Question

If A, B, and C are the major products of their respective reactions then ‘C’ is

1.
2.
3.
4.

Answer 1

Ring expansion is a type of rearrangement and a special type of rearrangement of the carbocation. It is a process in which the ring gets expanded. For a ring expansion to take place, below are the conditions that need to be satisfied:
1.The ring needs to be three, four, or five numbered
2.Carbocation should be attached to the atom directly attached to the ring.

Complete step by step answer:
To solve the given question, we will utilise the concept of ring expansion. Let's start with the given compound.

Due to mesomeric effect, the above compound can be shown as:

Now when it reacts with dil. $H_2SO_4$, with this compound,then sulfonation occur and we get the compound A and the sulfonation reactions is shown as below:

Hence the compound A formed is 1,3-dimethylcyclohexane-1,3-diyl bis(hydrogen sulphate). Now when this compound reacts with $SOCl_2$, the associated reaction is given below:

The product obtained is 1,3-dichloro-1,3-dimethylcyclohexane and is compound B. Now when this compound reacts with Alcoholic $KOH$, the associated reaction is given below:

The product we get is 1,3-dimethycyclohexane-1-3-diol and the final product obtained is:

So, the correct answer is Option D.

Note: As we know in the case of ring expansion and contraction of an existing ring, we often tend to prepare the structures that are difficult to prepare using a single cyclization reaction which has a slow rate of formation as in the case of a ring involving seven or more members. The ring expansion can be classified under various categories based on the mechanism of reaction and atoms incorporated.