ProtonierungDeprotonierung

Protonierung and Deprotonierung are terms used in chemistry to describe the gain or loss of a proton (H+) by a molecule, ion, or functional group. In Brønsted–Lowry acid–base theory, proton transfers involve acids donating protons and bases accepting them. Protonierung refers to the formation of a conjugate acid by adding a proton, while Deprotonierung refers to the formation of a conjugate base by removing a proton.

The direction and extent of proton transfer depend on factors such as pH, pKa values, solvent, and temperature. Protonation typically occurs at heteroatoms with lone pairs (such as nitrogen, oxygen, or sulfur) or at carbonyl groups, where the resulting conjugate acid is sufficiently stable. Deprotonation occurs at acidic protons, including those in carboxylic acids, phenols, alcohols, and amines under appropriate pH conditions. The equilibrium between protonated and deprotonated forms is governed by the relative strengths of the acids and bases involved.

Mechanistically, proton transfers can be concerted or stepwise and are often facilitated by solvent networks, especially in water, where hydrogen bonding and solvent polarity influence rates and equilibria. In nonpolar solvents or gas phase, proton transfers may require catalysts or highly acidic conditions.

Applications and relevance are wide: in biochemistry, pH-dependent activity and enzyme catalysis rely on protonation states; in organic and inorganic synthesis, controlling protonation/deprotonation guides reactivity and selectivity; in analytical chemistry, buffers modulate experimental conditions; in materials science, proton conduction and proton-coupled processes depend on these equilibria.