Carbazide

B) Semicarbazones. These often form readily in the cold (see above) if not, employ a reasonably short period of heating, othervvise carbazide, ( NH CO-NH2)2, m.p. 244°, may beformed and may separate. 

If in the Hantzsch s synthesis, selenoamide is replaced by a selenosemi-carbazide (HjJN -NH-CSe-l ). condensation can take place upon... 

A third approach to 3-amino-/3-lactams is by Curtius rearrangement of the corresponding acyl azides. These are readily prepared from r-butyl carbazides, available via photochemical ring contraction of 3-diazopyrrolidine-2,4-diones in the presence of f-butyl carbazate (c/. Section 5.09.3.3.2). Thus treatment of (201) with trifluoroacetic acid followed by diazotiz-ation gives the acyl azide (202) which, in thermolysis in benzene and subsequent interception of the resulting isocyanate with r-butanol, yields the protected 3-amino-/3-lactam (203) (73JCS(P1)2907). 

Triazole-3(5)-thiol has been prepared by heating thio-semicarbazide and formic acid, by heating l-formyl-3-thiosemi-carbazide, and by heating 1,3,5-triazine and thiosemicarbazide. The ring closure of l-formyl-3-thiosemicarbazide using aqueous base was suggested by L. F. Audrieth and F. Hersman. 

Chromium (total and speciated chromium) in chromium plated mists Colorimetric field method using 1,5-diphenyl carbazide after oxidation with silver (1 (-catalysed peroxydisulphate 67... 

Diketones with Diamines—qiiinazolines 11. Diketones with NH OH—isoxazolines 12. Diketones with NH NH,—pyrazoles 13. Diketones with semi-carbazide—pyrazoles 14. Diketones with ammonia—pyrazoles 15. Carbon disulfide with ammoacetamide—thiazolone 16. Nitriles and ethylene diamines—imidazolines D D D D D A D ... 

An acetoxy group at C-21 inhibits reaction of the 20-ketone with semi-carbazide hydrochloride,but in buffered medium 20-semicarbazones can be prepared in high yield even from 17-hydroxy-21-acetoxy compounds. ... 

Neuberg and Tiemann propose the following method, depending on the fact that most aldehydes form a compound with thiosemi-car-bazide. The oil containing aldehyde is heated in alcoholic solution on a water-bath, with thiosemi-carbazide. Various salts of the heavy metals will form insoluble precipitates with the thiosemi-carbazone formed, and such precipitate is dissolved in alcohol, and a current of hydrogen sulphide passed through until the metal is precipitated, leaving the thiosemi-carbazone dissolved in the alcohol. 

Semi-carbazones.—Most aldehydes react with semi-carbazide, forming... 

They are usually best obtained by dissolving the aldehyde in alcohol, and adding excess of an equimolecular mixture of semi-carbazide hydrochloride, and acetate of sodium. The mixture is allowed to stand for some time and the ssmi-carbazone then precipitated by the addition of water. Some semi-carbazones are more easily prepared by substituting free acetic acid (glacial) for the acetate of sodium. Semi-carbazones are beat recrystallis from hot methyl alcohol. 

For the identification of citronellal, the semi-carbazone is the easiest cry stalline compound to prepare. It results if an alcoholic solution of citronellal be well-shaken with a solution of semi-carbazide hydrochloride and acetate of sodium. It is purified by recrystallisation from a mixture of chloroform and petroleum ether, and then melts at 84°. It also forms a well-defined naphthocinchoninic acid, which is prepared in the same manner as the corresponding citral compound. It melts at 225°. 

It forms a semi-carbazone melting at 136° to 138°, which can be obtained as follows Ten c.c. of methyl-heptenone are dissolved in 20 c.c. of facial acetic acid, and a mixture of 10 grams of semi-carbazide hydrochloride and 15 grams of sodium acetate dissolved in 20 c.c. of water is added. After half an hour the semi-carbazone is precipitated by the addition of water, and recrystalUsed from dilute alcohol. 

N sodium hydroxide solution (5 ml) is added to a stirred suspension of S-methyllsothiosemi-carbazide hydroiodide (2.33 g) and hydroxylamine hydrochloride (0.70 g) In water (6 ml) and stirred for 48 hours. The solution is evaporated In vacuo to provide 1 -amino-3-hydroxy-guanidine. One-third of the residue is dissolved in 16 ml of ethanol and 2,6-dichlorobenzalde-hyde (0.6 g) Is added to this solution. The reaction mixture is then stirred for 48 hours. The solution is then evaporated in vacuo and the residue dissolved in ether (30 ml) and in hydrochloric acid (30 ml). The aqueous phase is rendered alkaline with 2 N sodium carbonate solution and extracted with ether. The ether layer is dried with sodium sulfate and evaporated. 

Analogous 1 H-, 3,4-benzotriazepine-2(3/7)-thiones are formed by the cyclization of thiosemi-carbazides derived from 2-aminoaryl ketones, e.g. formation of 11.355... 

The same reaction occurs on base treatment with aqueous potassium hydroxide. A simple carbazide can also be used, albeit resulting in lower yields.6... 

In the formation of tert-butyl azidoformate by the addition of phosgene to alcohols followed by the addition of Na nitride or hydrazoic acid in the presence of pyridine, reaction of phosgene with the azide can cause the formation of expl carbazide (Ref 9)... 

Carbonic acid dihydrazide, carbazide, or N,N-diaminourea C 0(NHNH2)2] has a MW of 90.1. It is available as a 98+% liquid or in various diluted forms, typically a 6.5% formulated product. 

Reducing the availability of GABA by blocking the synthesising enzyme GAD also promotes convulsions. This may be achieved by substrate competition (e.g. 3-mercapto propionic acid), irreversible inhibition (e.g. allylglycine) or reducing the action or availability of its co-factor pyridoxal phosphate (e.g. various hydrazides such as semi-carbazide). In fact pyridoxal phosphate deficiency has been shown to be the cause of convulsions in children. 

Next, the hydrazides 41a-e were used in synthesis of different 1,2,3-triazole-3-thiones and l,3,4-oxadiazole-2-thiones. Thus, treatment of 41 e with phenyl isothiocyanate in boiling temperature for 4 h gave the thiosemi-carbazide solid, which separated and boiled directly with 5% NaOH for 3 h to provide, after neutralization with dilute HCl, 55 (67%). Similarly, treatment of 41d with 4-methoxyphenylisocyanate afforded 51 (62%). 

Diaryl carbazides and thiocarbazides, e.g., 43, can be oxidized at alkaline pH to yield C-hydroxy or C-mercapto formazans (44) (Eq. 8).68,129 The replacement of C-halo formazans is considered to be a better method60 for the preparation of 44. A class of cyclic formazans (45) can be obtained by air oxidation of amidrazones (46) (Eq. 9) 9,73,101,102 jhough this is formally a formazan, there are no reports of its oxidation reactions. In a... 

Ferricyanide oxidation of 1,5-disubstituted thiocarbazones (116) give the mesoionic tetrazolium salts (117) under mild conditions (Eq. 21).190 This is in contrast to the strongly alkaline oxidation of carbazides leading to mercapto formazans as shown in Eq. 8 (Section 7.3.1.4). The heterocyclic triazine (118), obtained by the action of a diazonium salt on 2-... 

In a similar vein condensation with 2-ethylsemi-carbazide leads to the semicarbazone nitfursemi zone (26), an antiprotozoal agent for use in poultry. 

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