It uses a nitrate salt and hydrochloric acid instead of the usual nitric acid. If it works, it would make the production of HDN much more feasible. I
plan to perform the reaction soon. However, not wanting to waste my reagents, I have a few questions first:
1) Is HDN soluble in cold water? Will the precipitate form as stated? (I think so, but I haven't been able to find any reliable sources.)
2) I know that under certain conditions HCl can decompose hexamine. Will that happen here?
3) Why would HDN form instead of hexamine hydrochloride? Is hexamine hydrochloride more soluble?
If anyone has any experience with this reaction, I would welcome their advice.Motherload - 19-6-2013 at 23:36
From what I understand HCl hydrolyzes hexamine to NH4Cl and formaldehyde. Intergalactic_Captain - 20-6-2013 at 04:53
It works, it's a simple displacement reaction that takes place at a faster rate than the decomposition of hexamine in acid. If you're paranoid about
it, do it backwards - Dissolve your hexamine and nitrate salt, set up for stirring and slowly drip in your HCl. Been too many years since I've tried
it so I don't remember the particulars as to temperature and solubility, but HCl is much more tame and forgiving than H2SO4 when it comes to this type
of reaction.AndersHoveland - 20-6-2013 at 12:35
If using hydrochloric acid with nitrates, be sure the acid concentration is low, otherwise you will have essentially made aqua regia, and
there may be some equilibrium that leads to undesirable chlorination. This can happen even when the HCl is as dilute as 20%, though it may not be an
issue as long as you do not allow the hexamine to soak too long.
I had another thought for making hexamine dinitrate without the nitric acid. Just mix 1 molar equivalent of hexamine with 4 equivalents of NH4NO3 and
6 molar equivalents of formaldehyde. Hexamine disassociates in water to some extent back to CH2O and NH3, the equilibrium preferring condensation
towards hexamine. It should really be rather simple.
[Edited on 20-6-2013 by AndersHoveland]Motherload - 20-6-2013 at 13:03
Wouldn't just mixing NH4NO3 and CH2O solutions form HDN ?
NH3 condenses with CH2O to form hexamine. Adas - 21-6-2013 at 01:23
Wouldn't just mixing NH4NO3 and CH2O solutions form HDN ?
NH3 condenses with CH2O to form hexamine.
That's a very nice idea. Somebody should definitely give it a try.Maniak - 21-6-2013 at 02:14
It will not work in a way you said. You have to add some base otherwise you are not having free NH3. Check GB1548827 Motherload - 21-6-2013 at 08:49
NH4NO3 in anhydrous conditions (AcAn), condenses with CH2O to form RDX.
One would think it would form HDN in aqueous conditions. AndersHoveland - 21-6-2013 at 21:01
Wouldn't just mixing NH4NO3 and CH2O solutions form HDN ?
No, I really do not think so. (with heating it would react, but then you would get an entirely different Leuckart/Eschweiler–Clarke reaction)
Using the proper ratio would be very important if any equilibrium is to proceed. The hexamine cage can only act as a diprotic base. For those two
ammonium ions to be pulled in, the cage also needs two free NH3 molecules to form the C6N4H142+ hexamine
cation.
It will not work in a way you said. You have to add some base otherwise you are not having free NH3.
There is some small equilibrium in solutions of ammonium nitrate. Otherwise it would not be acidic, would it?
But I am sure the presence of acid would prevent any of the NH3 from condensing with any formaldehyde present (assuming there is no Leuckart methylation, but I do not think this starts until around 90°, typically hotter, correct me if wrong)
Ever boiled a solution of ammonium nitrate? One can smell the odor of ammonia.
(short explanation if there was confusion: what was meant by the Leuckart reaction is that the formaldehyde condenses with a NH3 to form a
transient imine, and then another formaldehyde is oxidized to formic acid, further to CO2 in subsequent reaction, while the imine is reduced to an
amine)
So in conclusion, what I am suggesting is that if we put formalin together with ammonium hydroxide, but not quite enough ammonia to soak up all the
formalin, then some NH4NO3 could also be absorbed and condense. But without the ammonia, I do not think any NH4NO3 will be able to be absorbed by the
formalin solution. On the other hand, if too much ammonia is present, it will just form hexamine, as none of the NH4NO3 is pulled in.
If you are unable to accurately measure out the reactants, I would suppose the best course of action would be to just use more NH4NO3 than needed,
since any excess will not interfere, but then you may have difficulty separating out the final product. And use more formaldehyde than can condense
with the ammonium hydroxide present, even if it is greater than the optimal 3:1 ratio. Weigh the initial solid NH4NO3 reactant, and then weigh the
final mixed salt product afterwards to calculate the amount of HDN present.
