Chemistry - Halogen Derivative Question with Solution | TestHub

Question Explanation:

Determine the major product of an elimination reaction with a bulky base.

Concept:

Hofmann Elimination via ${\mathrm{E}}_2$ Mechanism.

Solution:

The reaction involves a secondary alkyl bromide reacting with a very bulky base (Sodium 3-ethylpentan-3-olate). Due to significant steric hindrance, the bulky base cannot easily access the more substituted $\beta$-hydrogen to form the stable Zaitsev product.

Instead, it abstracts the most accessible (least hindered) $\beta$-hydrogen from the terminal methyl group.

This leads to the formation of the Hofmann product (the less substituted alkene) as the major product.

Path A (Zaitsev): Removing H from the CH group attached to the ring (more hindered).

Path B (Hofmann): Removing H from the terminal −CH₃ group (less hindered).

Result: Terminal alkene (Vinylcyclohexane) is formed.