Final answer:
The nucleophilic site is the part of a molecule where a nucleophile attacks and forms a new covalent bond.
Step-by-step explanation:
The nucleophilic site is the part of a molecule where a nucleophile attacks and forms a new covalent bond. In the compound H₂C-O-CH₃, the nucleophilic site is the oxygen atom. In IH₂C=CH₂, the nucleophilic site is the carbon atom in the double bond. In CH₃NH₂, the nucleophilic site is the nitrogen atom.