QNEET-2023-Ch-210: NEET 2023 Chemistry - Class 12 NEET-2023-Ch-210 Solution: Consider the following reaction and identify the product :…

This problem is a classic demonstration of carbocation rearrangement during an $\text{S}_{\text{N}}1$ nucleophilic substitution: 1. Protonation: The lone pair on the oxygen atom of the secondary alcohol (-OH) attacks the H_ from HBr, turning it into an excellent leaving group (-OH__). 2. Carbocation Formation: The water molecule leaves, generating a Secondary (2�) Carbocation on Carbon-2: $\text{CH}_{3}-\overset{+}{\text{C}}\text{H}-\text{CH}(\text{CH}_{3})_{2}$ 3. 1,2-Hydride Shift: The adjacent Carbon-3 holds a hydrogen atom and is a tertiary carbon. To attain greater thermodynamic stability, the hydrogen atom shifts with its electron pair (a hydride shift) to Carbon-2. This transforms the unstable secondary carbocation into a highly stable Tertiary (3�) Carbocation: $\text{CH}_{3}-\text{CH}_{2}-\overset{+}{\text{C}}(\text{CH}_{3})_{2}$ 4. Nucleophilic Attack: The remaining bromide ion (Br_) attacks this stable tertiary carbocation center, yielding the major final product: 2-Bromo-2-methylbutane.