Metüül

Metüül, or the methyl group, is the simplest alkyl substituent in organic chemistry. It consists of a single carbon atom bonded to three hydrogen atoms, giving the formula CH3–. When attached to a larger carbon skeleton, it acts as a substituent and is common in alkanes, alcohols, aromatics and many biomolecules. In shorthand, chemists write Me– to denote the methyl group.

The term metüül is Estonian for the methyl substituent; in IUPAC nomenclature the substituent is methyl, and its derivatives include methyl esters, methyl ethers, and methylated aromatics.

Methyl groups participate in many reactions. Benzylic and allylic C–H bonds adjacent to aromatic or vinyl groups are relatively reactive in radical halogenation, enabling formation of benzyl halides from toluene derivatives. Oxidation of a methyl substituent on an alkyl or aryl group can yield formyl or carboxyl groups (for example, Ar–CH3 → Ar–CHO → Ar–COOH) under appropriate conditions. Methylation reagents such as methyl iodide CH3I transfer the CH3 group to nucleophiles, creating methyl ethers, amines, and other methylated products. The presence of a methyl group also influences physical properties, often increasing hydrophobicity and affecting sterics.

Methyl groups are widespread in organic molecules, including methanol, methane-derived compounds, amino acids, nucleotides, and lipids. In biology, DNA and histone methylation modulates gene expression and protein function, making metüül groups central to metabolism and regulation.

Methyl-containing compounds range from relatively benign solvents to toxic reagents; many methylating agents are hazardous and handling requires proper safety measures.