C6H5CH2CH2

C6H5CH2CH2 is the condensed representation of the phenethyl group, also called the 2-phenylethyl substituent. It consists of a phenyl ring (C6H5) attached to a two-carbon chain (CH2–CH2–), with the attachment point at the terminal carbon. In shorthand, it is often written as Ph-CH2-CH2- and appears as a substituent in many organic compounds.

Nomenclature and relationships: The systematic name for this substituent is 2-phenylethyl. It is distinct from the benzyl group (Ph-CH2–), which contains only one CH2 linking the ring to the rest of the molecule. The phenethyl group is a common building block in pharmaceuticals, fragrances, and organic synthesis, and it is found in derivatives such as phenethyl alcohol (Ph-CH2-CH2–OH) and phenethylamine (Ph-CH2-CH2–NH2).

Reactivity and applications: The benzylic carbon (the CH2 directly attached to the aromatic ring) possesses relatively reactive C–H bonds, making functionalization at that position a common strategy in synthesis. Reactions may include benzylic oxidation, formation of phenylacetic derivatives, or other transformations that extend or modify the carbon chain attached to the ring. The phenethyl motif serves as a versatile aryl–alkyl linker in a wide range of compounds, contributing to the lipophilic character and structural diversity of the molecules.

Properties and context: As a structural fragment, the phenethyl group influences the physical properties of a molecule, typically increasing hydrophobicity. The neutral C8H9 fragment has a approximate molar mass of 105.16 g/mol. The significance of this group lies in its widespread use as a synthetic handle for building more complex structures in organic chemistry.