Which type of reaction involves the introduction of a functional group while removing a leaving group?

The correct choice corresponds to a substitution reaction, which is characterized by the introduction of a new functional group while simultaneously removing a leaving group. In a substitution reaction, one functional group or atom in a compound is replaced by another. This process often occurs in organic compounds where an atom or group of atoms can be displaced by another atom or functional group.

To elaborate, during a substitution reaction, a nucleophile (which is often negatively charged or neutral and has a lone pair of electrons) attacks a positively polarized carbon atom that is bonded to the leaving group. As the nucleophile forms a bond with the carbon, the leaving group departs, completing the substitution process. This mechanism is commonly seen in reactions involving alkyl halides, where halide ions can be substituted by nucleophiles such as alcohols or amines.

The other types of reactions mentioned do not fit this specific definition. Addition reactions involve the addition of atoms or groups to a double or triple bond without the loss of any atoms. Elimination reactions involve the removal of a small molecule (like water or a halide) from larger molecules, resulting in the formation of multiple bonds. Condensation reactions involve the combination of two molecules with the loss of a small molecule, typically water, without