Methenium

In organic chemistry, methenium (also called methylium, the methyl cation, or protonated methylene) is a positive ion 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.

The methenium ion is planar or nearly planar, with threefold symmetry.

For mass spectrometry studies at low pressure, methenium can be obtained by ultraviolet photoionization of methyl radical, or by collisions of monatomic cations like C+
and Kr+
with neutral methane. In such conditions, it will react with acetonitrile CH
3CN to form the ion (CH
3)
2CN+
.

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