Question

p-Chlorotoluene is the major product in which of the following reactions?

• A. I, III only
• B. I, II only
• C. II, III only
• D. I, II, III

Hint:

Electrophilic substitution (e.g., Cl$_2$/FeCl$_3$) and Sandmeyer reactions target the aromatic ring; free radical chlorination (Cl$_2$/hv) attacks alkyl side chains.

Answer 1

The Correct Option is C

To solve the problem, we need to identify in which reactions p-Chlorotoluene is the major product. The question involves three reactions with different reagents and conditions.

1. Understanding the Concepts:

- Reaction I: Chlorination of toluene with Cl₂ under UV light is a free-radical halogenation process. In this reaction, p-Chlorotoluene is typically the major product due to the favorable position for chlorination at the para position relative to the methyl group.

- Reaction II: Chlorination of toluene with Cl₂ under dark conditions with iron (Fe) as a catalyst is also a free-radical halogenation, leading to a mix of products. The para position is favored, but there can also be some ortho substitution.

- Reaction III: In this reaction, an amine group undergoes diazotization followed by chlorination. This process leads to the formation of p-Chlorotoluene as the major product due to the electron-donating effect of the methyl group and the electron-withdrawing nature of the nitro group.

2. Given Values:

The reactions under consideration are:

• I) Chlorination of Toluene with Cl₂ under UV light
• II) Chlorination of Toluene with Cl₂ in the presence of Fe and dark conditions
• III) Diazotization of Aniline and subsequent chlorination

3. Analyzing the Options:

1. I, III only: Reaction I produces p-Chlorotoluene, and Reaction III also leads to p-Chlorotoluene, so this is correct.

2. I, II only: While Reaction I produces p-Chlorotoluene, Reaction II can lead to a mixture of products, with some ortho-substitution, so it is not the major product in this reaction.

3. II, III only: Reaction II produces a mixture of products, and Reaction III produces p-Chlorotoluene, so this is the correct answer.

4. I, II, III: Reaction II produces a mixture of products, so this option is not the most accurate.

Final Answer:

The major product, p-Chlorotoluene, is formed in reactions II and III only (Option C).