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Inchemistry,autoprotolysis is amolecular autoionization, achemical reaction in which aproton is transferred between two identicalmolecules, one of which acts as aBrønsted acid, releasing a proton that is accepted by the other molecule, which acts as aBrønsted base.[1] Any chemical that contains both acidic hydrogen and lone pairs of electrons to acceptH+ can undergo autoprotolysis.
For example,water undergoes autoprotolysis in theself-ionization of water reaction.
For example,ammonia in its purest form may undergo autoprotolysis:
Another example isacetic acid:
A lyate ion is theanion derived by thedeprotonation of asolvent molecule.[2] For example, ahydroxide ion is formed by the deprotonation ofwater, andmethoxide (CH3O−) is the anion formed by the deprotonation ofmethanol. Its counterpart is a lyonium ion, thecation derived by theprotonation of asolvent molecule.[3] For example, ahydronium ion is formed by the protonation ofwater, andCH3OH+2 is the cation formed by the protonation ofmethanol.
Lyonium and lyate ions, resulting frommolecular autoionization, contribute to themolar conductivity of protolytic solvents.
| Lyate ion | Originalsolvent | Lyonium ion | |||
|---|---|---|---|---|---|
| name | formula | name | formula | name | formula |
| Fluoride | F− | Hydrogen fluoride | HF | Fluoronium | H2F+ |
| Hydroxide | OH− | Water | H2O | Hydronium | H3O+ |
| Azanide | NH−2 | Ammonia | NH3 | Ammonium | NH+4 |
| Methanide | CH−3 | Methane | CH4 | Methanium | CH+5 |
| Methoxide | CH3O− | Methanol | CH3OH | Methyloxonium | CH3OH+2 |