PhSO2Cl

PhSO2Cl, or benzenesulfonyl chloride (also called phenylsulfonyl chloride), is an aryl sulfonyl chloride derived from benzene. Its chemical formula is C6H5SO2Cl, and it has a molecular weight of about 176.6 g/mol. It is a reactive, moisture-sensitive reagent used widely in organic synthesis to introduce the sulfonyl group onto nucleophiles.

Physical and chemical properties: PhSO2Cl is typically a colorless to pale yellow liquid with a strong, pungent odor. It hydrolyzes readily in the presence of water, converting to benzenesulfonic acid and hydrogen chloride. It is soluble in a range of organic solvents such as dichloromethane, acetone, and ethers, and it reacts with many nucleophiles under appropriate conditions.

Reactions and applications: As an electrophilic sulfonylating agent, PhSO2Cl reacts with amines to form sulfonamides (R-SO2-NR2), with alcohols to give sulfonate esters (R-O-SO2-Ph), and with thiols to form sulfonothioates. These transformations are common tools in pharmaceutical synthesis and in the preparation of sulfonylated intermediates. PhSO2Cl is frequently used to activate substrates for nucleophilic substitution and to convert amine functionalities into sulfonamide protections in multistep synthetic sequences (though protecting-group choices such as tosyl or nosyl are also common in practice).

Handling and safety: PhSO2Cl is corrosive and an irritant; it poses risks to skin, eyes, and the respiratory system. It reacts with moisture to release HCl, so it must be stored and handled under strictly dry conditions, in a well-ventilated area, typically in a tightly closed container away from water and bases. Proper personal protective equipment and practices in a fume hood are recommended.

See also: other sulfonyl chlorides such as methanesulfonyl chloride and p-toluenesulfonyl chloride, which are used for related sulfonylation purposes.