A ketone A, which undergoes halform reaction, gives compound B on reduction B on heating with sulphuric acid gives compounds C, which forms mono-ozonide D.D on hydrolysis in the presence of zinc dust gives only acetaldehyde. Identify A, B and C. Write down the reaction involved.

Explanation

As the compound [A] gives haloform reactions, it contains `CH_(3)CO` group. Since the compound [C} forms a monozonide [D]. It must contain a double bond. As the monozonide [D} when hydrolysed in the presence of zinc dust gives only acetaldehyde `(CH_(3)-CH = O)`, this shows that the compound [C] is `CH_(3)-CH=CH-CH_(3)` i.e., but-2-ene. Since the compound [C] is obtained by the dehydration of [B], the compound [B] must be a secondary alchohol i.e., `CH_(3)CH(OH)CH_(2)CH_(3)`. As the compound [B] is obtained by the reduction of [A] which also contains `CH_(3)CO`-group, the compound [A] is `CH_(3)COCH_(2)CH_(3)`. Thus, the structure of `[A], [B], [C]` and [D] and the corresponding reactions may be written as follows: