title: Kinetic and computational evidence for an intermediate in the hydrolysis of sulfonate esters.
abstract: The hydrolytic reactions of sulfonate esters have previously been considered to occur by concerted mechanisms. We now report the observation of a break in a Brønsted correlation for the alkaline hydrolysis of aryl benzenesulfonates. On either side of a break-point, β(leaving group) values of -0.27 (pK(a) < 8.5) and -0.97 (pK(a) > 8.5) are measured. These data are consistent with a two-step mechanism involving a pentavalent intermediate that is also supported by QM/MM calculations. The emerging scenario can be explained by the combined effect of a strong nucleophile with a poor leaving group that compel a usually concerted reaction to favour a stepwise process.
authors: Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK.
authors: Ann C
authors: AC
authors: Babtie
authors: Marcelo F
authors: MF
authors: Lima
authors: Anthony J
authors: AJ
authors: Kirby
authors: Florian
authors: F
authors: Hollfelder
mesh_terms: D001557:Benzenesulfonates / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D006868:Hydrolysis; D006878:Hydroxides / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D017680:Potassium Compounds / Q000737:chemistry; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D001557:Benzenesulfonates; D004952:Esters; D006878:Hydroxides; D017680:Potassium Compounds; C032365:benzenesulfonic acid; C029943:potassium hydroxide