acidcatalyzed

Acid-catalyzed reactions are chemical reactions whose rate is increased by an acid catalyst. They can be driven by Brønsted acids, which donate protons, or by Lewis acids, which accept electron pairs. In Brønsted acid catalysis, protonation of a functional group makes it more electrophilic or conducive to leaving group departure, often forming carbocation or oxonium ion intermediates. In Lewis acid catalysis, coordination to a substrate increases electrophilicity and facilitates bond formation or cleavage.

Common categories include hydrolysis, dehydration, and condensation reactions. Examples include hydrolysis of esters and amides under acidic conditions, conversion of alcohols to alkenes by dehydration, and formation of acetals and ketals from carbonyl compounds and alcohols. Other well-known processes involve rearrangements such as the Wagner-Meerwein or pinacol rearrangements and electrophilic aromatic substitutions mediated by Lewis or Bronsted acids.

Catalysts range from traditional mineral acids like sulfuric or hydrochloric acid to Lewis acids such as AlCl3 or BF3, and to solid acid catalysts including sulfonic-acid resins, sulfated zirconia, and zeolites. Heterogeneous solid acids offer easier separation and reuse in some settings, while homogeneous acids can provide higher activity for certain substrates. Disadvantages include corrosivity, potential for side reactions, and catalyst deactivation.

Applications span organic synthesis, polymer chemistry, and biomass processing, as well as pharmaceutical manufacturing. Understanding the mechanism and selectivity of acid-catalyzed steps helps chemists optimize reaction conditions, improve yields, and minimize undesired byproducts.