Brønsted

Brønsted is a Danish surname, most widely recognized in chemistry through Johannes Nicolaus Brønsted. Along with Thomas Martin Lowry, Brønsted co-developed the Brønsted–Lowry acid–base theory in the early 20th century, articulated in 1923. The theory provides a proton-transfer perspective on acid-base reactions that extends beyond the aqueous environments emphasized by earlier definitions.

In Brønsted–Lowry terms, an acid is a substance that donates a proton, while a base is a substance that accepts a proton. During a reaction, the donating species forms its conjugate base, and the accepting species forms its conjugate acid. This framework allows acid-base concepts to apply in many solvents and contexts where water is not the medium, making it more general than the Arrhenius definition. The notion of conjugate acid–base pairs and the use of proton transfer to describe reactivity are central to this theory.

Common examples illustrate the concept: acetic acid (CH3COOH) donates a proton to water, giving CH3COO− and H3O+. Ammonia (NH3) acts as a base, accepting a proton from water to form NH4+ and OH−. These ideas underpin a vast range of chemical processes, including organic reactions, enzyme catalysis, and biochemical pathways, where proton transfer governs reaction mechanisms and molecular interactions.

Brønsted’s contribution remains foundational in chemistry education and research, shaping how scientists analyze acidity, basicity, and proton-transfer dynamics across disciplines.