propyl

Propyl is a three-carbon alkyl substituent derived from propane by removing one hydrogen atom. As a substituent, it can join a molecule via a single carbon–carbon bond. There are two structural isomers used in organic chemistry: propan-1-yl, commonly known as n-propyl, and propan-2-yl, commonly known as isopropyl. In IUPAC nomenclature, these are called propan-1-yl and propan-2-yl, while the common names n-propyl and isopropyl remain widely used.

In chemical synthesis, propyl groups are attached to parent molecules to modify properties such as lipophilicity, volatility, or steric profile. They are found in a broad range of compounds, including propanol isomers (propan-1-ol and propan-2-ol), propyl esters (for example, propyl acetate), and propyl ethers (such as di-n-propyl ether). Propyl groups also appear in alkyl halides (such as 1-chloropropane) and in various organometallic reagents used in alkylation reactions.

The two propyl isomers differ in shape and reactivity due to branching: n-propyl is a straight-chain fragment, while isopropyl is branched, which can influence steric effects in chemical reactions and the physical properties of the compounds to which they are attached. As a substituent, propyl serves as a common building block in organic synthesis and in the design of molecules with targeted properties.