Question

Which of the followings is most reactive towards addition reaction of hydrogen cyanide to form corresponding cyanohydrin?

• A. Acetone
• B. Formaldehyde
• C. Acetaldehyde
• D. Diethyl ketone

Answer 1

The correct option is B Formaldehyde

Formaldehyde is most reactive towards addition reaction of hydrogen cyanide to form corresponding cyanohydrin. Carbonyl C atom in formaldehyde is most electrophilic. In aldehydes and ketones, $+I$ effect of alkyl groups decreases electrophilic character of carbonyl C atom. Lower is the electrophilic character, lower is the reactivity towards addition reaction of hydrogen cyanide to form corresponding cyanohydrin.