Question

Consider the following reaction:

The CORRECT pathway(s) involved in the reaction is/are

• A. E2 followed by isomerization
• B. E1 followed by isomerization
• C. Sn1 followed by isomerization
• D. Isomerization through carbocation

Hint:

In E1 reactions, carbocations are formed as intermediates. These can rearrange to form the most stable product. The E1 mechanism is often promoted by acids like sulfuric acid.

Answer 1

The Correct Option is B, D

Step 1: Understanding the reaction.
In the given reaction, a phenyl alcohol undergoes dehydration in the presence of sulfuric acid, resulting in an alkene. The major and minor products suggest the formation of a double bond in an electrophilic elimination process. The mechanism for such a reaction can be either E1 or E2, depending on the stability of the intermediate carbocation.
Step 2: Analyzing the options.
- (A) E2 followed by isomerization: The E2 mechanism requires a strong base and simultaneous removal of a proton and leaving group. However, the reaction involves sulfuric acid, which promotes carbocation formation, not an E2 mechanism. Thus, this option is not correct. - (B) E1 followed by isomerization: In the E1 mechanism, the first step involves the formation of a carbocation intermediate, followed by the elimination of a proton to form the double bond. The carbocation can rearrange, leading to the formation of the major and minor products. This matches the given reaction, making this the correct choice. - (C) Sn1 followed by isomerization: The reaction does not involve substitution, so this option is incorrect. - (D) Isomerization through carbocation: The formation of a carbocation intermediate in the E1 mechanism allows the possibility of isomerization, which results in the major and minor products observed. This is the correct description of the reaction pathway.

Step 3: Conclusion.
The correct answers are (B) and (D) because the reaction proceeds via an E1 mechanism, with the formation and isomerization of a carbocation intermediate.