Sciencemadness Discussion Board

Please confirm

swl - 9-10-2003 at 05:50

Can I prepare semicarbazide from the reaction between urea ,NaOCl , NaOH?

Please confirm me more than 5 persons.:)

First confirmation

Mephisto - 10-10-2003 at 07:34

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]

Marvin - 14-10-2003 at 05:03

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.

Rosco Bodine - 21-3-2013 at 09:15

Quote: Originally posted by Marvin  
I cant help but think asking for 5 replies is a tad cheeky.


Cheeky is okay :D
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 :P Just be patient ...
....processing ....processing..... :D

elementcollector1 - 21-3-2013 at 18:25

What was the point of bringing this thread back all the way from Tartarus?

Rosco Bodine - 21-3-2013 at 19:17

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 :D

Been picking away at it bit by bit for ten years so humor me.

AndersHoveland - 21-3-2013 at 22:44

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.

madscientist - 26-3-2013 at 17:56

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.

Rosco Bodine - 28-3-2013 at 01:25

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 :D ....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]