PhCH2CH2CH3

Propylbenzene, often written as PhCH2CH2CH3, is an aromatic hydrocarbon in which a linear three-carbon alkyl chain is attached to a benzene ring. Its common name is propylbenzene or, when distinguishing from isomers, n-propylbenzene. The IUPAC name is propylbenzene. The molecule has formula C9H12 and consists of a phenyl ring with a propyl side chain.

Physical and chemical properties: Propylbenzene is a colorless to pale yellow liquid at room temperature. It is relatively nonpolar and has limited water solubility, but mixes with many organic solvents. Its boiling point is high for a hydrocarbon of this size, typically around 210–215 °C. It is flammable and should be handled with standard precautions for volatile organic liquids.

Production and applications: Propylbenzene is produced mainly by the alkylation of benzene with propylene over catalysts such as aluminum chloride or similar Lewis acids, yielding the linear n-propyl substituent on the ring. It can also be obtained as a byproduct in certain refinery streams. Industrially, it serves as a solvent for waxes, oils, and resins, and it acts as an intermediate in the synthesis of fragrances, dyes, plastics, and various chemical products.

Reactivity and transformations: Like other alkylbenzenes, propylbenzene can undergo oxidation at the benzylic position to benzoic acid derivatives under strong oxidizing conditions. It can participate in electrophilic aromatic substitutions on the benzene ring (for example, nitration, halogenation) with regioselectivity governed by the alkyl substituent. Side-chain reactions and rearrangements are generally minimized under controlled conditions.

Safety: Propylbenzene is a flammable liquid and vapor; exposure can cause irritation. It should be stored in a well-ventilated area away from ignition sources and handled with appropriate PPE.