Question

Why can’t 1-methylcyclohexanol be prepared from a carbonyl compound by reduction?

Short answer

Answer

In 1-methyl cyclohexanol, tertiary alcohol is present, hence it can’t be reduced from any carbonyl compound.

Step-by-step solution

Step-by-Step Solution Step 1: Function of metal hydrides

Metal hydrides such as sodium borohydride and lithium aluminium hydride are strong reducing agents that can reduce an aldehyde into primary alcohol and a ketone into secondary alcohol.

These are as shown below:

Structure of 1-methylcyclohexanol

The structure of 1-methylcyclohexanol has a tertiary alcoholic group, which is shown below:

Observation of the structure

The structure contains a tertiary alcohol group where no $\mathrm{\alpha }$-hydrogen is present. Hence, it cannot be reduced by any carbonyl group, as the valency of the carbonyl group exceeds its valency of 4.

Based on the explanations, in the case of 1-methyl cyclohexanol, tertiary alcohol is present. Hence, it can’t be reduced from any carbonyl compound.