The amine shown is exhaustively methylated with excess $\mathrm{CH}{}_3\mathrm{I}$, treated with moist $\mathrm{Ag}{}_2\mathrm{O}$ and then heated. How many moles of $\mathrm{CH}{}_3\mathrm{I}$ are consumed per mole of the amine, and what is the major alkene?

The amine is butan-2-amine, a primary amine with two N-H bonds that become N-CH3 groups, and the resulting tertiary amine is quaternised by a third equivalent, giving the trimethylammonium iodide (3 mol). Hofmann elimination of the hydroxide then removes the more accessible hydrogen from the methyl group, giving but-1-ene as the major alkene.