KCET 2026 Chemistry Solved Paper

Concept:Nucleophilic addition reactions of carbonyl compounds give different products depending on the reagent used.Explanation:Hydroxylamine ($\mathrm{NH}_{2}\mathrm{OH}$) reacts with aldehydes or ketones to form oximes.$R_{2}C=O + \mathrm{NH}_{2}\mathrm{OH} \rightarrow R_{2}C=NOH$Therefore, (a) matches with (ii).Primary amines ($R-\mathrm{NH}_{2}$) form imines, commonly called Schiff bases, with carbonyl compounds.$R_{2}C=O + R'\mathrm{NH}_{2} \rightarrow R_{2}C=NR'$Therefore, (b) matches with (iii).Alcohols ($R-\mathrm{OH}$) convert aldehydes or ketones into acetals in the presence of an acid.Therefore, (c) matches with (iv).Hydrogen cyanide ($H-C\equiv N$ or HCN) adds across the carbonyl group to give cyanohydrins.$R_{2}C=O + HCN \rightarrow R_{2}C(OH)CN$Therefore, (d) matches with (i).Hence the correct matching is $a-ii,\ b-iii,\ c-iv,\ d-i$.Answer:Option A: $a-ii,\ b-iii,\ c-iv,\ d-i$