(Butan-2-yl)trimethylammonium hydroxide, $\mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{CH}(\mathrm{CH}{}_3)-\mathrm{N}{}^{+}(\mathrm{CH}{}_3){}_3\mathrm{OH}{}^{-}$, is heated at about $180{}^{\circ }\mathrm{C}$. The major alkene is

Quaternary ammonium hydroxides undergo Hofmann elimination, which follows the Hofmann rule. The bulky $-\mathrm{N}(\mathrm{CH}{}_3){}_3{}^{+}$ group and the carbanion-like E2 transition state make the more acidic, less hindered primary hydrogens of the methyl group the ones removed. Hence the less substituted but-1-ene is the major product, not but-2-ene.