Question

Product of the following reaction is

• A.
• B.
• C.
• D.

Hint:

When performing reactions with mercury salts and sodium borohydride, look out for the formation of cyclic compounds from the initial alcohols and alkenes.

Answer 1

The Correct Option is B

This reaction describes a two-step transformation where an alkene is converted to a cyclic compound through hydroxyl addition and subsequent ring closure.

Reaction Mechanism:

1. Hydroxyl Addition:
The hydroxyl group ($\text{OH}$) adds to the most substituted carbon of the alkene double bond, following Markovnikov's rule. This regioselectivity occurs because:
- The more substituted carbon stabilizes the partial positive charge in the transition state
- The resulting carbocation intermediate is more stable at the more substituted position

2. Ring Formation:
The added hydroxyl group then participates in an intramolecular reaction:
- The oxygen's lone pair attacks an electrophilic carbon center in the same molecule
- This nucleophilic substitution results in water elimination ($\text{H}_2\text{O}$)
- Simultaneous formation of a new carbon-oxygen bond creates the cyclic structure

Key Features:
- Regioselectivity: OH always adds to the more substituted carbon
- Stereochemistry: The reaction typically proceeds with anti-addition
- Driving Force: Ring formation provides thermodynamic stability

Final Product:
The transformation yields a cyclic ether (if forming C-O bond) or alcohol (if forming C-C bond), with the ring size determined by the original molecule's structure.

Answer 2

Addition of OH at most substituted side of the ene and final product is formed by loss of H+ resulting in the formation of ring.