Hydrogen transfer in protic solvents

Hydrogen transfer in protic solvents describes the tendency for Hydrogen ions to migrate, often spontaneously, creating acids and bases from substances with neutral acidity.

Autoprotolysis

In chemistry, autoprotolysis is a molecular autoionization, a chemical reaction in which a proton is transferred between two identical molecules, one of which acts as a Brønsted acid, releasing a proton that is accepted by the other molecule, which acts as a Brønsted base. Any chemical that contains both acidic hydrogen and lone pairs of electrons to accept H⁺ can undergo autoprotolysis.

For example, water undergoes autoprotolysis in the self-ionization of water reaction.

2 H₂O ⇌ OH⁻ + H₃O⁺

For example, ammonia in its purest form may undergo autoprotolysis:

2 NH₃ ⇌ NH−2 + NH+4

Another example is acetic acid:

2 CH₃COOH ⇌ CH₃COO⁻ + CH₃COOH+2

Lyate and lyonium ions

A lyate ion is the anion derived by the deprotonation of a solvent molecule. For example, a hydroxide ion is formed by the deprotonation of water, and methoxide (CH₃O⁻) is the anion formed by the deprotonation of methanol. Its counterpart is a lyonium ion, the cation derived by the protonation of a solvent molecule. For example, a hydronium ion is formed by the protonation of water, and CH₃OH+2 is the cation formed by the protonation of methanol.

Lyonium and lyate ions, resulting from molecular autoionization, contribute to the molar conductivity of protolytic solvents.

See also

• Onium ion, a protonated molecule more generally
• Ion transport number
• Ionic atmosphere

References