Identity the compound 'D' in the following series of reactions.
$$CH_{3}-CH_{2}-Br \overset{alc. KOH}{\rightarrow}  'A' \overset{Cl_{2}/CCI_{4}}{\rightarrow}  'B' \overset{NaNH_{2}}{\rightarrow}  'C' \xrightarrow[1percentHgSO4]{40percentH2SO4}  'D'$$

Solution