polysubstituted

Polysubstituted is a term used in chemistry to describe a molecule in which multiple substituent groups have replaced hydrogen atoms on a common parent framework. The term is relative: a compound is described as polysubstituted when it carries two or more substituents on the same core, such as an aromatic ring, an alkane chain, or a heterocycle.

Common context is polysubstituted benzene rings, where two or more substituents are attached to the six-membered ring (e.g., 1,2-dichlorobenzene, 1,3,5-trichlorobenzene). Similar ideas apply to other rings and to alkanes, where several hydrogen atoms are replaced by substituents, yielding polysubstituted alkanes or heterocycles. The positions of substituents are specified with locants in the name.

Polysubstitution affects properties and reactivity. Additional substituents change steric hindrance, melting and boiling points, and solubility. Electron-donating or electron-withdrawing groups alter electronic distribution, influencing reaction rates and selectivity. In electrophilic aromatic substitution, existing substituents can direct new substitutions and modify regioselectivity in complex ways, especially as the number and identity of substituents increase.

In nomenclature, substituents and their positions are included in the name of the compound, with numbers indicating their attachment points on the parent structure. The term is also used in polymer and coordination chemistry to describe multiple pendant groups on a backbone or metal center.