Question

The structure of Q in the following reaction scheme is.

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is B

To determine the structure of compound Q in the reaction scheme, we need to analyze the given reaction and understand the role of the reagents. 

• Starting with the compound \(M\) (an enantiopure sugar) which has the following structure:

• The reagent used here is \(\text{PhNHNH}_2\) in excess. This reagent is commonly used in the Wolff-Kishner reduction, which reduces aldehydes and ketones to hydrocarbons.
• In the first step, the carbonyl group (CHO) in \(M\) is expected to react with the \(\text{PhNHNH}_2\) excess to form an intermediate hydrazone (N). This results in the removal of the oxygen and creation of a double bond with nitrogen.
• The intermediate hydrazone \(N\) then further reacts to eliminate nitrogen, reducing the carbonyl to a methylene group (CH₂), resulting in compound \(P\), which is an alkane.
• The structure of compound Q would therefore have the hydroxyl groups intact but the aldehyde group reduced to a CH₂ group.
• The correct representation of Q is thus the structure with the CHO group replaced by CH₂. Among the options, the correct one corresponds with the following structure:

Therefore, the structure of Q is where the CHO group has been reduced to CH₂, preserving the enantiopurity and positions of hydroxyl groups.