Organic 2 Review Problem 321

Organic 2 Review Problem 321 - PREPARATIONS 305 (A) 2...

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PREPARATIONS 305 (A) 2,3-DIPHENYLQUINOXALINE Required: .V-Phenylanthranilic acid, 4 g.; sulphuric acid, 10 ml. Prepare a mixture of 4 g. of .Y-phenylanthranilic acid and 5 ml. of ethanol, and boil the solution under reflux for 20 minutes. Cool the mixture, when the 2,3-diphenylquinoxaline will rapidly crystallise. Filter off the quinoxaline at the pump, and recrystallise it from ethanol. It forms colourless crystals, m.p. 125°. Yield, i-o g. (B) THE QUINOXALINE (III) I ? e <7 u *' red :0-Phenylenediamine, 0*5 g.; phenanthraquinone, i g. Proceed as in (A), using 50 ml. of ethanol, with boiling for 20 minutes. The quinoxaline (III) crystallises readily during the boiling. Cool the mixture, filter off the quinoxaline, and wash it with ethanol. The dry product, of m.p. 220-225 °, weighs 1-3 g. Recrystallise the quinoxaline from chloroform or acetic acid; pale yellow crystals, m.p. 226°. Yield, 0-9-1-0 g. Both the above condensations can alternatively be carried out
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