Flash photolysis study for reactions of NO3· with sulfur compounds in acetonitrile solution

The rate constants for the reaction of NO₃· with sulfur compounds in acetonitrile have been determined by the flash photolysis method. The rate constant for dimethyl sulfone (2.7 × 10⁴ M^?1s^?1 at ?10°C) is larger than that of the deuterium derivative, indicating that NO₃· abstracts the hydrogen atom from dimethyl sulfone. In the case of dimethyl sulfide, the rate constant was evaluated to be 1.5 × 10⁹ M^?1 s^?1 at ?10°C; the transient absorption band attributable to the cation radical was observed after the decay of NO₃·, suggesting the electron transfer reaction from the sulfide to NO₃·. For diphenyl sulfide and dimethyl disulfide, the electron transfer reactions were also confirmed. For dimethyl sulfoxide, the reaction rate constant of 1.2 × 10⁹ M^?1 s^?1 (at ?10°C) was not practically affected by the deuterium substitution, suggesting that NO₃· adds to sulfur atom forming (CH₃)₂?(O)-ONO₂. On the other hand, for diphenyl sulfoxide, the electron transfer reaction occurs. By the comparison of these rate constants in acetonitrile solution with the reported rate constants in the gas phase, the change of the reaction paths was revealed.