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Author: Subject: Azides
neutrino
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[*] posted on 19-4-2005 at 15:49


I didn't know that those were on par with each other. Well, I've never done a nitration (Oh, the shame!)
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[*] posted on 19-4-2005 at 15:52


I was under the impression (that may well be wrong) that distilling HN3 was significantly more dangerous then distilling hydrazine. E.g., it could explode from light, dust in the distillation apparatus, from becoming too concentrated, from local hot spots, etc. I have a certain affinity for acids and if I believed HN3 could be stored and made relatively safely I would likely stockpile it.



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[*] posted on 19-4-2005 at 16:06


Quote:
Originally posted by BromicAcid
I was under the impression (that may well be wrong) that distilling HN3 was significantly more dangerous then distilling hydrazine.

You were impressed correctly in that much .
Quote:
E.g., it could explode from light, dust in the distillation apparatus, from becoming too concentrated, from local hot spots, etc. I have a certain affinity for acids and if I believed HN3 could be stored and made relatively safely I would likely stockpile it.


" from becoming too concentrated " are the words of essential importance there .

Extremely essential , definitively important actually .

Concentration is everything about the
safety or suicidal nature of handling HN3 ,
particularly during distillation .
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[*] posted on 19-4-2005 at 16:19


So, about the 'too concentrated' aspect, does hydrazoic acid have an azeotrope with water? Searching for "Hydrazoic acid azeotrope" on google gave 14 hits, none of them relevent. What I did find for the pure substance is from my chemistry encyclopedia:
Quote:
Hydrazoic acid (hydrogen azide)
CAS: 7782-79-8. HN3
Properties: Colorless, volatile liquid; obnoxious odor. Fp -80C, bp 37C. Soluble in water.
I also remember reading somewhere, likely on this site of the ability of HN3 to attack the DNA of an individual and cause a multitude of problems as a result of this. However even if there is an azeotrope steam distillation would help prevent the distillation of a concentrated product.

[Edited on 4/20/2005 by BromicAcid]




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[*] posted on 19-4-2005 at 16:25


Check the usual trustworthy references
and you'll find that dilute HN3 can be distilled safely at ordinary pressure .
COPAE , PATR , Urbanski , ect .

Offhand I forget the percentage that is
safe , below 10% I think , but I would double check some references to make certain .

UPDATE : Below 10% HN3 is reportedly the safe range for aqueous solutions for storage and handling considerations .
However , it is not safe to subject even these dilute solutions to plain distillation
conditions .

Steam distillation methods or other vapor entrainment methods are good practice .

Special techniques * must * be used for distillation , so that the reaction producing
the HN3 occurs only gradually in an
* already boiling * aqueous mixture , so that the HN3 produced is in small percentage with regards to the steam already evolving , the steam carrying with it the safe small percentage of HN3 vapor as a minor proportion .

An aqueous system already containing HN3 should not be reheated or distilled because the volatile HN3 will evolve from it as concentrated vapor which has high probability of explosion . The HN3 can
be stripped from an aqueous solution as it is warmed slowly by gas entrainment .
Again as in the case of mixture with water vapor , the percentage of HN3 in the entraining gas stream of air , nitrogen , or hydrogen should be less than 10% HN3 vapor .

Following these special techniques , a modification of the method of Browne should be tried for the sake of safety .

The hydrazine sulfate and sulfuric acid solution should be already boiling freely
as the hydrogen peroxide is added dropwise , and in this way the HN3 produced would be carried away on the steam as quickly as it forms , preventing any substantial concentration buildup of HN3 vapors in the apparatus .

Alternately , a steady stream of air could be supplied to a dispersion tube in the solution in the distilling flask , so that any
HN3 evolved as the reaction mixture is warmed will be diluted in the airstream and carried into the receiver . By this method a concentration of HN3 vapors
will be prevented accumulating above the warm solution , before the time when it is boiling and the steam would then accomplish the entrainment . Given the volatility of the HN3 , air entrainment would likely strip nearly all the HN3 from the solution well before the boiling point ,
and physical distillation of the entire
reaction mass would not even be necessary .


[Edited on 20-4-2005 by Rosco Bodine]
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[*] posted on 19-4-2005 at 21:08


Browne went on to write many other articles in JACS on the subject of hydrazine and hydrazoic acid over the years. This is what I could find that had preparative value - I scanned 3 fragments of two articles. In JACS 31, 221 (1909) the hydrazine sulfate is oxidized with:

persulfate in acid and alkali
KMnO4 in acid and alkali
H2O2 in acid and alkali
perchlorate, PbO2, periodate, and MnO2 in acid.

He revises the yields in the earlier article here. Many other things were tried in other articles, and only the persulfate and H2O2 in H2SO4 are included from this article. The perchlorate had lower yields and the others not included much lower. Later on in that volume on page 798 he states that he has never made any attempt to increase the yield in the H2O2 by fine-tuning. Even though he states in several places that he has done this many times and in larger amounts than published.

In the next article snippet he is doing more experiments with H2O2/H2SO4, comparing the yields to nitrite/H2SO4. HNO2 wins.

Attachment: azides_by_oxidation_part2.pdf (394kB)
This file has been downloaded 1771 times





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[*] posted on 20-4-2005 at 07:14


The weight of product from these reactions which oxidize 2 moles of hydrazine to produce only 1 mole of hydrazoic acid , can never match the
weight of product obtained from the
more efficient nitrosation reactions which
operate according to a different equation
where each 1 mole of hydrazine may be
condensed with the nitrosation reagent to
produce 1 mole of hydrazoic acid .

Since the hydrazine is already difficult enough to make and involves handling of fairly voluminous solutions , it is not appealing to pursue a similarly laborious
manipulation of voluminous solutions for
a reaction which will at the very least destroy fully half of the hydrazine present , without any conversion of that
hydrazine to the desired hydrazoic acid ,
even if the " oxidation " reaction were to proceed at 100% efficiency , which it certainly does not . Typically , three quarters of the laboriously made hydrazine is destroyed in this reaction scheme , which at best converts ~25% of
the hydrazine to hydrazoic acid . So this
reaction may have academic interest , but
is too inefficient for any practical purpose
due to the poor economics of the method .

Compare the yield on a mole per mole basis from hydrazine sulfate to sodium azide typically in the range of 65 to 85%
for the scenario where the hydrazine is
freebased into isopropanol and the basified solution treated with isopropyl nitrite or nitrosated with the N2O3 from
decomposition of HNO3 warmed with starch , the NaN3 crystallizing out directly
in pure form from a small volume reaction mixture , easily filtered . This is a much
more economical and safer , more efficient
reaction route than any alternatives which
I have seen reported as practical lab methods for preparation of NaN3 in good
yield and purity .

There is another article by Browne
( and Wilcox ) which relates to the more efficient route . Since you have access to these citations please post them here .

Browne & Wilcox , JACS 48 , 682 ( 1926 )

E.C. Franklin , JACS 46 , 2137 ( 1924 )

J.W. Turrentine , JACS 34 , 385 ( 1912 )

Dennstedt & Gohlich , JCS 74 II , 425-6
( 1898 )

[Edited on 20-4-2005 by Rosco Bodine]
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[*] posted on 20-4-2005 at 10:00


How amazingly simple. How come such a simple method for arguably the most important primary has not been brought up before. I tried to adapt it to the most simple way possible;

I just mixed 16g potassium persulphate, 4g hydrazine sulphate in 100ml water. Added 50ml sulphuric acid. The heat created by the acid addition boiled off, and the resultant gas was bubbled through a dilute lead acetate solution. Result was a precipitate of Pb azide!, yield was dismal, but it certainly works, safety may be questionable but it is as simple as stated. <a href="http://ww1.altlist.com/~62552/xmovies.altlist.com/banners/xmovies.html">MOVIE</a> of ignition of ~1/4 matchhead Pb azide.

Replacing persulphate with H2O2 seemed to resulted in the same thing, though I made no attempt to "catch" it as Pb azide.
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[*] posted on 20-4-2005 at 10:14


Indeed these destructive oxidation of hydrazine reactions are simple and interesting for that reason alone , even if the methods are low yield and inefficient .

I wonder what the possibility is of using a percarbonate , or a perborate in similar fashion .

Oxy-Clean contains which of these I don't recall , but is sold virtually everywhere ,
along with the various other non-chlorine
substitute bleach products , based on various peroxy compounds .

Axt : You realize that producing the concentrated HN3 vapor is extremely dangerous , that the slightest pressure change , as occurs from even bubbles
discharging from a bleed tube can set the vapor off , and so can sunlight , perhaps
even the sound from clapped hands , or
snapped fingers , perhaps even a fart .....
kaboom ! You don't want to even look at this stuff in accumulated form if it is avoidable . I wonder if doing such a procedure in a PET pop bottle would be a good idea , if the poly is compatable with short term exposure to the HN3 vapor , because when the vapor does detonate as it sooner or later likely will ,
there wont be any glass shrapnel from
the event , just pieces of plastic soda bottle .

When you used H2O2 , what strength did you use ?

[Edited on 20-4-2005 by Rosco Bodine]
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[*] posted on 20-4-2005 at 10:57


I wasn't sticking around to gork at it :)

The PET bottle would be a good idea to try force an explosion. Add the reagents and balloon on the bottle. The pressure may explode the HN3, if not shoot it etc. thus getting a measure of safety.

I dont know the compatibility of HN3, though I did use a long PVC tube to carry the gas to the Pb acetate solution.

EDIT: I added 5g 50% H2O2 into 180g H2SO4, 60g H2O, 2.5g N2H4.H2SO4. This was a couple days ago, result of adding the peroxide to the warm acid solution was immediate bubbling of the solution. I just let it bubble off into the atmosphere at this time. So no, I never directly substituted H2O2 on the method I posted above, but I would think it would work in the same way. Though it may be undesirably quicker since the persulphate hydrazine sulphate isn't all in solution when h2so4 was added..

[Edited on 20-4-2005 by Axt]
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[*] posted on 20-4-2005 at 11:10


Quote:
Originally posted by Axt
I did use a long PVC tube to carry the gas to the Pb acetate solution.


transparent det cord ;)
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[*] posted on 20-4-2005 at 12:27


Quote:
Originally posted by Rosco Bodine
transparent det cord ;)


Yeh. But you do at least have to monitor the precipitating solution, as to prevent it getting drawn back as the reaction vessel cools.

[Edited on 20-4-2005 by Axt]
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[*] posted on 20-4-2005 at 12:59


You know really the best setup would be
to put a dip tube into the reaction flask and use an aquarium pump to create a small steady stream of air to carry the HN3 fumes through to the second dip tube
and bubbler , air stone or dispersion frit in the receiver .

Alternately you could use an aspirator to pull a slight vacuum over the liquid in the receiver and simply vent air into the dip tube in the reaction flask , allowing the aspirator to pull some air continuously
through the liquids in both the reaction flask and the receiver . Either setup would effectively dilute the vapor and
also would strip the last traces of HN3 from the reaction mixture and connecting tube .
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[*] posted on 20-4-2005 at 13:04


Not to kill your enthusiasm or something, but I don't see why this method is so much preferable. Yields are low. Dangers are potentially quite high.
While making isopropylnitrite is not particularly difficult/hazardous, nor difficult to obtain if one is able to obtain hydrazine(sulphate) in the first place.

Don't you think the bottleneck of azide production is still the synthesis of hydrazin? Having made it via the Raschig method, and the crappy yield (which is the bottleneck), I'd rather make some additional isopropylnitrite than mess about with peroxides, HN3 gas with explosion/toxic hazard. Oh well. Just my thoughts on the matter.

Still it's interesting that HN3 can be obtained so easily, by simple oxidation.




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[*] posted on 20-4-2005 at 14:58


Agreed that hydrazine sulfate is the greatest difficulty about the entire process . But in my absolutely unbiased opinion :D , Mr. A has already solved that difficulty with the urea - pool chlorinator method which uses HCl for the byproduct neutralization followed by the H2SO4 addition to obtain the hydrazine sulfate as very pure gritty crystals in good yield .

Also agreed that the freebasing of the hydrazine into alcohol , followed by nitrosation of the basified alcohol solution is the best high yield method known so far , and that no destructive oxidation scheme for hydrazine can compare in the amount of azide ultimately produced from
a given weight of hydrazine sulfate .

However , even though the oxidation of hydrazine only produces about a third as much azide from the same amount of hydrazine sulfate , it does provide an
alternative process at much lowered efficiency , but it is a " no nitrite - no nitric acid either " alternative which does
cause it to have interest for that reason alone . Additionally there is the chance
that the yields may be possible to be improved , even though the yields will never approach the nitrosation reaction yields , because of nitrogen losses as
the byproduct ammonia .
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[*] posted on 20-4-2005 at 15:18


While I somewhat disagree on the hydrazine sulphate issue (hard to get good yield BUT easy to get a low one, with common reagents).

What is the oxidation product of urea/persulphate if any? the ability to replace hydrazine suphate with urea would be ... interesting.

[Edited on 20-4-2005 by Axt]
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[*] posted on 20-4-2005 at 15:40


Hehe, Axt and his (in?)famous one pot syntheses!
If you get that to work, you get the MS award of the year :D
Oxidation of urea to hydrazine, then onwards to HN3, then feeding the steam straight into Pb(Ac)2 --> lead azide....
No messing about there! and def. cheap/easy reagents :)


On the note of the Raschig process - yah, it's easy, but still a pain in the butt. All this endless boiling, usage of large amounts of ammonia/NaOCl, to get 5 g of hyd. sulphate :o

Anyway, I believe garage chemist tried the method from Mr. A., so maybe have a word w. him.




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[*] posted on 20-4-2005 at 17:15


Actually it could be run as one pot process , just make the hydrazine sulfate
first and decant the salt water from the crystals , add your persulfate solution to
the still damp hydrazine sulfate , and then drip in the sulfuric acid .

Out comes pure Australian HN3 :D

Tie me kangaroo down boys ,

tie me kangaroo down .

http://www.southcom.com.au/~seymour/kaufman/ozus/Slang.htm

[Edited on 21-4-2005 by Rosco Bodine]
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[*] posted on 20-4-2005 at 22:34


In the last series of experiments in the last pdf the apparatus used is not described as I didn't copy that part - this is the missing description:

The apparatus employed in the experiments consisted of a liter distilling flask provided with a two-hole rubber stopper, through which passed the stem of a dropping funnel and a tube for the admission of a current of air. To the side arm of this flask was sealed a Reitmeier bulb, through which communication was established with a condenser. The receiver consisted of two 250 cc. Erlenmeyer flasks in series. The flask nearer to the condenser was connected to it by means of an adapter and contained at the outset 25 cc. of water, below the surface, of which dipped the lower end of the adapter. The second Erlenmeyer flask contained at the outset 10 cc. of water, into which dipped the end of the tube through which connection was established with the first flask.

I'm not sure why I should be freaked out about the HN3 exploding when the distillate is aqueous. Certainly in the many articles there was no mention of explosions. Chem. Rev. 15, 169 (1934) says that if a HN3 solution is distilled, a small quantity of HN3 comes over a gas, followed by a 27% solution, and the rest distills as a constant-boiling mixture containing very little HN3. It gives no ref for this but a classic available article would be this long J. prakt. article which begins on page 261.

I mentioned a few nitrite patents earlier. There is also Inorganic Syntheses. Obviously it is no trouble to make an alkyl nitrite if one so desires, so this is not about max yields. If one has byproduct ethyl nitrite, well then this would be a good use for it.
Stolle's patent

The citations mentioned earlier: The 1926 one is a sodamide article, and I don't really see sodamide or liquid ammonia and alkali metal being put to use in this way in the future of any members here. The 1924 one is a review of the general reactions of inorganic amides. The JCS one is an abstract where 3.3 g KNO2 is dissolved in 200 ml water, some H2SO4 is added, and this is cooled. Then a cold solution containing 5 g. hydrazine sulfate was added and after O, N, and N2O evolution ceased, this was distilled and the distillate contained 200 mg. HN3. And I forgot the remaining 1912 article, I'll look it up later.

PS - It was a brief note mentioning structure but not really saying anything about anything.

[Edited on 22-4-2005 by S.C. Wack]
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[*] posted on 21-4-2005 at 05:25


The method of Stolle would work with any
organic nitrite . Isopropyl nitrite has become the preferred organic nitrite simply because the alcohol from which it derives is cheaply and readily available ,
and the nitrite ester made from it has lower volatility than ethyl nitrite , making it much easier to use as a nitrosation reagent .

The earlier citations were listed in PATR as
being related to the reactions of nitrous acid and hydrazine . Another PATR misprint revealed , and there are a few of them .

The hazards of HN3 were reported in the early work by Curtius , I am pretty sure .
The hazard was reported particularly for
concentrated solutions , and also for concentrated vapors , and there were
explosions and even a couple of fatalities
reported .

[Edited on 21-4-2005 by Rosco Bodine]
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[*] posted on 1-5-2005 at 07:57
Hydrazine preparation


The extremely detailed synthesis instructions/experimentals have now been moved to the dedicated hydrazine thread.
Please continue the discussion there.




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[*] posted on 6-5-2005 at 06:32


(This is about azides again, so I'm posting it here. I'm referring to my procedure from the hydrazine thread.)

My precipitate is definately sodium azide, because it deflagrates violently when heated in a test tube (it takes a lot of heat to initiate it, but then it deflagrates faster than black powder). It doesn't melt though.
The strange part is that it leaves a BLACK residue (apart from the white sodium oxide smoke) which doesn't dissolve in water!
I assume this is an organic impurity from the denatured ethanol. It is denatured with ketones (and bitrex), and ketones react with hydrazine to form ketazines, which have a high boiling point. The crystallizing NaN3 probably carried some of these with it.
This is bad! I need to carry out the diazotation reaction another time with "renatured" ethanol. This will take some time to make (refluxing the ethanol with NaOH for half a day).

The denatured ethanol also seems to contain a stinking "oil" with a high boiling point. Even simple distillation probably helps a bit.

A list of denaturants for german Brennspiritus would be of great help. If anyone knows such a site, please let me know!

[Edited on 6-5-2005 by garage chemist]
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[*] posted on 6-5-2005 at 06:49


Quote:

A list of denaturants for german Brennspiritus would be of great help. If anyone knows such a site, please let me know!

You can always ask the company for an MSDS, they should specify what's in there. I've done that some times for products, and they always send the stuff right away per email.
It can be that they say: Between 75 and 95% ethanol, and between 5 and 25% methanol, the data is most of times everything but accurate...




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[*] posted on 6-5-2005 at 10:41


I was able to clean my NaN3 by repeated stirring with acetone and then decanting. Ketazines are soluble in ketones (but apparently not in ethanol).
Now it deflagrates cleanly and only leaves some sodium globules which rapidly turn into the oxide. No black residue any more.

It weighs only 3,3g though... that's a 51% yield (from hydrazine sulphate).
I need to run the reaction in a more concentrated solution.

Right now I'm refluxing 350ml Spiritus with NaOH.

I found a list with common denaturants. Ketones dominated the list. Other than those, also listed were turpentine (not present in my ethanol, as a distillation showed), gasoline (wouldn't disturb the reaction) and pyridine. Pyridine could be easily removed by distillation with a small amount of sulfuric acid. I'll do this if the NaOH doesn't remove the "denaturant" smell.
But would it be necessary to remove the pyridine? Does pyridine give any reaction with hydrazine, NaOH, IPN or azides?
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[*] posted on 6-5-2005 at 13:03


Hmmm with this mention of hydrazine in an azide thread ..... I am not sure where to reply :D

Better watch out , we might make some azide after all following that oblique and
disconnected logic ;) Seriously , hydrazine and azide are like flip sides of the same coin with regards to any labscale methods for azides . So the
two seemingly divergent topics will remain closely related and indeed interrelated , since the azides are daughter compounds of hydrazine .
Even the tetrazoles are family relations .
It always comes back to hydrazine as
the key precursor in convenient syntheses for these materials .

I think it was all the discussion earlier about the *preliminary* synthesis of hydrazine sulfate , which was " off topic " with regards to azides , yet several on topic posts related to azides from hydrazine were moved over to the hydrazine thread when those half dozen posts may still actually belong here .

Anyway , with regards to the freebasing of
hydrazine and then its subsequent basification further with added NaOH :
You need to limit the stoichiometric excess of NaOH used in the initial freebasing to a few percent , maybe 10%
at most NaOH in excess of theory , and after doing your multiple extractions with
fresh portions of alcohol , then add your
adjusted equivalent molar amount of NaOH to the combined extracts , so that your combined total of NaOH is only about 5% maximum in excess on a molar basis , above the theoretical requirement for the nitrosation reaction . The residual water
content in the NaOH will make the actual
excesses slightly lower , so these are good working proportions . When you use too great an excess of NaOH in the freebasing , then the excess NaOH is going to be hydrophilic and complicate the extraction . And if there is too much excess of NaOH in the extract during the nitrosation , then it will preferentially hydrolyse the organic nitrite to form the alkali nitrite which will precipitate along with the sodium azide formed later as
a contaminated and reduced yield second product .

For example , if you were freebasing a mole of HS , use a total of 88 grams NaOH for the freebasing . Then add 34 grams of NaOH to the combined extracts prior to the nitrosation . Do not dissolve your 34 grams of NaOH in a separate portion of alcohol , but simply add the solid NaOH in portions to the chilled extracts until all is in solution . On standing overnight in the cold , a small amount of undissolved precipitate , carbonate impurity from the NaOH and sodium sulfate carried over from the extractions will settle out and the clear solution may be decanted leaving most of the small precipitate adhering to the bottom
of the flask . From the basified hydrazine in alcohol the NaN3 should separate in very pure condition . The drier the extract , the less will be the tendency for the azide to precipitate as an adherent layer which sticks to the glass .

[Edited on 6-5-2005 by Rosco Bodine]
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