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Author: Subject: Formation of Hexamine
tito-o-mac
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Formation of Hexamine

For weeks I've been trying to figure out a way around the formation of Hexamine (C6H12N4). It's used as a solid fuel tablet for cooking.

From some websites I found some tiring way to prepare it: Hexamine is made up of Formaldehyde (CH2O) and ammonia. Ammonia is relatively easy to obtain, except for the Formaldehyde. Here's a method for Formaldehyde I found on Wikipedia: "Industrially, formaldehyde is produced by the catalytic oxidation of methanol. The most common catalysts are silver metal or a mixture of an iron oxide with molybdenum and vanadium. In the more commonly used FORMOX® process methanol and oxygen react at ca 250-400 °C in presence of iron oxide in combination with molybdenium and/or vanadium to produce formaldehyde according to the chemical equation

2 CH3OH + O2 → 2 H2CO + 2 H2O
The silver-based catalyst is usually operated at a higher temperature, about 650 °C. On it, two chemical reactions simultaneously produce formaldehyde: the one shown above, and the dehydrogenation reaction

CH3OH → H2CO + H2
Formaldehyde is readily oxidized by atmospheric oxygen to form formic acid. Formic acid is found in ppm levels in commercial formaldehyde." Too complicated and difficult!

Is there another easier way to figure this out?
hashashan
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This process to produce hexamine proves out to be highly non-economical. You will need lots of ammonia and Formaldehyde in order to obtain a segnificant ammount of hexamine.
i used something like 200ml(after the mix of both) and the result was something like half a teaspoon of hexamine.
not_important
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Given your location, why bothe rto make it? India has several large produces of hexamine, Iran and China export it, and Russia and Saudi Arabia are large scale producers. As hexamine is much easier to store and transport than the raw materials used to make it, especially given the extra mass of water for solutions, on a small scale it should cost you less to buy the finished product than the methanol or formaldehyde and ammonia.

So the easy way to hexamine is to buy. And yes, SFAIK the only practical route is via ammonia and formaldehyde.
Sauron
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Just my advice, son, but unless you are fond of the rotan I would not get caught in Singapore making or acquiring the basic raw material for preparation of RDX and HMX.

I would be very surprised if its sale and manufacture are not proscribed without a special license in Singapore.

Naturally you could try to convince the authorities that you needed hexamine aka hexamethylenetetramine aka Urotropine as a urinary tract disinfectant. Good luck with that defense.

The tedious part about the prep of hexamine is that both formaldehyde and ammonia are employed in their aqueous solutions and all that water needs to then be evaporated off after the condensation of 6 mols formaldehyde and four mols ammonia. As if you didn't have enough water to get rid of, the condensation itself produces more water.

My advice is, stick to a peper chase on energetic materials or move to a freer country. In Sg, even a paper chase can land you in hot water these days.

As a former highly paid consultant to Singapore's MOD, I am familiar with their methods. Changi is a nice airport but a nasty prison.
Rosco Bodine
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Actually paraformaldehyde mildewcide and strong ammonium hydroxide blueprint developer spontaneously combine to form hexamine very easily . Any alkali depolymerizes para very easily , which the ammonia does , and then further reacts in the usual way known to those who are skilled in the art
tito-o-mac
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Alright I give up. I guess my country is too sensitive to the slightest movement. "urinary tract disinfectant" doesn't seem like a good excuse. You could even get caught for purchasing over 2 kg of sparklers

Sauron where do you formerly work? How do you obtain your chemicals?

[Edited on 20-7-2007 by tito-o-mac]

[Edited on 20-7-2007 by tito-o-mac]
Bromide
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Fuel tablets?

 Quote: Originally posted by tito-o-mac Alright I give up. I guess my country is too sensitive to the slightest movement. "urinary tract disinfectant" doesn't seem like a good excuse. You could even get caught for purchasing over 2 kg of sparklers Sauron where do you formerly work? [Edited on 20-7-2007 by tito-o-mac]

I realize Singapore is an extensively developed parcel of real estate, but you mentioned previously that you reside "in the boonies" so to speak--which leads one to a reasonable assumption that there are at least some natural areas to be enjoyed.

So, does anyone in Singapore ever go camping? Are there boy scouts who sleep out in tents overnight, etc.? Then you may well find a ready-made source of hexamine in the form of dry fuel tablets of the kind used in camping stoves. The brand I am familiar with, Esbit, is a German company that has been marketing hexamine fuel tablets for the past 70 years (see, for example, http://www.esbit.de/www/index.php?id=67 ). Perhaps make a few calls to outdoors stores or the like, and see if they carry fuel tablets.

The hexamine in fuel tablets would still require extraction from the binders and excipients that are mixed in to provide rigidity and form to the tablets, but it shouldn't be more difficult than trying to synthesize hexamine from raw precursors. G'luck.
PHILOU Zrealone
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It is not uneconomical.
It is simply the physical limit of concentration of formaldehyde (methanal) and of ammonia in water that are the problem.

Wel is it really a problem?
Taking in account that otherwise you would have to handle gases wich are toxic and highly reactive towards membranes (skin, eyes, nose, mouth, ...), taking in account the fact two gases reacting to make a solid would result in the loss of 5 levels of freedom (on the molecular level) and thus result in extensive heat (exotherm)...
So water makes it relatively safe to make, takes the heat and is easily removed on standing in air under the sun.

Hexamine has also the ability of being sublimable at hight temperature without decomposition so boiling is also a good way. There is maybe a retroactivity to methenimin (CH2=NH) during the warming that would account for this fact.

Commercial concentrated ammonia is 12-30% by weight and formol 30-40%.
So you have to take rid of the 88-70% water and 60-70% water from teh reactants and also from the condensation water wich is formed during the process.
CH2=O + NH3 --> CH2=NH + H2O

[Edited on 19-7-2007 by PHILOU Zrealone]

PH Z (PHILOU Zrealone)

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Sauron
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I was for four years during the 1980s, the US agent for two MOD owned Sg companies, Unicorn Intl and Chartered Firearms Industries, part of the Chartered Industries of Singapore complex under Army security control in Jurong Town. Behind CIS was an ostensibly private company actually MOD controlled called Sheng Li Holdings. As you doubtless know Sheng Li means Victory. In the late 80s all this was reorganized into the still extant Singapore Technologies Corp. The main govt technocrat in charge was Philip Yeo. My position was arranged by William Colby who was advisor to Lee Kuan Yew, I suspect you know who he is. Colby you may not have heard of as he died during the Clinton years but he was Director of Central Intelligence in US during the early 1970s.

I have lived in Thailand since a few years after my relationship with Sg's government ended. While I am essentially retired,
I now have a registered corporation in BAngkok and buy my chemicals quite openly from major suppliers like Merck, Acros, Aldrich, Fluka AG, Alfa, etc. via their local agents. The powers that be in Thailand know who I am and what I do. I luncheon regularly with the retired chief of Royal Thai Army Intelligence and the Special Warfare Command. It is very nice to have good friends.

I am not discouraging you from inquiry, just recommending that you not do anything foolish in these troubled times in Sg where whether you know it or not, they do have legitimate security concerns behind those draconian public security laws dating from the colonial period and the Emergency across the Johore Straits. Look what is going on in Indonesia, Malaysia and southern Thailand. You really don't want to be misunderstood and miscategorized at a time like this.
tito-o-mac
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One more important thing: it's carcinogenic!

[Edited on 20-7-2007 by tito-o-mac]
Sauron
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What? Formaldehyde? No it is not carcinogenic. It was suspected for a while but finally they decided there was no evidence so they delisted it as "reasonablt ancicipated to be..."

There is still only a very short list of proven human carcinogens.

These include ketene, benzidine, bis(chloromethyl) ether, benzene, b-napthylamine, and so on. For the full list see Org.Syn. This list has changed little. A lot of proven human carcinogens came to light in the dye industry.

Many many others are SUSPECTED human carcinogens, they may be suspected because they are known mutagens, or known animal carcinogens, and so by extrapolation, suspects.

sparkgap
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"Are there boy scouts who sleep out in tents overnight, etc.? Then you may well find a ready-made source of hexamine in the form of dry fuel tablets of the kind used in camping stoves."

As it stands, there are two kinds of stove fuel tabs available in Asia. One, as was said, is composed of hexamine. The other one is made up of trioxane.

You'd think it'd be tough luck if all you can find is trioxane.

That is, unless you remember that this, like paraformaldehyde, can be decomposed to formaldehyde.

Sometimes also, you'd encounter fuels that are a mix of hexamine and trioxane.

'course, if neither of these are available, you might want to hang around the nearest mortuary... :p

sparky (~_~)

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Aqua_Fortis_100%
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some years ago i've made (assuming that is really hexamine ) hexamine from aqueous CH2O , ammonium sulphate , and Ca(OH)2..

IIRC , ammonium suphate react , in equilibrium, with formaldehyde , to form hexamine and H2SO4..but unfortunately (well, at least in this case) will tend to decompose back in CH2O and NH3 in acidic solutions.. so added slowly added Ca(OH)2 (lots of heat generated) , filtrated the most CaSO4 (not_important said to me a time ago that calcium salts are more soluble in NH4+ compounds..so , today that i've made was the dirty and shitty thing..but was more for fun ,than acquiring large amounts of HMTA)..

the evaporation of this, have left on the enameled pan a yellowish moist mass, which on further heating to get rid off the water, decomposed part of this on a black residue (non caught H2SO4 ??) very quickly... so i just throwned all things on the basket without furt "analysis".. Can anyone say if this is possible?? have anyone tried isolate the product or if is reliable to a "alternative method"??(my deals in that time was the minimum handling of water evaporation, without using somewhat fancy chemicals, like p-formaldehyde and such..the large excess of water in solution up set me..is a mess , costs lots of energy(assuming that i use a kitchen gas stove) and yield little amount (although is much more pure)...furthermore, can it be an alternative, using an salt (eg (NH4)2SO4) as opposite of strong ammoniacal solutions (hard to find here)??)

[Edited on 30-7-2007 by Aqua_Fortis_100%]

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tito-o-mac
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Ha ha, after months of chasing stores, my ahrd work paid off! I manage to get my hands on some hexamine(not a big deal actually)!!! P.S. It's ordinary in other countries, but rare here

[Edited on 22-8-2007 by tito-o-mac]

Sauron
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So now that you have your mexamethylene tetramine what are you going to do?

It is useful in certain formylations.

You may need to purify it as it may have been compounded in the tabletizing process with binders and the like.
tito-o-mac
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Can you name a list of formylations then? Also, is there method of purifying hexamine?
YT2095
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ok, NOW Im confused!?????

you went to All this effort and others here put in effort for you, now you HAVE the Hexamine, you dont know what you wanted it for?????

WTF?

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Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
Zinc
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Hexamine

I made hexamine solution by mixing around 30 ml of 25% ammonia solution and 60 ml of 36% formaldehyde solution. When I mixed the solutions they got hot to the touch. After a few minutes it cooled. Now can I boil down the solution to get hexamine or must I leave it to naturally evaporate?

joeflsts
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 Quote: Originally posted by Zinc I made hexamine solution by mixing around 30 ml of 25% ammonia solution and 60 ml of 36% formaldehyde solution. When I mixed the solutions they got hot to the touch. After a few minutes it cooled. Now can I boil down the solution to get hexamine or must I leave it to naturally evaporate?

I kept it on an ice bath for 24 hours after the reaction had completed and then evaporated the water to dryness. I then collected the wet hexamine and heated until the water was completely driven off.

Joe
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I made mine also keeping in a ice bath(when large volumes of reagents are mixed) and after one day I boil solution (ammonia smell starts.. and after a few mins a smell of formaldehyde.. So I keep ading some ammonia while evaporating solution to dryness

(Some Years ago , because of ammonia which is hard to find in good concentrations I tried to dissolve farmers grade ammonium sulfate in formaldehyde and driving the reaction with excess of Ca(OH)2 .. The addition of lime was slow (and with stirring) because of the heating that was great..After I filtered the CaSO4 I tried to evaporate in a iron pan and a yellowish mass formed.. When the mass was almost completely dried the thing started to char !!! I don't know what caused this, but I think that some sulfuric wasn't neutralised, even with excess Ca(OH)2.. what about?)
So I abandoned this 'method' and back to expensive (for me), but much cleaner, formaldehyde/ammonia method..

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Zinc
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 Quote: Originally posted by joeflsts I then collected the wet hexamine and heated until the water was completely driven off. Joe

Did you heat it in a oven? At what temperature and for how long?

joeflsts
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Quote:
Originally posted by Zinc
 Quote: Originally posted by joeflsts I then collected the wet hexamine and heated until the water was completely driven off. Joe

Did you heat it in a oven? At what temperature and for how long?

Yes, I place it into a crucible and heated in the oven for about an hour @ 300F until it fused.

I have been storing it about 5 months and it is still fresh.

[Edited on 6-1-2008 by joeflsts]
Aqua_Fortis_100%
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Mine is also perfectly fresh and dry.. And I've used a stainless steel pan on the stove without problems.. But I used the weakest fire and was very watchful stirring and (re)placing the pan on fire every moment to avoid overheat...the worst part is when it forms a 'paste', bacause if you heat too much the mass will 'bump' and 'fly' all around you

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franklyn
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A possible alternative synthesis _
Heating Dichloromethane with alcoholic ammonia at 100-125°C results in hexamethylenetetramine

Search the Kirk Othmer Encyclopedia of Chemical Technology CD for ( Methylene Chloride )
select the [ article-titles ] filter , scroll down past the tables of properties, the quotation is above
the heading for Manufacture , between citations ( 8 ) and ( 9 )

Hardware store bought paint stripper is a blend of Methylene chloride and Methyl alcohol
around \$ 35 gallon , this then only need be gased with ammonia which is somewhat soluble
perhaps ~ 10 %.
I have never been able to find any other references to this and really wonder about the
overall yield, not to mention the safety of boiling this under pressure.

.
Zinc
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 Quote: Originally posted by joeflsts I kept it on an ice bath for 24 hours after the reaction had completed

Does it have to stand for one day or can I evaporate the solution sooner?

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