Photolytic Generation and the Subsequent Dimerization of 4-Alkyl-1-methylpyridinyl Radicals in Solution as Studied by Steady-state and Kinetic ESR Spectroscopy
4-alkyl-1-methylpyridinyl (alkyl=methyl, ethyl, isopropyl, and t-butyl) radicals were generated photolytically from their dimers in solution. Hyperfine splitting constants for these radicals were assigned and the temperature dependence was discussed. Absolute dimerization rates of these radicals in the range of −50–−100 °C were determined by analyzing the ESR signal decay during the dark period. A nearly constant activation
1-甲基吡啶基和 4-烷基-1-甲基吡啶基(烷基 = 甲基、乙基、异丙基和叔丁基)自由基是由它们的二聚体在溶液中光解产生的。指定了这些自由基的超精细分裂常数,并讨论了温度依赖性。这些自由基在 -50–-100 °C 范围内的绝对二聚率是通过分析黑暗时期的 ESR 信号衰减来确定的。观察到五个自由基的二聚活化能几乎恒定,而频率因子随着 4-取代基的体积增大而降低,这在二聚的空间位阻方面进行了讨论。