Question

The major aromatic product C in the following reaction sequence will be:

(1)

(2)

(3)

(4)

Answer 1

Hint: HBr is an example of an inorganic compound. HBr and its aqueous solution are useful as a reagent in the preparation of bromine compounds. HBr, when undergoing reaction with an alkene, forms a complex of alkyl bromide. HBr undergoes a reaction with alcohol to give an alkyl bromide as a product.

Complete Step by Step Solution:
The reaction of ketone with HBr in excess results in the breaking of the bond. The reaction is as follows:

Image: Reaction of ketone with HBr

As the HBr is in excess, so, the bromination at the o and p position takes place.
The next step is the reaction of A with alcoholic potassium hydroxide in presence of acid. The reaction of an alkyl halide in alcoholic potassium hydroxide results in the removal of halogen acid to form an alkene.
So, the reaction is,


Image: Reaction of A with alcoholic potassium hydroxide in presence of acid

The next step is the reaction of B with Ozone in the presence of acid.
Image: Reaction of B with Ozone in presence of acid

This is an ozonolysis reaction. Ozonolysis is a reaction in organic chemistry where the breaking of double or triple bonds of alkynes, alkenes or azo compounds takes place in reaction with ozone. Alkynes and alkenes form organic compounds where the replacement of multiple carbon-carbon bonds takes place by a carbonyl group whereas azo compounds give nitrosamines.

Hence, the product C is in option C.

Note: Students often get confused between the reaction of an alkyl halide with aqueous and alcoholic KOH. It is to be noted that the reaction of an alkyl halide with alcoholic KOH gives alkene as a product. But, when alkyl halide undergoes a reaction with aqueous KOH, it gives alcohol as a product.