swl
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Please confirm
Can I prepare semicarbazide from the reaction between urea ,NaOCl , NaOH?
Please confirm me more than 5 persons.
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Mephisto
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First confirmation
Yes, thats possible. I suggest this way, but a shorter way could be possible.
1. Step: hydrazinium sulfate from NH3, NaOH, NaOCl and gelantine
2. Step: hydrazine hydrate form step 1 and KOH (or NaOH)
3. Step: semicarbazide from step 2 and urea [maybe useful: US patent 4,482,738]
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Marvin
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I cant help but think asking for 5 replies is a tad cheeky.
The only ways I know of making semicarbazide from hydrazine and urea I know need hydrazine hydrate, which is difficult enough to make in itself.
Though thats without looking at the suggested patent.
Using urea to make the hydraizine rather than ammonia would be a big improvement and I bilieve we owe Mr Anonymous for the currently accepted best
method.
A way that might work more directly, is that if you mix ammonia not in excess with hyperchlorite, you get chloramine in high yeild rapidly. If you
added this to a urea solution, you might get a good yeild of semicarbazide providing the urea was in large excess. Then your only hassle is to
seperate them.
If we restrict ourselves to the exact question though 'Can I prepare semicarbazide from the reaction between urea ,NaOCl , NaOH? ' *the*
reaction, ie a one step method, the answer is very probably, No.
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Rosco Bodine
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Cheeky is okay 
| Quote: |
The only ways I know of making semicarbazide from hydrazine and urea I know need hydrazine hydrate, which is difficult enough to make in itself.
Though thats without looking at the suggested patent.
Using urea to make the hydraizine rather than ammonia would be a big improvement and I bilieve we owe Mr Anonymous for the currently accepted best
method.
A way that might work more directly, is that if you mix ammonia not in excess with hyperchlorite, you get chloramine in high yeild rapidly. If you
added this to a urea solution, you might get a good yeild of semicarbazide providing the urea was in large excess. Then your only hassle is to
seperate them.
If we restrict ourselves to the exact question though 'Can I prepare semicarbazide from the reaction between urea ,NaOCl , NaOH? ' *the* reaction, ie
a one step method, the answer is very probably, No. |
No ? Hmmm I'm not so sure, but I'll look into it. This could take awhile, so let's hope the OP isn't in any hurry, nearly ten years and I'm the
third reply...Have no fear we shall get that answer for you straight away  Just
be patient ...
....processing ....processing.....
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elementcollector1
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What was the point of bringing this thread back all the way from Tartarus?
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Rosco Bodine
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It was to create suspense about new hydrazine related material just being investigated today ....and noticing it has been 10 years that yours truly
has been posting from time to time about what .....drum roll ....you guessed it
HYDRAZINE a very interesting material huh
Been picking away at it bit by bit for ten years so humor me.
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AndersHoveland
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I remember reading that the oxidation of urea by hypochlorite actually, surprisingly enough, forms just plain hydrazine. The reaction proceeds through
Hofmann rearrangement. I am not entirely sure if semicarbazide is also formed in this reaction, but I would think it would. If you want good yields of
semicarbazide, probably the best thing to do would be to bubble chloramine gas (made from bleach + NH4OH) into a solution of urea in methanol. The
absence of water will make the chloramine less likely to hydrolyze.
I would also think some diurea/azodicarbonamide would form from this procedure also.
I also think I remember reading that hydrazine hydrate can condense with urea to form semicarbazide, displacing an NH3, at ambient temperatures.
You might look in the sciencemadness library. There is a patent describing how semicarbazide can be made from urea. They say to first react the urea
with chlorine, and then add NaOH, and that this order of reaction steps is essential.
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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madscientist
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Got a reference for chloramine reacting with urea to give semicarbazide?
"I think I remember reading somewhere."
A flood of unverifiable information is less than nothing.
I weep at the sight of flaming acetic anhydride.
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Rosco Bodine
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Quote: Originally posted by swl  | Can I prepare semicarbazide from the reaction between urea ,NaOCl , NaOH?
Please confirm me more than 5 persons. |
And the answer is ......YES ....well sort of, you will need some ammonium
hydroxide, also some zinc chloride
http://www.sciencemadness.org/talk/viewthread.php?tid=1128&a...
See US5241117 Example 21 yield of semicarbazide 70%
[Edited on 28-3-2013 by Rosco Bodine]
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