2-Methylpentane is a branched-chain alkane

Alkane

Alkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...

 with the molecular formula C₆H₁₄. It is a structural isomer of hexane

Hexane

Hexane is a hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC nomenclature, however, hexane is the unbranched isomer ; the other four structures...

composed of a methyl group bonded to the second carbon atom in a pentane chain. It is of similar structure to one of its isomers, 3-methylpentane, which has the methyl group located on the third carbon of the pentane chain.