Methyl group

Methyl groups can be incorporated into organic compounds by an S_N2 reaction on iodomethane, or by the reaction of methyl lithium or MeMgCl with a carbon atom that is substituted with a leaving group.

Reactivity

The introduction of methyl groups as substituents into a compound usually increases its lipophilicity and reduces its solubility in water. It should ease its absorption into biological membranes and make its release into aqueous surroundings more difficult. Incorporating a methyl group into a molecule can have any of three effects, each increasing its reactivity (the rate of its metabolism):

1. by oxidizing the methyl group,
2. by demethylation (the transfer of the methyl group to another compound), or
3. by reduction, reducing the analogue.

The reactivity of a methyl group depends on what it is attached to. When occurring in an alkane, it is quite unreactive and resists all but the strongest of acids, bases, oxidizing agents, and reducing agents. But in toluene, C₆H₅CH₃, the methyl group is considerably more reactive, due to the electron donating propensity of the ring. Electrophilic reagents are then able to attack the methyl group. For example, oxidation with permanganate converts the methyl group to carboxyl (-COOH), to produce benzoic acid.

Methyl radical

The methyl radical is the substance CH₃ on its own, with an unpaired electron. Though it readily dimerizes to ethane, it is stable enough (unlike atomic hydrogen) to be observed as a dilute gas. It can be produced by thermal decomposition of certain compounds, especially those with a -N=N- linkage, which lose the extremely stable dinitrogen molecule on heating.

See also

• methanol history for the etymology of methyl

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