Addition—Continual phthalide

Phthalide. In a 1 litre bolt-head flask stir 90 g. of a high quality zinc powder to a thick paste with a solution of 0 5 g. of crystallised copper sulphate in 20 ml. of water (this serves to activate the zinc), and then add 165 ml. of 20 per cent, sodium hydroxide solution. Cool the flask in an ice bath to 5°, stir the contents mechanically, and add 73-5 g. of phthalimide in small portions at such a rate that the temperature does not rise above 8° (about 30 minutes are required for the addition). Continue the stirring for half an hour, dilute with 200 ml. of water, warm on a water bath imtil the evolution of ammonia ceases (about 3 hours), and concentrate to a volume of about 200 ml. by distillation vmder reduced pressure (tig. 11,37, 1). Filter, and render the flltrate acid to Congo red paper with concentrated hydrochloric acid (about 75 ml. are required). Much of the phthalide separates as an oil, but, in order to complete the lactonisation of the hydroxymethylbenzoic acid, boil for an hour transfer while hot to a beaker. The oil solidifles on cooling to a hard red-brown cake. Leave overnight in an ice chest or refrigerator, and than filter at the pump. The crude phthalide contains much sodium chloride. RecrystaUise it in 10 g. portions from 750 ml. of water use the mother liquor from the first crop for the recrystaUisation of the subsequent portion. Filter each portion while hot, cool in ice below 5°, filter and wash with small quantities of ice-cold water. Dry in the air upon filter paper. The yield of phthalide (transparent plates), m.p. 72-73°, is 47 g. 

Cyanomethylbenzoic acid. This preparation must be conducted in an efficient fitme cupboard. Into a 1-litre three-necked flask, provided with a mechanical stirrer and a thermometer, place 40 g (0.33 mol) of phthalide and 40 g (0.615 mol) of powdered potassium cyanide (CAUTION). Heat the stirred mixture to 180-190 °C (internal temperature) in an oil bath for 4-5 hours. Allow to cool, add 400 ml of distilled water and stir the mixture until all the solids are dissolved (about 1 hour). Filter off any unreacted phthalide. Add dilute hydrochloric acid (1 1) to the dark aqueous solution (CAUTION hydrogen cyanide is evolved) until it becomes turbid (about 20 ml are required), and continue the addition until the solution is slightly acid filter off any dark impurities which may separate. Neutralise the solution carefully with sodium hydrogen carbonate, add a few grams of decolourising carbon, stir the mixture for several minutes and filter. Acidify the nearly colourless filtrate with about 20 ml of concentrated hydrochloric acid, cool in ice and filter at the pump. The resulting o-cyanomethylbenzoic acid (36 g) melts at... 

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