PhLi

PhLi, or phenyl lithium, is an organolithium reagent with the formula C6H5Li. It is a powerful base and nucleophile widely used in organic synthesis to form aryl metal intermediates and to construct carbon–carbon bonds. In practice, PhLi is typically encountered as a solution in hydrocarbon solvents such as hexane or cyclohexane, or in ethers, with common concentrations around 0.5–2 M.

Preparation of PhLi is usually achieved by halogen–lithium exchange from aryl halides, for example bromobenzene or chlorobenzene, with n-butyllithium or lithium metal in diethyl ether or THF. The resulting solution is highly reactive toward air, moisture, and heat and must be handled under an inert atmosphere and at low temperature to avoid runaway reactions.

Reactions and applications: PhLi serves as a strong nucleophile and base in many transformations. It can quench with carbon dioxide to yield benzoic acid after acidic workup; react with aldehydes and ketones to form secondary and tertiary alcohols; and participate in C–C bond-forming processes with electrophiles such as alkyl or acyl halides, or through transmetallation to other metals for subsequent coupling.

Stability and handling: Due to their high reactivity, PhLi reagents are extremely sensitive to air and moisture and are typically stored as solutions under inert gas in dry solvents at low temperatures. Contact with water or oxygen can ignite or cause violent reactions. Workups and transfers are performed under strictly dry, inert conditions with appropriate protective equipment and fire-suppression measures.

See also: organolithium reagents and halogen–lithium exchange.