chloric1
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Semicarbazide and Nitrites
I realize that Alkyl azides result from Hydrazine hydrate on Alkyl nitrites. What I wondering is if anyone knows what would happen between
semicarbazide and inorganic or alkyl nitrite? IT is tempting to get excited at what looks like a hydrazine molecule attached to a urea molecule.  I was
reading about hydrazine generation by semicarbazide and liquid ammonia and dilute acids under pressure. Why not semicarbazide and sodium nitrite
with an acid? ANyone have thoughts on this?
Fellow molecular manipulator
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BromicAcid
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Semicarbazide can be converted by hydrazine by a gross excess of ammonia, 74 molecules of ammonia to every one of semicarbazide. Acid hydrolysis is
much easier: | Quote: | | Hydrolysis of semicarbazide could be achieved in 6 M sulfuric acid, resulting in the sparsely soluble hydrazinium(2+)sulfate. This reaction is almost
quantitative, whereas the ammonolysis resulted in an equilibrium mixture from which pure hydrazine could not be obtained. |
From “Hydrazine and its Derivatives : Preparation, Properties, Applications” by Eckart Walter Schmidt the entry goes on to
state that although the conversion is easy, semicarbazide is made by the same processes as hydrazine and it is easier to just make the hydrazine in
that process then to isolate semicarbazide as an in-between step.
So, it at least sounds feasible, do you have some incredible source of semicarbazide?
[Edited on 1/18/2005 by BromicAcid]
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chloric1
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It is a 3 step process
Well, I do not have semicarbazide but I do have urea and converting it to nitrourea and reducing seems simple enough. But I may have more use for
Aminoguanidine anyways. I have access to "Chemical Reviews" at work and I downloaded a 59 page article called appropiately "The
Chemistry of Aminoguanidine" . It can be diazinated to guanyl azide and refluxed with alkali to produce the alkali azide!
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LUEshi is my god
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I've seen people refer to (Though never actually a complete synthesis, so i dunno if it's really been done or if it's just theoretical)
semicarbazide + XNO2 producing azides, according to NaNO2 + H2NCONHNH2 --> NaN3 + CO2 + NH3 + H2O. I wouldn't add an acid to semicarbazide +
NaNO2 unless you're sure no NaN3 is being produced, due to the unfriendliness of HN3.
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Theoretic
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A good way of producing semicarbazide(apart from reduction of nitrourea) could be reacting urea with chloramine, like with ammonia to form hydrazine.
Guanidine could probably be reacted with chloramine to give aminoguanidinium chloride, this you could react with NaNO2 (is that what diazination is?)
to give guanyl azide, this could be alkalysed to gie NaN3, then the resulting urea could be again reacted with NaNO2 to give more NaN3, one reaction
using the leftovers of the other.
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agent_entropy
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Can anyone direct me to an actual procedure for synthesizing semicarbazide (preferably the hydrochloride), I've looked and searched but I can't find a
complete procedure anywhere. I was looking for the Zn/HCl reduction of nitrourea method.
Does anyone know for sure if the urea/chloramine method that Theoretic mentioned actually works? And if so where could one find that procedure? I'm
wondering because the Kirk Othmer Encyclopedia of Chemical Technology says that in a modified form of the Raschig process for hydrazine, urea can be
used as the source of nitrogen instead of ammonia. So with that technique one might end up with hydrazine and something else instead of
semicarbazide.
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Axt
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Reduction of nitrourea with Zn/HCl and extraction as acetone semicarbazone is attached. React the semicarbazone with HCl to give semicarbazide
hydrochloride. Its an old german paper, but I had chemoleo translate the prep details which I added to the end of the pdf.
It works, though boiling hydrazine with urea, boiling to viscous liquid, pouring into methanol and precipitating with HCl is much easier.
[Edited on 27-7-2007 by Axt]
Attachment: reduction of nitrourea to semicarbazide.pdf (298kB)
This file has been downloaded 962 times
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agent_entropy
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Thanks, Axt. Actually that does sound much easier; I suppose the procedure for that method is just as simple as you put it? Does there have to be an
excess of anything for that to work, or just use stoichiometric quantities?
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Axt
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I used 130% excess of 51% hydrazine and "refluxed" for 3 hours. By "refluxed" i mean covering the beaker in cling wrap with a pin hole to allow NH3 to
escape for those 3 hours then removing and allowing to boil off. This seemed to give relatively pure semicarbazide with no noticable
hydrazodicarbonamide which is insoluble in methanol.
[Edited on 27-7-2007 by Axt]
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Rosco Bodine
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Here's more .....
Never tried it but hydrazine sulfate plus a cyanate gives semicarbazide .
http://www.sciencemadness.org/talk/viewthread.php?action=att...
The cyanate can be made from urea and a carbonate IIRC . I'll try to dig up that reference ...seems like there were a couple of ways of doing it
....one by simple melting
together .....and another reaction run in solution in DMSO .
[Edited on 26-7-2007 by Rosco Bodine]
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agent_entropy
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Axt:
When you say "130% excess" do you mean 1.3 or 2.3 molar equivalents? (urea being 1 of course)
Did you use hyrazine as the free base, hydrate, or an acid salt/complex?
Also, does "51% hydrazine" mean that you dissolved the urea in a 51% aqueous hydrazine solution?
BTW: I like that "reflux" apparatus. 
Rosco Bodine:
Cyanate by simply melting urea with a carbonate? Cool.
I get a blank screen when I click on the link you've posted...
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Axt
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Yep sorry, 1:1.3 mole ratio. A bit excess to avoid hydrazodicarbonamide and the assumption some will be lost during such crappy reflux. Yep, I meant
urea was dissolved into the 51% aqueous hydrazine (~80% hydrazinium hydroxide).
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agent_entropy
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Would it still work with a hydrazinium sulfate solution? Or would that produce semicarbazide sulfate? (Is there such a thing?... never heard of it...)
(I guess now I have to decide on a method of producing hydrazine...)
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Rosco Bodine
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Hydrazine Sulfate reduction of Nitrourea to Semicarbazide
This would probably be of interest also
http://www.sciencemadness.org/talk/viewthread.php?tid=3576&a...
The patent GB790066 describes a very interesting method of producing what is probably semicarbazide sulfate from a reaction of equimolar amounts of
hydrazine sulfate and nitrourea in an aqueous system with nitrous oxide being evolved as a byproduct. The patent description is not very
comprehensive so here I am doing some "reading between the lines" hopefully with understanding that is correct.
Semicarbazide sulfate would seem to be desirable as a prescursor for carbamoyl azide via nitrosation with sodium nitrite. The sulfate could be
removed from the reaction mixture by use of hydrated lime or perhaps calcium nitrate.
The glauberite precipitation scheme for sulfate removal may be useful here, but I have not checked this to be sure.
http://www.sciencemadness.org/talk/viewthread.php?tid=1987&a...
The filtered carbamoyl azide solution should upon heating decompose to a solution of ammonium azide, which may be obtained upon evaporation as a
stable non hygroscopic crystalline solid. Or the ammonium azide may be converted to sodium azide by addition of NaOH or perhaps in the alternative
sodium carbonate or bicarbonate, and boiling to expel byproduct ammonia, eavaporating to dryness to obtain the sodium azide.
Attachment: GB790066 Semicarbazide from Nitrourea and Hydrazine Sulfate.pdf (361kB)
This file has been downloaded 474 times
Attachment: US1343443 Glauberite_CaSO4 - Na2SO4 double salt.pdf (103kB)
This file has been downloaded 486 times
[Edited on 29-3-2013 by Rosco Bodine]
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AndersHoveland
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possible (untested) route for preparing azide via urea
| Quote: | 9 grams of urea nitrate, was added in small portions to 32 mLof ice cold (-3 C) concentrated sulfuric acid at such a rate that the temperature did not
exceed 5 C. Total time for addition was approximately one-half hour, after which the mixture was poured on 75 grams of ice. The white precipitate was
filtered, washed with ice cold water, just sufficient to cover it, and air dried. Material obtained weighed 5.3 grams and melted with decomposition at
157-158 C.
20g of nitrourea, 65g of zinc dust and 10 mL pure methanol (without water) are mixed in mortar and ground into a thick paste. A glass beaker is filled
with 12 ml of glacial acetic acid and 15 mL pure methanol, then placed into an ice water bath. The cold nitrourea and zinc paste is added in small
portions with gentle stirring. The reaction will give off much heat, so the initial portions should be smaller, and added over longer intervals of
time, so the mixture does not overheat. The rate of addition should be adjusted to keep the temperature from rising too much, ideally around 10 degC.
Do not allow the temperature at any time to rise to 35C. If the mixture becomes too thick or the temperature rises too rapidly, cold methanol should
be added (no more than 50g). The additions to the paste should be done over a time of around 3 hours.
After completion, the beaker containing the reaction mixture should be allowed to stand in ice water bath for another hour. The beaker is then removed
from bath and allowed to warm slowly to normal temperature. The final volume of the mixture should be around 130 mL. After one hour at room
temperature, the mixture is placed on water bath, heated to 25 degC, and stirred for 30 minutes, then heated to 32-35C, and stirred for 30 more
minutes, finally being heated to 40 degC and stirred at this temperature for another 15 minutes.
When the reduction reaction is complete, the solution is immediately filtered using a vacuum funnel, and filtering the solid product dry. The solid is
washed with 90 mL of water, then filtered. The solids left over are discarded. The filtrates (solution that dissolved out the semicarbazide and passed
through the filter paper) are combined. The solution will contain around 10g of dissolved semicarbazide. The yield for the reaction of nitrourea to
semicarbazide at this point is 60%)
Dilute sulfuric acid (5% solution) is added to the solution until the pH just reaches 6.5. It is important that the resulting solution not be too
acidic or contain excess acid. It may be helpful to pre-cool the acid solution.
9.2g of Sodium Nitrite is separately dissolved in 125 mL water, and this solution is reacted with the semicarbazide sulfate solution (which contains
the equivalent of 10g semicarbazide). The addition should be slowly done, over the period of roughly ten minutes, the temperature should be kept below
20 degC, but ideally 10 degC is good. The reaction may give off some poisonous vapors so do it outside or in a fumehood. After this reaction,
immediately proceed to the final step, which is to gradually add a pre-chilled concentrated solution of sodium hydroxide.
The resulting solution contains dissolved sodium azide, along with byproducts of sodium carbamate, and sodium sulfate (much of it will precipitate out
as solid crystals on the bottom below 15 degC).
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