Acid catalysis

Acid catalysis is an increase in reaction rate caused by proton transfer from an acid catalyst. The proton transfer makes a reactant more reactive and the acid is regenerated during the catalytic cycle.

Brønsted–Lowry acid–base theory: A theory defining acids as proton donors and bases as proton acceptors. Acid catalysis proceeds through transfer of the acid’s proton to a reactant.
Chemical kinetics: The study of reaction rates and the factors that affect them. Acid catalysis is identified by a rate increase, not merely by an acidic medium.
Fischer esterification: An equilibrium reaction of a carboxylic acid and an alcohol that forms an ester and water. Acid protonates the carbonyl oxygen, making the ester-forming pathway faster.
Base catalysis: An increase in reaction rate caused by proton transfer to a base catalyst. It accelerates reactions through proton acceptance rather than acid-mediated proton donation.
Protonation: The addition of a proton to an atom, molecule, or ion. This is the elementary step that activates many substrates in acid-catalyzed reactions.
Activation energy: The energy barrier reactants must overcome to reach a reactive transition state. Proton transfer can open a pathway with a lower activation barrier.
Acid-catalyzed hydrolysis: Bond cleavage by water accelerated through proton transfer from an acid. Protonation makes a bond more susceptible to cleavage by water.
Lewis acid catalysis: Catalysis by an electron-pair acceptor that activates a substrate through coordination. Many Lewis acids activate reactants without transferring a proton.
Carbocation: An organic ion in which a carbon atom bears a positive charge. Protonation can generate carbocations that undergo rapid rearrangement or substitution.
Chemical equilibrium: A dynamic state in which forward and reverse reaction rates are equal. Catalysts change how quickly equilibrium is reached, not its position.

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