Chapter 10, Problem 10.25P

Interpretation Introduction

Interpretation:

The complete mechanism for the given reactions is to be drawn, and the major product is to be predicted.

Concept introduction:

Under neutral or basic conditions, a nucleophile attacks an epoxide at the less highly alkyl-substituted C atom of the ring, from the side opposite the O atom.

Under acidic conditions, a nucleophile attacks an epoxide at the more highly alkyl-substituted carbon. The C-O bonds in an epoxide partially break as a result of protonation, lengthening the C-O bonds. As a result, more positive charge develops at the more hindered side.

The ${\text{S}}_{\text{N}}\text{2}$ reaction proceeds faster at carbon with less steric hindrance. The strong nucleophile attacks from backside, and the substituents remain bonded to the carbon atom.