Chemoselectivity

Chemoselectivity is the preference of a reaction to occur at one functional group rather than another in the same molecule. It allows reactions to modify one reactive site while leaving other sites intact.

Reaction kinetics: The study of reaction rates and how they depend on conditions and mechanisms. Relative rates determine which competing functional group reacts first.
Functional group: A characteristic arrangement of atoms that gives an organic molecule a recognizable pattern of reactivity. Chemoselectivity compares competing functional groups within one molecule.
Orthogonal protection: A strategy using protecting groups removable under mutually compatible, distinct conditions. Orthogonal removal lets synthesis control which functional groups are exposed at each stage.
Regioselective reaction: A reaction that preferentially forms one constitutional isomer by selecting among possible reaction positions. It resolves positional competition, not competition between different functional groups.
Transition state: A high-energy molecular arrangement at the boundary between reactants and products. Different transition-state energies can make one functional group react preferentially.
Regioselectivity: The preference for forming one constitutional isomer over another when reaction can occur at multiple positions. It selects among positions, whereas chemoselectivity selects among functional groups.
Late-stage functionalization: The modification of a complex molecule near the end of its synthesis. Chemoselective reactions can edit one site without rebuilding the molecular framework.
Stereoselective reaction: A reaction that forms one stereoisomer preferentially over other possible stereoisomers. Its selectivity distinguishes spatial arrangements, not functional-group identities.
Catalysis: The acceleration of a chemical reaction by a substance regenerated during the process. Catalysts can alter relative reaction rates and redirect chemoselectivity.
Stereoselectivity: The preference for forming one stereoisomer over other possible stereoisomers in a reaction. It concerns three-dimensional products rather than which functional group reacts.

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