Organic 2 Review Problem 209

Organic 2 Review Problem 209 - PREPARATIONS I 9 3 with 70%...

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Unformatted text preview: PREPARATIONS I 9 3 with 70% sulphuric acid (preparation, p. 109), but the benzoic acid volatilises in the steam and crystallises again in the reflux condenser, which may become choked with a hard deposit of the acid: moreover some aromatic nitriles are liable to undergo sulphonation as well as hydrolysis when boiled with such concentrated sulphuric acid. These disadvantages do not apply to hydrolysis by sodium hydroxide, as the benzoic acid remains in solution as sodium benzo ate: furthermore, the completion of the hydrolysis is readily detected by the complete disappearance of oily drops of the insoluble nitrile. Boil 5 ml. (5-1 g.) of benzonitrile and 75 ml. of 10% aqueous sodium hydroxide in a 200 ml. flask under a reflux water-condenser until no more oily drops of unchanged nitrile run down from the condenser (usually about 40 minutes). Then detach the condenser and boil the solution in the open flask for a few minutes to remove free ammonia, Cool the liquid, and add concentrated hydrochloric acid...
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