Semicarbazide acetate

Dissolve 7 g. of pure oleic acid in 30 ml. of dry ethyl chloride (chloroform may be used but is less satisfactory), and ozonise at about —30°. Remove the solvent under reduced pressure, dissolve the residue in 50 ml. of dry methyl alcohol and hydrogenate as for adipic dialdehyde in the presence of 0 5 g. of palladium - calcium carbonate. Warm the resulting solution for 30 minutes with a slight excess of semicarbazide acetate and pour into water. Collect the precipitated semicarbazones and dry the... 

A-Homo-5a-cholestan-4-one (3b). A solution of sodium nitrite (2 g) in water (100 ml) is added over 1 hr to a stirred solution of 3-(5 -spiro-2, 2 -dimethyloxazolidinyl)-5a-cholestane (7 4.58 g) in aqueous 10% acetic acid (800 ml), maintained at 0-5° for 3 hr and the mixture is then allowed to stand overnight. The reaction mixture is neutralized with 10% sodium hydroxide solution and the resulting white suspension is extracted with ether. The ether extracts are washed with water, dried and concentrated to give a semisolid residue which is converted to the semicarbazone by warming in methanol solution (ca. 65 ml/g) with an excess of methanolic semicarbazide-acetate solution. The precipitate of semicarbazone is recrystallized from ethanol to give a white powder mp 239-241°. A solution of hydrochloric acid (50 ml) in ethanol (450 ml) is added to the semicarbazone and the mixture is heated at reflux for 1 hr. The clear solution is diluted with water (250 ml) and the... 

Cyclic diacetylenes. A useful route to cyclic diacetylenes involves reaction of a cyclic diketone such as 1 with semicarbazide acetate in ethanol to afford 2. Reaction of 2 with Se02 forms selenadiazoles (3 and 4), which on thermolysis affords cyclic diacetylenes 5 and 6. 

Aldehydes and ketones may frequently be identified by their semicarbazones, obtained by direct condensation with semicarbazide (or amino-urea), NH,NHCONH a compound which is a monacidic base and usually available as its monohydrochloride, NHjCONHNH, HCl. Semicarbazones are particularly useful for identification of con jounds (such as acetophenone) of which the oxime is too soluble to be readily isolated and the phenylhydrazone is unstable moreover, the high nitrogen content of semicarbazones enables very small quantities to be accurately analysed and so identified. The general conditions for the formation of semicarbazones are very similar to those for oximes and phenylhydrazones (pp. 93, 229) the free base must of course be liberated from its salts by the addition of sodium acetate. 

Required Semicarbazide hydrochloride, i g. anhydrous sodium acetate, 0-9 g. acetophenone, i ml. 

Add first I g. of powdered semicarbazide hydrochloride and then 0 9 g. of anhydrous sodium acetate (or 1-25 g. of the crystalline acetate) to 5 ml. of water, and warm gently until a clear solution is obtained. Then add a solution of i ml. (i g.) of acetophenone in 5 ml. of rectified spirit, and warm the mixed solutions gently on a water-bath for... 

A) Semicarbazones. Prepared according to the directions given for acetophenone semicarbazone (p. 258), but use twice the amount of semicarbazide hydrochloride and sodium acetate. (M.ps., p. 549.)... 

Semicarbazones. Dissolve 1 g. of semicarbazide hydrochloride and 1 5g. of crystallised sodium acetate in 8-10 ml. of water add 0 - 5-1 g. of the aldehyde or ketone and shake. If the mixture is turbid, add alcohol (acetone-free) or water until a clear solution is obtained shake the mixture for a few minutes and allow to stand. Usually the semicarbazone crystallises from the cold solution on standing, the time varying from a few minutes to several hours. The reaction may be accelerated,... 

Prepare a solution of 1-0 g. of semicarbazide hydrochloride (NHjCONHNHj.HCl) and 1 - 5 g. of crystallised sodium acetate in 10 ml. of water in a test-tube. Add 1 ml. of acetone, close the tube with a cork and shake vigorously. Allow the mixtm e to stand, with occasional vigorous shaking, for 10 minutes it is advantageous to cool in ice. Filter the crystals, wash with a little cold water, and recrystallise from water or dilute alcohol. The m.p. of acetone semicarbazone is 187°. 

In order to obtain the free semicarbazide, 5-5 g. of the hydrochloride are ground in a small mortar with 4-5 g. of anhydrous sodium acetate (see p. 127). The paste produced by the formation of free acetic acid is transferred with a spatula to a 100 c.c. conical flask the last portions are washed in with absolute alcohol and the contents of the flask are then boiled on the water bath with (altogether) 50 c.c. of absolute alcohol. During the boiling the flask is frequently... 

The glycine, p)Tidine, acetic anhydride, and semicarbazide hydrochloride employed were of reagent grade and were used directly as supplied. 

CH3CH(N3)C(CH8) NNHCONH3 mw 170.17, N49.38% plates(benz or pet eth), mp 94° si sol in w, sol in usual organics. Prepd from a-azidoethyl methyl ketone and semicarbazide hydrochloride in the presence of sodium acetate and w... 

Trace polonium is extracted from aqueous acetate solution by 8-hy-droxyquinoline in chloroform, probably forming a 1 1 compound this sublimes at 140°C (81). The thionalide complex appears to have 2 molecules of ligand to each polonium atom volatile complexes with thiourea, thio-semicarbazide, diphenylcarbazide, and analogous reagents have also been reported (81). 

Semicarbazones are prepared by dissolving semicarbazide hydrochloride (ca Ig) and sodium acetate (ca 1.5g) in water (8-lOml) and adding the aldehyde or ketone (0.5-lg) and stirring. The semicarbazone crystallises out and is recrystallised from ethanol or aqueous ethanol. These are hydrolysed by steam distillation in the presence of oxalic acid or better by exchange with pyruvic acid (Hershberg dOC 13 542 1948). 

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