Lund Torben, Christensen Peter, Wilbrandt Robert
Institute of Life Science and Chemistry, Roskilde University, DK-4000, Denmark.
Org Biomol Chem. 2003 Mar 21;1(6):1020-5. doi: 10.1039/b209594g.
Coupling rates between the radicals methyl, n-, sec-, tert-butyl and benzyl (R.) and the aromatic radical anions of 1,4-dicyanonaphthalene, 9,10-dicyanoanthracene and fluorenone (A-.) have been obtained using a new laser-flash photolysis method. The radicals R. and the radical anions A-. were generated by a photoinduced electron transfer reaction between the aromatic compound A and the alkyl or benzyl triphenylborate anion RB(Ph)3-. For the first time the rate constants of the coupling reaction between methyl and benzyl radicals with aromatic radical anions have been obtained. For all the measured coupling rate constants an average value of k1 = 1.9 x 10(9) M-1 s-1 was found with a relatively small variation in the coupling rates (0.8-2.9 x 10(9) M-1 s-1). The results demonstrate that the coupling rate k1 is insensitive to changes in the steric and electronic properties of the radicals and the structure and standard potentials of the aromatic radical anions.
采用一种新的激光闪光光解方法，已获得甲基、正丁基、仲丁基、叔丁基和苄基自由基（R·）与1,4 - 二氰基萘、9,10 - 二氰基蒽和芴酮的芳族自由基阴离子（A -·）之间的偶合速率。自由基R·和自由基阴离子A -·是通过芳族化合物A与烷基或苄基三苯基硼酸根阴离子RB(Ph)₃⁻之间的光诱导电子转移反应产生的。首次获得了甲基和苄基自由基与芳族自由基阴离子之间偶合反应的速率常数。对于所有测得的偶合速率常数，发现其平均值k₁ = 1.9×10⁹ M⁻¹ s⁻¹，偶合速率的变化相对较小（0.8 - 2.9×10⁹ M⁻¹ s⁻¹）。结果表明，偶合速率k₁对自由基的空间和电子性质以及芳族自由基阴离子的结构和标准电位的变化不敏感。
