monoprotiset

Monoprotiset is a term used in chemistry to describe a chemical species that can donate or release exactly one proton (H+) in an acid–base reaction. The concept is most commonly applied to monoprotic acids, which dissociate in water by releasing a single proton, in contrast to polyprotic acids that can donate two or more protons.

A monoprotiset is defined by having a single ionizable proton under typical conditions. This leads to a single dissociation step and, in titration experiments, one distinct equivalence point. Its acidity is characterized by a pKa value, which reflects the equilibrium between the neutral molecule and its conjugate base. Strong monoprotic acids dissociate almost completely in water (for example, hydrochloric acid), while weak monoprotic acids dissociate only partially (for example, acetic acid or formic acid).

Examples commonly cited as monoprotic acids include hydrochloric acid (HCl), formic acid (HCOOH), and acetic acid (CH3CO2H). While bases are discussed separately, a conjugate base formed after the loss of the sole proton from a monoprotic acid is also described within the same framework of monoprotiset chemistry.

Applications of the monoprotiset concept appear in routine acid–base chemistry, buffer solution design, and pH calculations. When appropriate, calculations often assume a monoprotic model, using the Henderson–Hasselbalch equation to relate pH, pKa, and the ratio of conjugate base to weak acid.

See also: monoprotic acid, polyprotic acid, titration, pKa.