phenylCH2CH2

PhenylCH2CH2, commonly known as the phenethyl group or 2-phenylethyl substituent, is a two-carbon alkyl-phenyl linker used in organic molecules. The group consists of a phenyl ring (phenylic) attached to a two-carbon chain, Ph-CH2-CH2-, that connects to the rest of the molecule at the terminal carbon.

Structure and connectivity: In the phenethyl substituent, the phenyl ring is bonded to a methylene (benzylic) carbon, which in turn is bonded to another methylene carbon that forms the connection to the parent molecule (Ph-CH2-CH2–X). This two-carbon linker provides conformational flexibility and a moderate degree of lipophilicity. The unsubstituted phenethyl fragment has the chemical formula C8H9 and can be further modified by substituents on the phenyl ring or on the ethyl chain.

Nomenclature and synonyms: The substituent is frequently called the phenethyl group or 2-phenylethyl group. In systematic naming, it is described as a 2-phenylethyl substituent when accounting for the point of attachment to the rest of the molecule. It is related to the benzyl group (Ph-CH2-) by the presence of an additional CH2 unit.

Occurrences and uses: The phenethyl linker is a common building block in organic synthesis and medicinal chemistry. It serves as a spacer that can influence molecular lipophilicity, conformational dynamics, and interactions with biological targets. Phenethyl motifs appear in various pharmaceuticals, natural products, and research reagents, including phenethylamine derivatives and related frameworks.

See also: benzyl group, phenyl group, ethyl group, phenethylamine.