Acetaldehyde is treated in sequence with (i) HCN, trace KCN; (ii) LiAlH4 in dry ether; (iii) dilute H3O+ work-up. The product is

JEE Advanced levelSingle correct optionDifficulty 3 of 3o1148

Acetaldehyde is treated in sequence with (i) $HCN$ , trace $KCN$ ; (ii) $LiAlH X_{4}$ in dry ether; (iii) dilute $H X_{3} O X^{+}$ work-up. The product is

Step (i) gives

CH X_{3} - CH (OH) - CN

LiAlH X_{4}

reduces the nitrile to a primary amine

- CH X_{2} NH X_{2}

and does not touch the OH. The result is

CH X_{3} - CH (OH) - CH X_{2} - NH X_{2}

, 1-aminopropan-2-ol. The carbon chain is unchanged by the reduction.