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A hydrocarbon (X) discharges the colour ...

A hydrocarbon (X) discharges the colour of cold alkaline `KMnO_4` solution and reacts with warm dilute sulphuric acid containing `HgSO_4` to form another compound (Y). (Y) gives positive iodoform test but does not react with Tollens' reagent. (Y), when distilled with 80% `H_2SO_4`, gives sym-trimethylbenzene. Identify the compounds (X) and (Y) and write the reactions involved with proper reasons.

Text Solution

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The compound (X) discharges the colour of cold dilute alkaline `KMnO_(4)` solution. So it many be an unsaturated hydrocarbon. Since (X) reacts with dilute `H_(2)SO_(4)` to yield a carbonyl compound (Y) which gives positive iodoform test but does not react with Tollens' reagent, the carbonyl compound must be a ketone containing a `CH_(3)CO-` group and the unsaturated hydrocarbon (X) is a terminal alkyne `(R - C -= CH)` which , on hydration, produces a methyl ketone `(RCOCH_(3))`. Now, the alkyne, when distilled with 80% `H_(2)SO_(4)`, gives sym-trimethylbenzene. Hence, the terminal alkyne (X) is propyne. Naturally, the ketone (Y) is acetone, `CH_(3)COCH_(3)`.
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