Question

The process(es) and/or intermediate(s) through which the following transformation proceeds is/are 

• A. 1,2-methide shift
• B. 1,3-methide shift
• C. non-classical carbocation
• D. tertiary carbocation

Hint:

Acid-catalyzed reactions involving carbocation intermediates are prone to rearrangements (1,2-shifts of alkyl or hydride groups) to form more stable carbocations. In systems with significant steric congestion or the possibility of charge delocalization through bridging interactions, non-classical carbocations can play a role in the reaction pathway. Always consider the stability of the carbocation intermediates and the possible rearrangement pathways.

Answer 1

The Correct Option is A, C, D

Step 4: Deprotonation to Form the Alcohol
The intermediate loses a proton to form the final neutral alcohol product. The observed regioselectivity in the final product confirms that rearrangement has occurred.

Conclusion:
The reaction proceeds through:

• Initial tertiary carbocation (D)
• 1,2-methyl shift (A) to a more stable rearranged carbocation
• Possibly via a non-classical intermediate (C)

A 1,3-methide shift (structure B) is unlikely due to its higher energy barrier.