Protongivare

Protongivare, Swedish for "proton donor," is a chemical concept in acid–base chemistry. It refers to a substance that donates a proton (H+) to another molecule or ion in an acid–base reaction, according to the Brønsted–Lowry theory. In such reactions, the donor becomes the conjugate base of the resulting acid. By contrast, the species that accepts the proton is called a base. The concept emphasizes proton transfer rather than electron-pair sharing, distinguishing Brønsted–Lowry acids from Lewis acids.

In aqueous solution, common protongivare include mineral acids such as hydrochloric acid (HCl) and sulfuric acid (H2SO4), as well as weaker organic acids like acetic acid (CH3COOH). When HCl donates a proton to water, it forms Cl− and the hydronium ion H3O+. The strength of a protongivare is described by its acid dissociation constant Ka or its pKa: smaller pKa means stronger protongivare.

In biological systems, pH-dependent proton donation and acceptance drive many processes, including enzyme catalysis and metabolic pathways. Some molecules can act as protongivare in one context and as bases in another, depending on pH and the reacting partner.

Limitations: protongivare is defined within the Brønsted–Lowry framework; other acid–base theories, such as Lewis acid–base theory, describe proton donation differently. See also Brønsted–Lowry acid, conjugate base, pKa.