Question

${CH}_3{CH}_{2}CO{CH}_2{CH}_3$ reacts with hydrogen cyanide to form an organic product called a cyanohydrin.
Which statement is correct?

• A. The cyanohydrin product has one chiral centre
• B. The cyanohydrin product is formed by electrophilic addition
• C. The cyanohydrin product is formed via an intermediate which contains a $C-OH$ group.
• D. The formation of the cyanohydrin product requires the use of cyanide ions as a catalyst

Answer 1

The correct option is D The formation of the cyanohydrin product requires the use of cyanide ions as a catalyst

The atoms of HCN add to the carbon-oxygen double bond of the ketone by nucleophilic attack of the cyanide anion on the electrophilic carbon of the carbonyl.

As electronegativity of C is less than O ,C will have + charge and O - charge

same is with CN where N is more electronegative than C

For successful cyanohydrin formation it is important to have free cyanide ions available to react with the ketone or aldehyde. This can be achieved by using a salt (e.g. KCN or NaCN) or a silylated (e.g. Me3SiCN) form of cyanide under acidic conditions or by using HCN with some base added to produce the needed CN− nucleophile.