Acetone (CH3COCH3) reacts with hydrogen cyanide (HCN) to form a cyanohydrin, which is an example of nucleophilic addition.

Nucleophilic addition reactions involve the attack of a nucleophile on an electrophile, resulting in the formation of a new bond. In this case, HCN acts as the nucleophile and acetone acts as the electrophile.

Explanation of the reaction:

1. Nucleophilic attack: The nucleophilic cyanide ion (CN-) attacks the electrophilic carbonyl carbon of acetone. The carbonyl carbon is partially positive due to the polarized C=O bond.

2. Formation of a tetrahedral intermediate: The nucleophilic attack leads to the formation of a tetrahedral intermediate. The oxygen of the carbonyl group has a partial negative charge and forms a bond with the carbon of the cyanide ion.

3. Proton transfer: A proton transfer occurs from the oxygen of the tetrahedral intermediate to the nitrogen of the cyanide ion. This results in the formation of a cyanohydrin intermediate, which contains a hydroxyl group (-OH) and a cyanide group (-CN) attached to the same carbon atom.

4. Rearrangement: The cyanohydrin intermediate may undergo rearrangement to form a more stable isomer. This rearrangement involves migration of a hydrogen atom from the hydroxyl group to the carbon atom adjacent to the carbonyl group.

5. Final product: The rearranged cyanohydrin is the final product of the reaction. It contains a hydroxyl group and a nitrile group (-CN) attached to the same carbon atom.

Overall, the reaction between acetone and HCN involves the addition of a cyanide ion to the carbonyl group of acetone, resulting in the formation of a cyanohydrin. This reaction is an example of nucleophilic addition, as a nucleophile (HCN) attacks an electrophile (acetone) to form a new bond.