STUDIES RELATED TO THE SYNTHESIS OF CHLORAMPHENICOL.Ⅶ STUDIES ON THE SYNTHESIS OF METHYL DICHLORACETATE

Cyanide catalysed dehydrohalogenation of chloral (probably chloral methanolate) by a suspension of anhydrous sodium carbonate in methanol was exploited as the simplest way for a one step synthesis of methyl dichloracetate. Chloral (1 mol.) was dropped as rapidly as possible into a suspension of anhydrous sodium carbonate (0.52 mol.) in methanol (110 ml.) containing 4 per cent its weight of potassium cyanide (5.9 g) when an energetic reaction set in almost instantly. The temperature of the reaction was kept at 60-64°. By finishing the reaction off in within about half an hour's time then cooled rapidly down to 20°, the oily ester layer was separated, washed with water, dried and fractionated. A yield of over 70% theory was obtained. However, hydrolytic fission of chloral into chloroform was shown to be competitive, when the concentration of cyanide ion present was reduced. Since equally good results could be obtained by first forming chloral methanolate, and then adding it to anhydrous sodium carbonate in methanol containing potassium cyanide;and since the reaction was rapid,and decomposition of chloral methanolate into chloral and methanol seemed improbable under the experimental conditions used, a new explanation of the mechanism of reaction was suggested as following: