Peroxynitrite Reactions with Dimethylsulfide and Dimethylselenide: An Experimental Study

Abstract

The kinetics of the peroxynitrite (ONOO- and HOONO, PN for both) reaction with (Me)2X (X = S and Se, dimethyl sulfide (DMS) and dimethylselenide (DMSe)) was studied. The reaction is first order with respect to both PN and (Me)2X concentrations. (Me)2XO and NO2- were formed with 100% yield based on PN in all cases except in the DMS reaction with HOONO, where the yield was ∼80%. DMSe is much more reactive than DMS toward both ONOO- and HOONO, while HOONO reacts much faster than ONOO- with both (Me)2X. The activation entropies (in cal deg-1 mol-1) and enthalpies (given in parentheses, in kcal/mol) for the reactions of DMS and DMSe with HOONO were determined to be −23 ± 3 (5.9 ± 0.5) and −20.5 ± 3 (4.6 ± 0.5), respectively. The corresponding values for the reaction with ONOO- were −29 ± 3 (9.7 ± 0.6) and −28 ± 3 (7.2 ± 0.5). A partial replacement of water with an organic cosolvent resulted in a decrease in the rate of reaction of ONOO- with both DMS and DMSe, while it had no effect on the rates of reaction wi...