Four-centered concerted ethane elimination in the IR and UV laser photolysis of dimethyldisulfide. Real-time observation of S₂ and CH₃S radicals

Abstract

CO₂ and KrF laser-induced dissociation of dimethyl disulfide opens two major primary dissociation channels. The moleculer elimination channel produces S₂ and C₂H₆ via a four-centered transition state whereas the radical channel generates two CH₃S radicals. The time-resolved UV absorption spectra of the transients CH₃S and S₂ are reported. From the real time formation of CH₃S radical, a unimolecular dissociation rate constant for dimethyl disulfide has been found to be 6.8 × 10⁵ s^-1 and ≥ 1 × 10⁷ s^-1 in the IR and UV laser photolysis, respectively. In SF₆-sensitised dissociation of dimethyl disulfide, a time lag between the laser pulse and the onset of dissociation is observed, which is ascribed to intermolecular energy transfer from vibrationally excited SF₆ to the substrate.