Butan-2-amine is treated with excess CH3I to give the quaternary ammonium iodide, which is converted by moist Ag2O into the hydroxide and then heated (Hofmann elimination). The major alkene and the number of moles of CH3I consumed per mole of amine are

JEE Advanced levelSingle correct optionDifficulty 3 of 3o4036

Butan-2-amine is treated with excess $CH X_{3} I$ to give the quaternary ammonium iodide, which is converted by moist $Ag X_{2} O$ into the hydroxide and then heated (Hofmann elimination). The major alkene and the number of moles of $CH X_{3} I$ consumed per mole of amine are

A primary amine needs three methylations to reach

R - N X^{+} (CH X_{3}) X_{3}

, so 3 mol of

CH X_{3} I

are used. On heating the hydroxide undergoes E2 with the very bulky

N (CH X_{3}) X_{3}

leaving group, and hydroxide removes the more accessible, more acidic hydrogen from the CH3 group, so the Hofmann product but-1-ene predominates.