Chapter 10, Problem 10.50P

Interpretation Introduction

Interpretation:

The stereoisomer of $\text{3-bromobutan-2-ol}$ that, on heating in the presence of sodium hydroxide, will produce an optically inactive epoxide is to be drawn and named.

Concept introduction:

In the presence of a strong base such as sodium hydroxide, a haloalcohol undergoes an intramolecular ${\text{S}}_{\text{N}}\text{2}$ reaction to form an epoxide if the hydroxyl group and the halogen are on adjacent carbons. For an ${\text{S}}_{\text{N}}\text{2}$ mechanism, the hydroxyl group must be in a position to launch a backside attack on the carbon to which the halogen is attached. This means the $\text{HO}-\text{C}-\text{C}-\text{X}$ dihedral angle must be ${180}^{\text{o}}$.

If the two carbon atoms of the reactant that form the epoxide ring are chiral carbons and the epoxide formed must be optically inactive, it must have a plane of symmetry, provided there are no other chiral carbons in the substituents.