Protonation

Addition of a proton to an atom, molecule, or ion, forming the conjugate acid

In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), usually denoted by H+, to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brønsted–Lowry acid, is deprotonation.) Some examples include The protonation of water by sulfuric acid: H2SO4 + H2O ⇌ H3O+ + HSO−4 The protonation of isobutene in the formation of a carbocation: (CH3)2C=CH2 + HBF4 ⇌ (CH3)3C+ + BF−4 The protonation of ammonia in the formation of ammonium chloride from ammonia and hydrogen chloride: NH3(g) + HCl(g) → NH4Cl(s) Protonation is a fundamental chemical reaction and is a step in many stoichiometric and catalytic processes. Some ions and molecules can undergo more than one protonation and are labeled polybasic, which is true of many biological macromolecules.

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