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The degradation of carbendazim (CBZ) through TiO2 photocatalysis, in the presence of halide ions and under near-UV light irradiation, was investigated. HPLC–MS technique was used to characterize the photoproducts. Spectrophotometric analysis showed that CBZ degraded slowly in TiO2 aqueous dispersions containing no salt (CBZ conversion of 6% after ca. 5 h of irradiation). The photodegradation efficiency increased particularly by addition of bromide salts. Indeed, CBZ reached complete degradation after ca. 30 min at the maximum concentration of NaBr used (0.05 M). Two significant aspects have emerged from the data analysis: the bromide role is to cause inhibition of the electron–hole recombination, a reaction known to be competitive with the reactive process; CBZ photodegradation is especially initiated by direct hole transfer pathway, whereas the OH• role is crucial in the catalyst regeneration process. Degradation attempts under sunlight appeared promising for a more sustainable photocatalytic process. [ABSTRACT FROM AUTHOR]

In this study, oxidative degradation of Orange G (OG) and Eosin Y (EY) dyes with TiO2 as the catalyst was explored in air-equilibrated aqueous dispersions under UV light irradiation. To determine the optimal operating conditions for degradation, various effects were investigated, such as the pH of the dye dispersion, the addition of cationic surfactants and the specific additive. The photodegradation efficiency of both dyes was significantly enhanced at alkaline pH, particularly in the presence of tetraalkylammonium bromide surfactants, as they promote a mutual interaction between the dye and TiO2 surface, otherwise prevented due to their negative charge under basic conditions. The surfactant concentration also played an important role, because it influences the state of surfactant aggregation on the semiconductor surface. The kinetic trend of the fragmentation process was strongly affected by different hydrophobic and electrostatic interactions that OG and EY and their derivative intermediates are able to establish with surfactant/TiO2 in various forms of aggregation, as well as by their redox properties. Density functional theory (DFT) calculations of charge distribution and Gibbs free energy changes of solvation, performed on optimized molecular geometry, were useful to support and rationalize the surfactant involvement in the degradation process. [ABSTRACT FROM AUTHOR]

A steady state and laser photolysis study of the oxidation reactions of benzyltrimethylsilane and (4-methoxybenzyl)trimethylsilane is described. Chloranil-sensitized oxidation of both compounds were carried out in various solvents, benzene, Ch2Cl2 and MeCN, which exhibited significantly different polarity and nucleophilic characteristics. The results showed the important role of solvent and substrate structure with respect to the quenching to triplet chloranil and to regiochemistry.

A kinetic and product study of the 3‐cyano‐N‐methyl‐quinolinium photoinduced monoelectronic oxidation of a series of β‐hydroxysulfoxides has been carried out to investigate the competition between Cα‐S and Cα‐Cβ bond cleavage within the corresponding cation radicals. Laser flash photolysis experiments unequivocally established the formation of sulfoxide cation radicals showing their absorption band (λmax ≈ 520 nm) and that of 3‐CN‐NMQ• (λmax ≈ 390 nm). Steady‐state photolysis experiments suggest that, in contrast to what previously observed for alkyl phenyl sulfoxide cation radicals that exclusively undergo Cα‐S bond cleavage, the presence of a β‐hydroxy group makes, in some cases, the Cα‐Cβ scission competitive. The factors governing this competition seem to depend on the relative stability of the fragments formed from the two bond scissions. Substitution of the β‐OH group with ‐OMe did not dramatically change the reactivity pattern of the cation radicals thus suggesting that the observed favorable effect of the hydroxy group on the Cα‐Cβ bond cleavage mainly resides on its capability to stabilize the carbocation formed upon this scission. [ABSTRACT FROM AUTHOR]

A combination of steady-state irradiation and nanosecond laser flash photolysis under nitrogen in MeCN is employed to study the 3-cyano-N-methylquinolinium perchlorate photosensitized oxidation of phenyl alkyl sulfoxides. The heterolytic C-S bond cleavage in the sulfoxide radical cations is shown to lead to the formation of several products, including alcohols and acetamides.

A study reports information on spectral properties and the structure of aryl methyl sulfoxide radical cations, using pulse radiolysis and laser flash photolysis techniques. In water, the radical cations of 4-X'C6H4SOMe generated by pulse radiolysis at pH 4, present an intense absorption in the ultraviolet region and a broad less intense band in the visible region whose position depends on the nature of the ring substituent.