In chemistry, a methyl group is a type of alkyl group with the formula CH3. It is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in 3 forms: anion, cation and radical. The anion has 8 valence electrons, the radical 7 and the cation 6. All three are highly reactive and rarely observed.
Methyl cation, anion, and radical
The methylium cation (CH3+) exists in the gas phase, but is otherwise not encountered. Some compounds are considered to be sources of "CH3+," and this simplification is used pervasively in organic chemistry. For example, protonation of methanol gives a strongly electrophilic methylating reagent:
Similarly, methyl iodide and methyl triflate are viewed as the equivalent of the methyl cation because they readily undergo a SN2 reactions by weak nucleophiles.
The methanide anion (CH3-) similarly exists only under exotic conditions. In discussing mechanisms of organic reactions, it is often a useful simplification to consider methyl lithium and related Grignard reagents as sal sources of "CH3-," although this view is fiction. Such reagents are generally prepared from the methyl halides:
where M is alkali metal.
The methyl radical has the formula CH3. It exists in dilute gases, but in more concentrated form it readily dimerizes to ethane. It can be produced by thermal decomposition of only certain compounds, especially those with an -N=N- linkage.
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