A competitive kinetics study of the reaction of Cl with CS2 in air at 298 K

Theoretical interpretation of the UV-vis spectrum of the CS2/Cl complex in the spectral region 320-550 nm

Accurate multireference configuration interaction and time-dependent density functional calculations have been performed to interpret the experimental UV-vis spectrum of the CS(2)/Cl complex in the spectral region 320-550 nm. The molecular structure of the complex responsible for the previously observed UV-vis spectrum is recognized as ClSCS, not ClCS(2). Two low-lying excited states of ClSCS, responsible for its optical absorption, have been identified and analyzed. Optical excitation of ClSCS leads to the excitation-specific bond elongation that may lead to photofragmentation of the molecule. In addition, experimental conditions for verifying the presence of ClCS(2) are identified and detailed characterization of its optically active excited states with possible photofragmentation pathways is given.

Photoinduced oxidation of Hg0(aq) in the waters from the St. Lawrence estuary

The oxidation of volatile aqueous Hg0 in aquatic systems may be important in decreasing the fluxes of Hg out of the water column. Using incubations of natural samples from the St. Lawrence River, we examined some of the parameters that control this oxidation. Hg0 was found to be chiefly mediated by UV radiation since (i) "dark" oxidation was not found to be statistically significant; (ii) visible light induced a significant but slow photooxidation (k = 0.09 h(-1)); and (iii) visible + UV radiation led to a faster photooxidation (k = 0.6-0.7 h(-1)), mainly because of UV-A induced reactions. Doubling UV irradiation did not increase the reaction rate of Hg0 photooxidation in natural water samples, indicating that some factor other than photon flux was rate limiting and suggesting that the reaction involves intermediate photoproduced oxidant(s). The addition of methanol, a *OH scavenger, decreased Hg photooxidation rates by 25% in brackish waters and by 19% in artificial saline water containing semiquinones, indicating that *OH may be partly responsible for Hg0 oxidation. Photooxidation rates were not affected by oxygen concentrations and did not decrease when samples were heat-sterilized, treated with chloroform, or filtered prior to exposure to light.

Transient resonance Raman and density functional theory investigation of the chlorine atom/carbon disulfide molecular complex involved in selective alkane photochlorination reactions

The structure and bonding of the chlorine atom/carbon disulfide (CS(2)/Cl) complex involved in selective photochlorination reactions with alkanes was directly probed using transient resonance Raman spectroscopy. The experimental Raman vibrational frequencies were compared to those computed from density functional theory calculations for probable structures of the CS(2)/Cl complex. Our results indicate that the S [double bond] C [double bond] S...Cl complex species is responsible for the approximately 370 nm transient absorption band observed after ultraviolet photolysis of CCl(4) in the presence of CS(2). We discuss the structure and properties of the S [double bond] C [double bond] S...Cl complex and compare them with those for the related benzene/Cl and pyridine/Cl complexes.