Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma, Piazzale A. Moro 5, I-00185 Rome, Italy.
J Org Chem. 2010 Mar 5;75(5):1378-85. doi: 10.1021/jo100040y.
The reaction of the benzotriazole N-oxyl radical (BTNO) with a series of 4-X-N,N-dimethylanilines (X = CN, CF(3), CO(2)CH(2)CH(3), CH(3), OC(6)H(5), OCH(3)) has been investigated in CH(3)CN. Product analysis shows that the radical, 4-X-C(6)H(4)N(CH(3))CH(2)(), is first formed, which can lead to the N-demethylated product or the product of coupling with BTNO. Reaction rates were found to increase significantly by increasing the electron-donating power of the aryl substituents (rho(+) = -3.8). With electron-donating substituents (X = CH(3), OC(6)H(5), OCH(3)), no intermolecular deuterium kinetic isotope effect (DKIE) and a substantial intramolecular DKIE are observed. With electron-withdrawing substituents (X = CN, CF(3), CO(2)CH(2)CH(3)), substantial values of both intermolecular and intramolecular DKIEs are observed. These results can be interpreted on the basis of an electron-transfer mechanism from the N,N-dimethylanilines to the BTNO radical followed by deprotonation of the anilinium radical cation (ET-PT mechanism). By applying the Marcus equation to the kinetic data for X = CH(3), OC(6)H(5), OCH(3) (rate-determining ET), a reorganization energy for the ET reaction was determined (lambda(BTNO/DMA) = 32.1 kcal mol(-1)). From the self-exchange reorganization energy for the BTNO/BTNO(-) couple, a self-exchange reorganization energy value of 31.9 kcal mol(-1) was calculated for the DMA(+)/DMA couple.
苯并三唑氮氧自由基（BTNO）与一系列 4-X-N,N-二甲基苯胺（X = CN、CF₃、CO₂CH₂CH₃、CH₃、OC₆H₅、OCH₃）在 CH₃CN 中的反应已经被研究过。产物分析表明，自由基 4-X-C₆H₄N(CH₃)CH₂()首先形成，它可以导致 N-去甲基化产物或与 BTNO 偶联的产物。发现反应速率随着芳基取代基的给电子能力（rho(+) = -3.8）的增加而显著增加。对于给电子取代基（X = CH₃、OC₆H₅、OCH₃），没有观察到分子间氘动力学同位素效应（DKIE）和显著的分子内 DKIE。对于吸电子取代基（X = CN、CF₃、CO₂CH₂CH₃），观察到分子间和分子内 DKIE 都有很大的值。这些结果可以根据从 N,N-二甲基苯胺到 BTNO 自由基的电子转移机制（ET-PT 机制），然后是苯胺自由基阳离子的去质子化来解释。通过将马库斯方程应用于 X = CH₃、OC₆H₅、OCH₃（决定 ET 的速率）的动力学数据，确定了 ET 反应的重组能（lambda(BTNO/DMA) = 32.1 kcal mol(-1)）。从 BTNO/BTNO(-)对的自交换重组能计算出 DMA(+)/DMA 对的自交换重组能值为 31.9 kcal mol(-1)。
