Sciencemadness Discussion Board

Hydrazine Safety & Handling Questions

Sauron - 14-11-2007 at 17:26

This is directed at those who have a lot more practical experience with working with hydrazine hydrate than I do.

I have some preps I wish to do that call for this compound.

The only local stock of hydrazine hydrate is Carlo Erba 98% one liter in plastic bottles. Otherwise I have to ship it in which entails waiting a couple of months.

The procedures call for 42% so I figured I would dilute the 98% and be done with it.

My questions are:

Any general advice? I know it's probably carcinogenic. I certainly will not be distilling it. It'll only get used in the hood.

Some of the procedures suggest that rather than using the hydrate, employ hydrazine sulfate and NaOH to make the hydrate in situ. Others make no mention of this. Is this quite general?

The reactions I want to perform are:

Preparation of aminoguanidine from S-methylisothiourea and hydrazine hydrate

Preparation of 1-guanyl-3,5-dimethylpyrazole from aminoguanidine and hydrazine hydrate.

Reading about hydrazine hydrate, it is stated that relatively dilute solutions are safer than the 100% hydrate. I know that the max.hydrazine content is 64% so this 98% solution as supplied is c.63% hydrazine and the 42% solution is 26-27% hydrazine. (In case anyone does not know, work out the MWs of hydrazine and water when considering the monohydrate.)

Fleaker - 14-11-2007 at 19:46

Just do not touch it or allow contact with skin. The hydrazinium hydrochloride I use for Pt precip states in bold letters: "DANGER: known carcinogen". Also, if concentrated, it is very imperative that you avoid ANY oxidizers whatsoever.
You could possibly make the hydrazine sulfate (cheap, but probably a day long proposition) and then do it in situ, but I do not know how that would affect your reactions.

Rosco Bodine - 16-11-2007 at 21:52


If the price for the hydrazine hydrate is unreasonable ,
as it can sometimes be ,

Hydrazine sulfate is easy if you can get some 10% bleach and urea .

If you are experimenting with a synthesis of aminoguanidine as your intermediate , I wish you would investigate the possible reaction of hydrazine sulfate and any guanidine salt . There reportedly is a way of making the diamino and triaminoguanidines this way depending upon the ratio of number of moles hydrazine available for reaction per mole of guanidine salt , and I believe the monoaminoguanidine forms as the first intermediate in that reaction scheme .

IIRC the synthesis is analogous to the formation of nitroaminoguanidine from nitroguanidine and hydrazine sulfate , neutralized with ammonia to provide nascent hydrazine in the reaction . But instead of reacting nitroguanidine to form nitroaminoguanidine , a non-nitro
ordinary guanidine salt like the hydrochloride perhaps
should lead to aminoguandine via the same scheme .

Gassing the completed reaction mixture with CO2 or perhaps using sodium bicarbonate and possibly neutralizing with HCl or acetic acid ect. should precipitate
the aminoguanidine as the nearly insoluble bicarbonate .

This may be a novel method if it works as I am thinking it will .

See US5041661

The yield however for the above reaction is lower than for the more efficient reaction with calcium cyanamide which is patented by Bayer . (attached) The economics for the Bayer process are probably the best of the chemical methods .

And of course the hydrazine requirement can be eliminated if desired , by the alternative route involving chemical or electrolytic reduction of nitroguanidine .

That would still leave you with the hydrazine requirement for your further reaction contemplated for the aminoguanidine , unless there is an alternative there also .

[Edited on 17-11-2007 by Rosco Bodine]

Attachment: GB1218209 Aminoguanidine Bicarbonate via Calcium Cyanamide and Hydrazine Sulfate.pdf (503kB)
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Boomer - 19-11-2007 at 09:56

Never worked with hydrazine (Astrolite being one of the few HEs I had no desire to mess with), but from memory : Nitroguanidine from guanidine nitrate, this made by fusing AN with dicyanodiamide, which can be made from fertiliser (lime nitrogen) .... Extremely easy but also extremely tedious. If you like working with multiy-gallons, big buckets and lots of parallel filters - it may be your thing.

But wait, can't you buy aminoguanidine bicarbonate where you live?
I did all that cooking and filtering to prove NQ could be done OTC, and when I say OTC I mean taking a walk with a shopping bag. Your time will be too limited for this route.

YT2095 - 19-11-2007 at 10:14

and for what it`s worth, I seem to remember reading somewhere that it`s quite nasty even in small amounts by Inhalation, resulting in headaches that can last for weeks and the likes.

certainly a Handling precaution that`s not to be Sniffed at :P

(Pun Intended)

[Edited on 19-11-2007 by YT2095]

Sauron - 19-11-2007 at 16:23

Astrolite I believe employs anhydrous hydrazine as one of its components, and anhydrous hydrazine itself is self-explosive.

I am not working with anhydrous hydrazine. Only rather dilute hydrazine hydrate. 100% hydrazine hydrate is by definition 64% hydrazine 36% water.

I am not preparing aminoguanidine from nitroguanidine reduction. I am preparing it from S-methylisothiourea and hydrazine hydrate. Yes, I could just buy the aminoguanidine, but it is rather expensive. I'd rather make it. The S-methylisothiourea is cheap and commercially available; so I will not bother to make it from thiourea and dimethyl sulfate though I have both at hand (nasty stuff.)

I bought a Kg of guanidinium carbonate as an alternate feedstock and so I will be able to try out Rosco's route with hydrazine sulfate (to aminoguanidine.)

The point of all this is to condense aminoguanidine with acetylacetone to make 1-guanyldimethyla pyrazole, which is a guanidating reagent for amines.

Something I ran across while searching amino acid preps for one of the members. Though his application (making arginine from ornithine) is clearly uneconomical, ornithing being twice as valuable as arginine.

Rosco Bodine - 20-11-2007 at 16:40

Actually the route for aminoguanidine from nitroguanidine reduction is higher yield , nearly twice the possible yield based on the original guanidine salt . And that reduction method requires no hydrazine of any form . So the economics are are unbeatable for the reduction route .

Alternately the patent suggested method I was contemplating using a guanidine salt and hydrazine has a maximum yield of 50% if it follows the same path as the reaction producing the nitroaminoguanidine from nitroguanidine , because an intermediate addition compound may likewise be formed , a complex which
then decomposes to two different products , only one of which is the desired aminoguanidine . The interest here
then is simply convenience for the situation where common reagents like guanidine hydrochloride and hydrazine sulfate may be on hand . It also provides a
possibility for diamino and triamino guanidines if a corresponding excess of hydrazine is provided for the reaction .

If you are going to synthesize aminoguanidine via a hydrazine reaction route , the economics favor the
calcium cyanamide reaction which is a straight shot single route involving no lossy intermediate complex . And hydrazine sulfate may be used as the hydrazine source . Also if you have a kiln or even a low red heat range burnout furnace , pure calcium cyanamide may be conveniently made by pyrolytic decomposition of calcium cyanurate , easily made from CaCl2 and cyanuric acid dihydrate pool chlorine stabilizer . This pyrolysis might even be done in a covered crucible on a clay triangle over a meker burner , fired to a soft red heat for a few minutes , for small quantities . I'm not sure as I haven't tried it . My last ashing crucible cracked when I was melting some scrap silver and I don't have one handy to try it . But all it takes is a low red heat and avoidance of excess exposure to air .

Attached is a later patent that is a variation of the Bayer process . Evidently the antioxidant properties of aminoguanidine are useful as a stabilizer for petroleum based fuels and lubricants , so the oil companies as well as the pharmaceutical manufacturers have had an interest in aminoguanidine , aside of course from the interest of others in regards to the energetic derivatives .

[Edited on 20-11-2007 by Rosco Bodine]

Attachment: US4906778 Aminoguanidine Bicarbonate.pdf (270kB)
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Sauron - 21-11-2007 at 08:49

I have opted to proceed from commercially available, and inexpensive, S-methylisothiourea, and hydrazine hydrate. The lit. reference for this one-step, 90% yield preparation of aminoguanidine, taken from JACS, is attached.

The classical prep sequence of guanidine nitrate to nitroguanidine to aminoguanidine is very well known. However the cautions at start of the Org.Syn. prep of guanidine nitrate are worthy of the attention of anyone interested.

[Edited on 21-11-2007 by Sauron]

Attachment: f_ja01315a510.pdf (102kB)
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