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

Article abstract of DOI:10.1246/bcsj.55.2224

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.