Organic 2 Review Problem 225

Organic 2 Review Problem 225 - P REPARATIONS 209 pump a nd...

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PREPARATIONS 209 pump and wash well with water. Aminoazobenzene is freely soluble in methylated spirit, although insoluble in water. For recrystallisation, therefore, dissolve the crude substance in boiling methylated spirit, remove from the water-bath, and then add water drop by drop until the solution becomes just cloudy owing to the separation of the solute: replace the solution momentarily on the water-bath until the cloudiness disappears, and then at once remove the solution, and allow it to cool slowly. (Alternatively, the crude dry material can be recrystallised from carbon tetrachloride in the usual way.) Aminoazobenzene is thus obtained as yellowish-brown crystals, m.p. 126°: yield, 5 g. To prepare the hydrochloride, add about i g. of amino- azobenzene to 200 ml. of dilute hydrochloric acid and boil until nearly all the solid material has dissolved. Filter hot and allow to cool slowly. Aminoazobenzene hydrochloride separates as beautiful steel-blue crystals: filter and dry. If a small quantity
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