To determine the product formed when 3-methylcyclohexanone reacts with CH₃MgBr (a Grignard reagent) and is subsequently acidified, let's go through the steps of the reaction together:
1. Identify the starting compound: 3-methylcyclohexanone is a cyclohexanone ring with a methyl group attached to the third carbon atom.
2. Understand the Grignard reagent reaction: CH₃MgBr is a Grignard reagent, which adds a methyl group (CH₃) to the carbonyl carbon of 3-methylcyclohexanone. This reaction forms a temporary intermediate:
- The carbonyl group (C=O) in 3-methylcyclohexanone is electrophilic. The CH₃ group from CH₃MgBr, acting as a nucleophile, attacks the electrophilic carbon of the carbonyl group.
- This nucleophilic attack leads to the formation of a tertiary alcohol intermediate where the carbonyl oxygen now bears a negative charge (alkoxide ion).
3. Acidification: After the addition of the CH₃MgBr to the carbonyl carbon, the reaction mixture is typically acidified in a second step. During acidification, the alkoxide ion picks up a proton (H⁺) from the acidic medium to form the final alcohol.
4. Product Formation:
- The methyl group that was initially attached to the carbonyl carbon remains attached.
- The original 3-methyl substituent and the newly added methyl group (from CH₃MgBr) are now both attached to the former carbonyl carbon.
- Consequently, the product is a cyclohexanol ring with two methyl groups attached to the same carbon, which is now the third position in the cyclohexanol ring. This is structurally known as 3,3-dimethylcyclohexanol.
Thus, the product formed is 3,3-dimethylcyclohexanol.
Among the given options:
1. 1,3-dimethylcyclohexanol
2. 1,4-dimethylcyclohexanol
3. 1-methylcyclohexanol
4. 4-methylcyclohexanol
The correct answer is 1,3-dimethylcyclohexanol.
