Problem 2

An oily liquid A is insoluble in water, but on heating with aqueous sodium hydroxide solution for half an hour it dissolves. From the reaction mixture a liquid B can be distilled, which gives a yellow precipitate with iodine and sodium hydroxide solution. On careful oxidation B gives an aldehyde, C, which also gives a yellow precipitate with iodine and sodium hydroxide solution. If sulphuric acid is added to the solution obtained from heating A with sodium hydroxide solution, a white precipitate D is obtained. D liberates carbon dioxide from sodium hydrogen carbonate solution, one mole of D reacting with sodium hydrogen carbonate to give one mole of carbon dioxide. Heating D with soda-lime* converts it to benzene.

Find the structures of A, B, C and D, giving your reasoning.

* Soda-lime is calcium oxide that has been slaked with sodium hydroxide solution. Carboxylic acids, on heating with soda-lime, are decarboxylated, that is the -COOH group is replaced by -H.

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