BronstedLowryn

Bronsted-Lowry theory is a conceptual framework in chemistry named after Johannes Nicolaus Brønsted and Thomas Martin Lowry. Proposed in 1923, it defines acids as substances that donate protons (H+) and bases as substances that accept protons. This definition extends acid-base chemistry beyond aqueous environments and applies to a wide range of solvents and reactions.

A central idea is proton transfer: in a Bronsted-Lowry reaction, an acid donates a proton to a base, producing a conjugate base of the original acid and a conjugate acid of the original base. The pair of species involved before and after the transfer are known as a conjugate acid-base pair. For example, in HCl reacting with NH3, HCl donates a proton to NH3, yielding NH4+ and Cl-.

The theory emphasizes the role of the solvent and the concept of conjugates. In water, for instance, acid-base reactions often involve hydronium ions (H3O+). In nonaqueous solvents, the same definitions apply with the solvent acting as the base or acid, respectively, altering the ease of proton transfer.

Strengths and limitations accompany the theory. Acid strength is related to the tendency to donate a proton (quantified by Ka and pKa), while base strength concerns the tendency to accept a proton. A stronger acid has a weaker conjugate base. The Bronsted-Lowry framework complements the Arrhenius model and is compatible with Lewis theory, in that every Bronsted-Lowry acid/base is a Lewis acid/base, though the converse is not always true.

Applications include buffer solutions, organic synthesis, and biochemistry, where proton transfers govern many reactions and equilibria.