Aminolysis of 4-Nitrobenzenesulfenyl Chloride

SummaryThe reactions of 4-nitrobenzenesulfenyl chloride withsubstituted benzylamines proceed through three pathways,the uncatalyzed (k 2 ) and catalyzed (k 3 ) paths includingsolvolysis (k o ) by the solvent. The large value of primarynormal kinetic isotope effects imply that the proton transferoccurs concurrently from benzylamine to Cl atom of thesubstrate. The β x and ρ x values for the catalyzed path, k 3 , are greaterthan those for the uncatalyzed path, indicating that greaterdegree of bond formation in the catalyzed TS compared tothe uncatalyzed TS.ExperimentalMaterials. 4-Nitrobenzenesulfenyl chlorideA. used as asubstrate was purchased from Aldrich without further puri-fication. Benzylamines, Aldrich and DMSO, Merck were ofthe best grade commercially avaliable and were generallyrecrystallized or distilled before use.Kinetic Measurements. The rates for aminolysis weremeasured spectrophotometrically in DMSO at 25 ± 0.1 o Cby following the decrease in absorbance due to disappear-ance of the substrate at wavelengths in the range of 320-332nm. The rate measurements were carried out using a HewlettPackard 8452 Diode Array spectrophotometer equippedwith a Shimadzu TB-85-thermo bath to keep the temperatureof the reaction mixture at 25 ± 0.1