Final answer:
The cyanide anion, (-CN), acts as a nucleophile by donating a pair of electrons to a carbon atom with a partial positive charge in nucleophilic addition reactions. This results in the formation of a cyanohydrin, containing a carbon with a cyanide and hydroxyl group. The cyanide anion is a strong nucleophile due to its high electron density on the carbon atom.
Step-by-step explanation:
The cyanide anion (−CN) makes nucleophilic addition possible due to its ability to act as a nucleophile by donating a pair of electrons to a carbon atom with a partial positive charge. In nucleophilic addition reactions, the cyanide anion attacks the electrophilic carbon of a carbonyl compound (such as aldehydes or ketones) to form a new bond. This results in the formation of a cyanohydrin, which contains a carbon with a cyanide (-CN) and hydroxyl (-OH) group attached to it.
For example, when cyanide reacts with an aldehyde, it forms a cyanohydrin as shown in the following reaction:
RCHO + CN− → RCH(OH)CN
This nucleophilic addition is possible because the cyanide anion is a strong nucleophile, meaning it has a high electron density on the carbon atom. This electron-rich anion can attack the carbon atom of a carbonyl compound, which has a partial positive charge due to the electronegativity difference between carbon and oxygen.