1methylpropyl

1-methylpropyl is a four-carbon alkyl substituent, commonly called sec-butyl. It corresponds to the butan-2-yl group and has the formula C4H9. The attachment to the rest of a molecule occurs at the secondary carbon of the butane skeleton, making this a secondary alkyl substituent. Structurally, the radical can be represented as -CH(CH3)-CH2-CH3, where the bond to the parent molecule is at the secondary carbon.

In systematic IUPAC nomenclature, the preferred name is butan-2-yl. The form 1-methylpropyl is an alternative name that reflects a methyl substituent on carbon 1 of a propyl chain. This substituent is one of the four C4H9 alkyl groups. The other three are n-butyl (butan-1-yl), isobutyl (2-methylpropyl), and tert-butyl (2-methylpropan-2-yl).

The 1-methylpropyl (sec-butyl) group appears in various organic compounds as a building block or substituent. Its steric and electronic properties differ from those of the other C4H9 isomers, which can influence reactivity and selectivity in chemical transformations. It is commonly encountered in synthetic chemistry, where it can be introduced or modified through standard alkylation and substitution reactions.