Organic 2 Review Problem 223

Organic 2 Review Problem 223 - P REPARATIONS 207...

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PREPARATIONS 207 Diazoaminobenzene. C 6 H 5 -N:N -NH -C 6 H 5 . Diazonium salts couple readily with aromatic primary amines, giving diazo- amino compounds. If for instance an aqueous solution of aniline sulphate is diazotised with a deficiency of nitrous acid, only part of it is converted into benzenediazonium sulphate and the latter then couples with the unchanged aniline to give diazoaminobenzene. The reaction is carried out at the opti- C 6 H 5 NH 2 ,H 2 S0 4 + HONO = C 6 H 6 N 2 HSO 4 + 2H 2 O C 6 H 5 N 2 4 -r HXHC 6 H 5 -> C 6 H 5 -NiN-NH-C 6 H 5 } H 2 SO 4 mum temperature of 30°, for at this temperature coupling takes place readily, and the diazonium sulphate is used up before it has time to decompose. Dissolve 2 ml. (3-7 g.) of concentrated sulphuric acid in 350 ml. of water contained in a 600 ml. beaker, and then add with stirring 12 ml. (12-3 g.) of aniline. Place the beaker in a water- bath and heat the latter gently until a thermometer in the solution records a temperature of 30°. Dissolve 4*5 g. of sodium nitrite in 15 ml. of water, and add about
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