84017-07-2Relevant academic research and scientific papers
A Kinetic Study on Oxidation of a Pair of Associating Thiols Having Substituted PhenylGroups with Oxygen
Endo, Tadashi,Hashimoto, Masao,Orii, Toyohiko,Ito, Masato, M.
, p. 1562 - 1566 (2007/10/02)
The rates of oxidation of 1:1 mixtures of associating thiols, each having the binding site (-CONHCONH-) and the recognition site , with O2 were measured in 80percent (v/v) acetonitrile-20percent water in the range of 20 to 50 deg C.Oxidation of the thiol having the p-(CH3)2NC6H4 group proceeds about 100 times faster than that of the thiols with R.It has been found that oxidation of 1:1 mixtures of the thiols is first-order with respect to thiols and 0.7 th-order with respect to triethylamine by means of the method of initial rates.The k1.7 values for R = C6H5, p-CH3C6H4, and p-C2H5C6H4 were similar to one another; this makes a sharp contrast with our previous work that the selectivity (the logarithmeric ratio of the yield of the unsymmetrical disulfide to twice that of the symmetrical disulfide) changes greatly with the structures of R and temperature.It is concluded that the product ratio does not depend upon the k1.7.The large negative activation entropies (-51 to -45 cal K-1 mol-1) suggest that the oxidation would proceed through a highly ordered transition state.
SPECIFIC RECOGNITION OF NONPOLAR GROUPS IN AQUEOUS MEDIA. LARGER SELECTIVITY DIFFERENCES IN OXIDATION OF ASSOCIATING THIOLS IN AQUEOUS MIXED SOLVENTS THAN IN NONAQUEOUS ONES
Endo, Tadashi,Takei, Hiromichi,Guro, Kazuo,Yamashita, Minoru,Yonenaga, Shu,et al.
, p. 1717 - 1720 (2007/10/02)
Environment dependence of the selectivity in oxidation of a pair of associating thiols was examined in binary solvent mixtures of an alcohol or acetonitrile with water and an organic cosolvent.The discrimination between the two nonpolar groups (n- and i-C5H11 groups, phenyl and p-tolyl groups, or n- and i-C4H9 groups) of one of the thiols was found to occur more specifically in aqueous media than in the corresponding nonaqueous media.
Methylation of a Benzene Ring as a Chemical Signal. Marked Changes in the Pattern of Temperature Dependence of the Selectivity in Oxidation of a Pair of Associating Thiols
Endo, Tadashi,Okubo, Akihiro,Kaneko, Yuji,Uehara, Masatoshi,Tasai, Hidetoshi,et al.
, p. 2224 - 2232 (2007/10/02)
Temperature dependence of the selectivity has been studied in oxidation of a pair of assotiating thiols, each with the recognition site 1>, with O2 in 80percent (v/v) acetonitrile-20percent water in the range of -10 to 70 deg C.The selectivity for R1=C6H4CH3 shows a minimum at 35 deg C, whereas for R1=C6H5 the selectivity exhibits a maximum at 35 deg C; for R1=C6H4C2H5 plots of the selectivity against temperature shows a sigmoid-like curve.The selectivity in oxidation of a pair of non-associating thiols, 2-(dimethylamino)ethanethiol and a para-substituted benzenethiol, remains practically unaltered with temperature in the same solvent.Though thiol-disulfide exchange reaction proceeds slowly below 35 deg C, the selectivity in the exchange differs entirely from that in the oxidation.It has been found that changes in hydrophobocity with R1 and temperature cannot explain dramatic alterations in the selectivity with R1 and temperature.
