In organic chemistry, methenium (also called methylium, carbenium, methyl cation, or protonated methylene) is a cation with the formula CH+
3. It can be viewed as a methylene radical (:CH
2) with an added proton (H+
), or as a methyl radical (•CH
3) with one electron removed. It is a carbocation and an enium ion, making it the simplest of the carbenium ions.
Methyl cation; Methylium
3D model (JSmol)
|Molar mass||15.035 g·mol−1|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Preparation and reactionsEdit
For mass spectrometry studies at low pressure, methenium can be obtained by ultraviolet photoionization of methyl radical, or by collisions of monatomic cations such as C+
with neutral methane. In such conditions, it will react with acetonitrile CH
3CN to form the ion (CH
It is seldom encountered as an intermediate in the condensed phase. It is proposed as a reactive intermediate that forms upon protonation or hydride abstraction of methane with FSO3H-SbF5. The methenium ion is very reactive, even towards alkanes.
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3 and CH+
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