Question

What is the ratio of sp$^3$ carbons to sp$^2$ carbons in the product 'P' of the given sequence of reactions?

• A. 3 : 1
• B. 2 : 1
• C. 1 : 2
• D. 1 : 3

Hint:

Count sp$^3$ (tetrahedral, single bonds) and sp$^2$ (trigonal planar, double bonds or aromatic) carbons carefully. Clemmensen reduction converts ketones to alkanes, increasing sp$^3$ carbons.

Answer 1

The Correct Option is D

To solve the problem, we need to determine the ratio of sp³ carbons to sp² carbons in the product 'P' after the given sequence of reactions.

1. Understanding the Concepts:

- Reaction 1 (Formation of Q): The first reaction involves the halogenation of a methyl group on a benzene ring, followed by the reaction with aluminum chloride (AlCl₃) under anhydrous conditions, which leads to an alkylation reaction. The carbon attached to the benzene ring (sp² carbon) remains unchanged, and the alkyl group is introduced to the ring. Thus, the reaction introduces sp³ carbons in the form of an alkyl group on the ring.

- Reaction 2 (Formation of P): The second reaction involves the reduction of the carbonyl group (C=O) using Zn-Hg (Clemmensen reduction). This reduces the carbonyl to a CH₂ group, converting the sp² carbon of the carbonyl group to an sp³ carbon.

2. Given Values:

The given reactions involve:

• Alkylation of a benzene ring (sp² carbon) followed by a reduction (sp² to sp³ conversion).
• The final product involves a combination of sp² and sp³ carbons.

3. Analyzing the Reaction Steps:

In the final product 'P', the alkyl group introduces additional sp³ carbons. The reduction step (Clemmensen reduction) converts the sp² carbonyl carbon into an sp³ carbon. Therefore, there is an increase in the number of sp³ carbons relative to the sp² carbons.

Final Answer:

The ratio of sp³ carbons to sp² carbons in the product 'P' is 1 : 3 (Option 4).