Addition of HCN -Nucleophilic addition reaction

Overall Reaction:

$$\text{R--CO--R'} + \text{HCN} \xrightarrow{\text{OH}^- \text{ (pH 9--10)}} \text{R--C(OH)(CN)--R'} \quad (\text{Cyanohydrin})$$

Concept: The addition is initiated by a base catalyst which deprotonates weak acid $$\text{HCN}$$ to generate a highly reactive, free nucleophile. This nucleophile then directly attacks the electrophilic carbonyl carbon center.