Depotasjon

Depotasjon, also called deprotonation, is the chemical process in which a molecule or ion loses a proton (H+). In Brønsted–Lowry acid–base theory, it converts an acid into its conjugate base, and the reverse process is protonation. The occurrence of depotasjon depends on the acidity of the hydrogen atom, the strength of the base present, and the solvent.

Most common sites for depotasjon are acidic hydrogen atoms such as those on carboxylic acids (R-COOH), phenols, alcohols, and thiols. A strong base can deprotonate less acidic species as well, for example generating alkoxide ions from alcohols or enolate ions from carbonyl compounds. Ammonium, for instance, can be deprotonated to produce amines. The ease of depotasjon is largely governed by the pKa of the proton and the stabilization of the conjugate base by resonance, inductive effects, or solvation.

In solution, depotasjon is an equilibrium: a weaker acid or stronger conjugate base shifts the balance toward the deprotonated form. The Henderson–Hasselbalch equation is often used to relate pH, pKa, and the ratio of deprotonated to protonated species, which is central to buffer design and pH control in chemistry and biology.

Applications include the generation of nucleophiles for organic synthesis (for example, deprotonation of acetic acid with sodium hydroxide to give acetate; deprotonation of alcohols with strong bases to form alkoxides; formation of enolates from carbonyl compounds). In biochemistry, the protonation state of molecules like amino acids depends on pH and influences structure and activity.

See also: acid–base reactions, conjugate bases, pKa, buffers, enolates.