Organic 2 Review Problem 320

Organic 2 Review Problem 320 - dull yellow colour....

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3°4 PRACTICAL ORGANIC CHEMISTRY Required: N-Phenylanthranilic acid, 4 g.; sulphuric acid, ioml. Prepare a mixture of 4 g. of N-phenylanthranilic acid and io ml. of concentrated sulphuric acid in a conical flask, and heat it for i£ hours on a steam-bath. Then pour the hot dark green solution slowly and cautiously into 200 ml. of boiling water in a 500 ml. beaker, allowing the acid to run down the side of the beaker to prevent "spattering". Then boil the mixture for 5 minutes, and filter it whilst hot through a Buchner funnel, and wash the acridone on the filter with hot water. For puri- fication, transfer the acridone to a solution of 4 g. of hydrated sodium carbonate in 50 ml. of water, boil the mixture for 5 minutes, and then filter it whilst hot: wash the acridone with boiling water and dry thoroughly. Yield, almost theoretical (3 -7 g.). The acridone, m.p. 345-346°, thus prepared has usually a rather
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Unformatted text preview: dull yellow colour. Recrystallisation from acetic acid using char-coal, or (better) sublimation as described on p. 23, gives the bright yellow product: the sublimed material has m.p. 351 -352. Quinoxalines. (Semi-micro Scale.) o-Phenylenediamine condenses readily with i,2-diketones to give the corres-ponding 2,3-disubstituted quinoxalines. Thus benzil (preparation, p. 234) gives 2,3-diphenylquinoxaline: phenanthraquinone (II) (see p. 370) gives the corresponding derivative (III). (II) (HI) This rapid formation of the crystalline quinoxaline derivative can therefore be used to identify i,2-diketones: conversely, a nuclear-substituted o-phenyl-enediamine can be identified by the quinoxaline derivative which it forms with a known i,2-diketone such as benzil....
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