gives IF7 rather than IF5.
For the same reason, in compounds of Xe(VIII), which are the most stable Xe compounds, H4XeO6 is favored, although XeO4 is known and is still the most
stable Xe oxide. In compounds of Te(VI), [TeO6]6- tends to be favored over [TeO4]2-, unlike Se(VI) and S(VI).
|
|
|
| Pages:
1
2 |
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
