25087-44-9Relevant academic research and scientific papers
Generation and reactivity of aromatic thioether radical cations in aqueous solution as studied by pulse radiolysis
Ioele, Marcella,Steenken, Steen,Baciocchi, Enrico
, p. 2979 - 2987 (1997)
The radical cations of thioanisole (1), p-methylthioanisole (2), and the benzyl phenyl sulfides 3-5 have been produced by pulse radiolysis in aqueous solutions, using SO4?- or Tl2+ as oxidizing species. The radical cations 1?+-5?+ exhibit very similar UV spectra, with strong absorptions between 300-350 and 500-600 nm. In contrast to aliphatic thioether radical cations, 1?+-5?+ do not undergo dimerization (via formation of a three-electron bond with the parent thioethers). In the absence of bases, 1?+ is a long-lived species with a lifetime >30 ms, whereas 3?+, 4?+, and 5?+ decay rapidly by both C-S bond and C-H bond cleavage with kC-H = 1.3 × 103 s-1 and kC-S = 1.3 × 103 s-1 for 3?+ and kC-H = 0.95 × 103 s-1 and kC-S = 2.65 × 103 s-1 for 4?+. In the presence of OH- or HPO42-, also 1?+ undergoes a deprotonation process, with a rate larger than those of the benzyl phenyl sulfide radical cations. For example, the rate constant for the OH--induced deprotonation is 3.4 x 107 M-1 s-1 for 1?+ and 9.5 x 106 M-1 s-1 for 3?+. Thioanisole radical cation 1?+ was also produced by reduction of thioanisole sulfoxide. Under these conditions, it was possible to study the reaction of 1?+ with a number of nucleophiles or electron donors. It was found that 1?+ reacts with I-, N3-, PhS-, PhSH, Br-, and SCN- by an electron transfer mechanism, producing the oxidized form of the nucleophile. This reaction is diffusion controlled with the first four nucleophiles, which are more easily oxidized than 1 (Eo - (Eo = 1.62 V) and with Br- (Eo = 1.96 V). NO3- (Eo = 2.3V) is unreactive (k 6 M-1 s-1).
Photoinduced hydrogen- and electron-transfer processes between chloranil and aryl alkyl sulfides in organic solvents. Steady-state and time-resolved studies
Del Giacco, Tiziana,Elisei, Fausto,Lanzalunga, Osvaldo
, p. 1701 - 1708 (2007/10/03)
The photochemical behavior of three aryl alkyl sulfides, thioanisole (TA), benzyl phenyl sulfide (BPS) and 4-methoxybenzyl phenyl sulfide (MBPS), sensitized by triplet chloranil (CA), was investigated by nanosecond laser flash photolysis and steady-state irradiation in CH2Cl2 and MeCN. The nature of the transients detected upon 355-nm laser excitation was independent of the molecular structure of the aryl alkyl sulfides but strongly affected by the solvent polarity. In particular, in CH2Cl2 the quenching process of triplet CA by aryl alkyl sulfides was accompanied by H- transfer, with formation of the CAH· and TA(-H)·/BPS(-H)·/MBPS(-H)· radicals. In contrast, a charge transfer process between triplet CA and aryl alkyl sulfides, with formation of the radical anion CA·- and radical cations of aryl alkyl sulfides, occurred in MeCN. In this solvent, a transient detected at long delay time was tentatively assigned to the anion CAH- formed by H-transfer between radical ions. In all experiments, transient species were characterized in terms of second-order decay rate constants and quantum yields of formation. Steady-state irradiation of the CA/TA system led to the stable photoadduct C6H5SCH2OC6Cl4OH in both CH2Cl2 and MeCN with quantum yields of 0.033 and 0.27, respectively. In contrast, aldehydes, thioacetals, and disulfides were the main products obtained upon irradiation of the CA/BPS and CA/MBPS systems. The photoaddition products were not observed, probably owing to their low stability. The nature of the photoproducts formed by irradiation of CA/aryl alkyl sulfides was independent of solvent properties, even though the reactivity was higher in MeCN than in CH2Cl2.
