Methyloxonium
Chemical compound
From Wikipedia, the free encyclopedia
The methyloxonium ion is a protonated methanol molecule. It is a kind of oxonium ion and is the conjugate acid of methanol.
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3D model (JSmol) |
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| Properties | |
| CH5O+ | |
| Molar mass | 33.049 g·mol−1 |
| Related compounds | |
Related compounds |
Dimethyloxonium, Trimethyloxonium, Ethyloxonium, Methylammonium |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Formation
Methyloxonium is formed when methanol is treated with a superacid which add a proton.[1]
When methanol undergoes autoprotolysis, if forms methyloxonium along with an equal amount of methoxide.[2]
- 2 CH3OH → CH3OH+2 + CH3O−
Dissolving trifluoromethanesulfonic acid in methanol, produces methyloxonium triflate.[3]
Heat of formation ΔHf° at standard conditions is 574.9 kJ/mol.[4]
Reactions
Methyloxonium is unstable in the presence of water as it reacts:
- CH3OH+2 + H2O → H3O+ + CH3OH[5]
Methyloxonium methylates nucleophiles by displacing a hydrogen ion and releasing a water molecule:[1]
- CH3OH+2 + ArH → CH3Ar + H2O + H+
Between 100 and 300 °C, methanol in superacids forms methyloxonium ions which then methylate themselves and polymerise to yield alkanes, toluene and other aromatic hydrocarbons.[1]
Methyloxonium forms in the interstellar medium, where it can be broken by UV light to form singlet methylene, or it can react with ethylene to form propylene.[6]