Benzene from phenylhydrazine

Experiment. Benzene from Phenylhydrazine.—Allow 5 g. of phenylhydrazine, dissolved in a mixture of 5 c.c. of glacial acetic acid and 10 c.c. of water, to run slowly into an ordinary distilling flask in which a solution of 25 g. of copper sulphate in 75 c.c. of water is heated to the boiling point. A downward condenser is attached to the flask. A vigorous evolution of nitrogen takes place and the benzene at once begins to distil with the steam. Collect and purify (as described on p. 286). Yield 2-3 g. 

Benzene from phenylhydrazine, 223. Benzcnesulphinic acid, 258. Benzenesulphon amide, 253. 

Dissolve 0-2 g. of fructose in 10 ml. of water, add 0-6 g. of cw-methyl-phenylhydrazine and sufficient rectified spirit to give a clear solution. Since the fructose may not be quite pure, warm the mixture slightly, allow to stand, preferably overnight, so that any insoluble hydrazones may separate if present, remove them by filtration. Add 4 ml. of 50 per cent, acetic acid to the filtrate it will become yellow in colour. Heat the solution on a water bath for 5-10 minutes, and allow to stand in the dark until crystalUsation is complete it may be necessary to scratch the walls of the vessel to induce crystalUsation. Filter the crystals and wash with water, followed by a little ether. RecrystaUise the orange-coloured methylphenylosazone from benzene m.p. 152°. 

Phenylhydrazones (compare Section III,74,C). Dissolve 0-5 g, of colourless phenylhydrazine hydrochloride and 0 8 g. of sodium acetate in 5 ml. of water, and add a solution of 0-2-0-4 g. of the aldehyde (or ketone) in a little alcohol (free from aldehydes and ketones). Shake the mixture until a clear solution is obtained and add a little more alcohol, if necessary. Warm on a water bath for 10-15 minutes and cool. Filter ofiF the crystalline derivative, and recrystalhse it from dilute alcohol or water sometimes benzene or light petroleum (b.p. 60-80°) may be used. 

The free base is liberated by adding to the phenylhydrazine hydrochloride 1 1. of a 25 per cent solution of sodium hydroxide. The phenylhydrazine separates and is taken up with benzene (two 300-cc. portions). The combined extractions are well dried with 200 g. of solid sodium hydroxide, poured off, and distilled. Most of the benzene may be distilled under ordinary pressure, and the remainder, and any low-boiling impurities, under diminished pressure. The pure phenylhydrazine boils at 137-138°/18 mm., and is obtained as a pale-yellow liquid. It can be crystallized on cooling in an ice bath the crystals melt at 23°. The crude phenylhydrazine from two lots of aniline... 

To a suspension of 1.7 g (6.2 mmol) 2,6-dibenzylidenecyclohexanone 1 in 70 ml of ethanol 0.7 ml (6.2 mol) of phenylhydrazine was added and the mixture was refluxed for 2-3 h until the initial ketone had completely disappeared, then the solvent was evaporated and the residue was diluted with benzene and chromatographed on an A1203 column with benzene (Scheme A. 14). The first fraction eluted exhibited luminescence and contained 2,3-diphenyl-7-benzylidene-3,3a,4,5,6,7-hexahydro-2//-indazole 2. After evaporation of the solvent and crystallization from a mixture of ethanol and benzene, 1.35 g (60%) of 2 with a melting point of 157-159°C was obtained. The next fraction was evaporated and 0.56 g (25%) of l,3-diphenyl-7-benzylidene-3,3a,4,5,6,7-tetrahydroindazole 3 with a melting point of 175-177°C was obtained. 

A number of by-products may be isolated from sodium stannite reductions. In addition to benzene, aniline gives phenol, azobenzene, phenyl azide, and phenylhydrazine.107 10 108 109 The danger of hydrolytic cleavage in alkaline media, previously discussed in connection with the... 

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