Question

A carbonyl compound P, which gives positive iodoform test, undergoes reaction with $C{H}_{3}MgBr$, followed by dehydration to give an olefin Q. The ozonolysis of Q gives rise to a dicarbonyl compound R, which undergoes intramolecular aldol condensation reaction to predominantly give S.
The structure of the carbonyl compound P is:
$$P\underset{\begin{array}{c}2.H{}^{+},H_{2}O\\ 3.H_{2}S{O}_4,\mathrm{\Delta }\end{array}}{\overset{1.MeMgBr}{\to }}Q\underset{2.Zn,H_{2}O}{\overset{1.O_3}{\to }}R\underset{2.\mathrm{\Delta }}{\overset{1.O{H}^{-}}{\to }}S$$
A.

B.

C.

D.

Answer 1

Hint: Methyl ketones respond to iodoform test and form respective carboxylic acid and iodoform as the products. It is a test used to find the presence of methyl ketones in the given compounds. Generally methyl ketones react with Grignard reagent and form respective alcohols as the products.

Complete answer:
- In the question it is mentioned that the compound-P gives Iodoform test, means compound-P must be a methyl ketone. Then from the given options P will be either A or B, because Option A and B only contains methyl ketones in their structure.
- Now by taking structures from option A and option B we will proceed and write the products formed as per the question. Later will decide which option will be correct.
- If we are going to take Option A as P the following reaction takes place.

- If we are going to take Option B as P the following reaction takes place.

- But compound ‘R’ undergoes intramolecular aldol condensation and forms a cyclic compound (S), it only happens if we consider compound P is Option B.
- If we take compound P is option B, then in intermolecular aldol condensation it won’t form a cyclic compound (S)

Therefore the compound P is option B.

Note:
If we are going to take option A is compound P then the compound R formed as an intermediate product undergo intramolecular Cannizaro reaction and forms a carboxylic group and an alcohol in compound S. but in the question it is clearly mentioned the compound R undergoes intramolecular aldol condensation reaction means the Compound P is option B only.