methylgroep

A methylgroep, or methyl group, is a functional group with the formula −CH3. It consists of a single carbon atom bonded to three hydrogen atoms. As the simplest alkyl group, it is a common substituent in organic molecules and is denoted by the prefix methyl- in systematic names. In most contexts, the methyl group is nonpolar and hydrophobic.

Chemically, the methyl group is relatively inert by itself, but it can participate in transformations when attached to a larger carbon framework. Oxidation of a methyl substituent on an aromatic or aliphatic ring can convert it to a carboxyl group, for example turning a methylbenzene (toluene) into benzoic acid under suitable conditions. Radical halogenation or other substitutions can occur at the methyl carbon, especially in benzylic or allylic positions, leading to benzyl halides and related products. The methyl group also features in reactions that transfer a CH3 unit, such as methylation reagents used in organic synthesis.

In aromatic chemistry, a methyl substituent on a benzene ring is an activating, ortho/para-directing group. This increases reactivity toward electrophilic substitution and influences the distribution of reaction products compared with unsubstituted benzene.

Biology and biochemistry recognize methyl groups as essential modifiers. Methylation involves transferring a methyl group from donors like S-adenosyl methionine to substrates such as DNA, RNA, proteins, or small molecules. DNA methylation, particularly at cytosine bases, is a major epigenetic mechanism that regulates gene expression and development in many organisms.

Common examples include methanol (CH3OH) and methane (CH4), illustrating the methyl unit's presence across chemistry and biology. The term methyl group describes the CH3 moiety attached to various parents in countless compounds.