Chapter 10, Problem 10.63P

Interpretation Introduction

Interpretation:

A complete, detailed mechanism is to be drawn for the given reaction.

Concept introduction:

Alkyl amines with a $\text{β-hydrogen}$ undergo an elimination reaction when treated with excess iodomethane followed by silver oxide and heating. Unlike most elimination reactions, this reaction gives the least substituted alkene, an anti-Zaitsev product. The reaction is called Hofmann elimination.

The Amine functional group is alkylated to a quaternary ammonium ion, converting it into a bulky and good leaving group. If there are two hydrogens in $\text{β}$ positions, then the one that gives the less substituted alkene is eliminated. This is because the leaving group is bulky, and the $\text{β-hydrogen}$ on the less substituted carbon is in an anti-position in the most stable conformer. Formation of a more substituted alkene would generally require a less stable gauche conformer.