What type of reaction involves the replacement of a functional group in a compound?

The type of reaction that involves the replacement of a functional group in a compound is a substitution reaction. In a substitution reaction, one functional group is replaced by another, resulting in a new compound with different properties. This process typically occurs when a reactant, often a nucleophile, replaces a leaving group in a molecule, allowing the overall structure to change while maintaining the core framework of the compound.

For instance, in the case of alkanes, a halogen might substitute for a hydrogen atom, forming a haloalkane. This is integral in organic chemistry reactions where one functional group can change the reactivity and characteristics of a molecule. Thus, the ability to manipulate and substitute functional groups is a key concept in organic synthesis and design.