MeshPL
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Hydroxylamine synthesis + wargases mumbo jumbo
Asssume you want to make hydroxylamine. What you could try to do is (overall reaction, it actually proceeds in steps):
H2O + KNO2 + 2NaHSO3 --> NH2OH + KHSO4 + Na2SO4
By replacing salts with ammonium analogs and bubbling SO2 as bisulphate replacement, you may get hydroxylamine solution with relatively little
impurities. You may try to percipitate all sulphates with Ba(OH)2, drive away ammonia with more Ba(OH)2 as well and percipitate Ba with sulphuric
acid. You could try to obtain something relatively pure this way. Or settle down with impure solution with some salts along hydroxylamine. Commercial
hydroxylamine is sold as chloride so your will not be much worse.
But there may be an alternative process. Likely worse, but let's see it anyway.
1. Picric acid:
Everybody will agree that an amateur with relatively good chemical supply could make some. So I won't write much about it.
2. Chloropicrin
Picric acid, when chlorinated produces chloropicrin. (Trichloronitromethane) With sodium hypochlorite, the overall reaction is:
HOC6H2(NO2)3 + 11 NaOCl → 3 Cl3CNO2 + 3 Na2CO3 + 3 NaOH + 2 NaCl
Reference for synthesis with Ca(ClO)2: http://www.prepchem.com/synthesis-of-chloropicrin/
I wonder if TCCA could be used or if Cl2 could be simply bubbled through.
Apparently nitromethane can also be chlorinated allowing for more direct synthesis:
H3CNO2 + 3 NaOCl → Cl3CNO2 + 3 NaOH
Although picric acid may be easier to make. But definitely harder to buy, so one may opt for this route.
3. Phosgene oxime:
Chloropicrin can be reduced by tin and hydrochloric acid to make phosgene oxime. The overall reaction is:
Cl3CNO2 + 2 Sn + 5 HCl + H2O → Cl2C=N−OH + 2 H3O[SnCl3]
For this reaction I haven't found such a good reference. There is one for other reaction involving chlorinating mercury fulminate, but that sounds
like a recipe for a total disaster: http://www.prepchem.com/synthesis-of-phosgene-oxime/
4. Phosgene oxime can be hydrolysed. It's pretty straightforward:
Cl2CNOH + 2 NaOH → CO2 + NH2OH + 2 NaCl + H2O
I wonder, if it would also work:
Cl2CNOH + Ag2O → CO2 + NH2OH + 2 AgCl
EDIT no, it won't, hydroxylamine will reduce silver.
The advantages of this method of producing hydroxylamine would be somewhat vague:
-doesn't use nitrites (maybe in some country they are considered precursors [poppers!] and thus unavailable to general public)
-preparing pure NH2OH solution may be easier this way. There would be no need for percipitating salts with barium, although Ag2O is very expensive and
may actually not work. EDIT: Hydroxylamine will reduce silver. It wil not work.
The disadvantages are huge:
-much more labour consuming
-requires more reagents
-chloropicrin and phosgene oxime are dangerous as HELL. They were used as war gases. Picric acid as well as nitromethane and mercury fulminate for
other possible pathways are also no jokes.
So overall if that method even works (but in some way it likely does), it wouldn't be a safe, easy or cheapest route. Do you think that would at least
work?
[Edited on 1-11-2015 by MeshPL]
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UC235
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I have made hydroxylamine hydrochloride before. It makes gorgeous plates when recrystallized from water. Here is a relatively mediocre picture.
I used a combination of http://www.orgsyn.org/demo.aspx?prep=CV1P0318 and http://www.orgsyn.org/demo.aspx?prep=CV2P0204 for my prep along with a few personal tweaks.
I can't seem to find my notes on the prep, but I used the prep of the sodium hydroxylamine monosulfonate from the second orgsyn entry as it avoids
using SO2 gas. Instead of acetone, I used 2-butanone (MEK). MEK oxime is a liquid and has fairly low water solubility (also the aq phase is nearly
saturated with salt after the prep). The oxime is simply removed as the upper phase avoiding a long steam distillation at the cost of some yield (I
believe I had to neutralize excess acid before it would separate).
Optional vac fractionation of the oxime gives a pure product
The oxime is mixed with HCl and the MEK/water azeotrope is slowly removed through a fractionating column (hydrolysis is way slower than for azines
when making hydrazine), the solution is boiled down, and allowed to crystallize. I think I got about 55% from NaNO2. It is a lot of work, however.
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MeshPL
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Oh, I forgotten to mention oximes as a way of purification. Thanks! I guess with help of Ag2O, hydroxylamine hydrochloride can be turned into pure
solution if one needs it.
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unionised
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Quote: Originally posted by MeshPL  | | Oh, I forgotten to mention oximes as a way of purification. Thanks! I guess with help of Ag2O, hydroxylamine hydrochloride can be turned into pure
solution if one needs it. |
You might gues that.
I would guess that the silver oxide would be reduced to silver.
IIRC the "classic" way to get the free base is to dissolve the hydroxylammonium chloride in methanol and add a solution of KOH in methanol.
The KCl isn't soluble.. so you get left with an essentially pure solution of hydroxylamine in methanol.
It's not clear why you would normally bother to do this.
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MeshPL
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Oh, yes. Forgot that hydroxylamine is also a strong reducer. In fact, it is a very, very strong reducer.
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Boffis
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If you are trying to make hydroxylamine solution have you checked out Axt's paper in the prepublication section. He used the hydrolysis of
nitromethane with hydrochloric acid. This is the simplest route for amateurs though nitromethane is not so easy to get these days. If the final
product is free hydroxylamine solution then the sulphate is more useful and this is easily prepared by the bisulphite process and then free based with
barium hydroxide solution. You can also buy 50% hydroxylamine solution in the UK easily and fairly cheaply.
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shivam
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To reduce a bit of work, instead of using sodium bisulfite or bubbling SO2, I guess using sodium metabisulfite should also work
work fine.
More importantly, sodium metabisulfite is much more easily available for an amateur as a chemical for home-brewing.
As aqueous Na2S2O5 can be viewed essentially as a solution of sodium bisulfite for most reactions.
Na2S2O5 + H2O <==> 2 NaHSO3
[Edited on 3-11-2015 by shivam]
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Boffis
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Looking again at some of the IP's ideas. There is no need to isolate phosgene oxime to prepare hydroxylamine hydrochloride from mercury fulminate. The
latter is hydrolysis directly to hydoxylamine by hot dilute hydrochloric acid in a single step, the procedure was published more than 100 years ago.
The route through chloropicrin is hopelessly inefficient as many by products are also produced that reduce yield, I have some papers somewhere on the
reactions of chloro and bromopicrins.
Nop. For the amateur the best route is from sodium nitrite and sodium metabisulphite to hydroxylamine sulphate. There are several published procedure
but the one in Brauer (see Forum library) is as good as any.
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