Fu Yan-Hua, Jia Taixuan, Shen Guang-Bin, Zhu Xiao-Qing
College of Chemistry and Environmental Engineering, Anyang Institute of Technology Anyang Henan 455000 China
School of Medical Engineering, Jining Medical University Jining Shandong 272000 P. R. China.
RSC Adv. 2023 May 30;13(23):16023-16033. doi: 10.1039/d3ra02211k. eCollection 2023 May 22.
Nitrogen-containing heterocycles are an important class of antioxidants, and their reactivity and selectivity in hydrogen atom reactions have attracted significant interest from chemists. In this work, the kinetics of hydrogen atom transfer reactions from C(sp)-H bonds of 28 nitrogen-containing heterocycles, oxygen-containing heterocycles, alicyclic amines and cycloalkanes, which were denoted as XH, to the CumO˙ radical, were investigated. The characteristic physical parameter of the substrate, , the thermo-kinetic parameter Δ(XH), was determined using the kinetic equation [Δ = Δ(XH) + Δ(Y)] to quantitatively evaluate the H-donating ability of XH. The effects of the substrate structure, substituent attached to the nitrogen atom, and ring size on the H-donating ability were discussed carefully. By comparing the H-donating abilities of cycloalkanes, alicyclic amines and nitrogen/oxygen-containing heterocycles, the influence of the introduction of N, O, or carbonyl groups in the carbon ring on the H-donating ability of C(sp)-H bond was determined. The electronic, steric and stereo-electronic effects of the groups were also discussed. Herein, we not only quantitatively determined the H-donating ability of the substrate, but also provided ideas for the synthesis of new antioxidants.
含氮杂环是一类重要的抗氧化剂，它们在氢原子反应中的反应活性和选择性引起了化学家们的极大兴趣。在这项工作中，研究了28种含氮杂环、含氧杂环、脂环胺和环烷烃（记为XH）的C(sp)-H键向CumO˙自由基的氢原子转移反应动力学。利用动力学方程[Δ = Δ(XH) + Δ(Y)]确定了底物的特征物理参数——热动力学参数Δ(XH)，以定量评估XH的供氢能力。仔细讨论了底物结构、氮原子上连接的取代基以及环大小对供氢能力的影响。通过比较环烷烃、脂环胺和含氮/氧杂环的供氢能力，确定了碳环中引入N、O或羰基对C(sp)-H键供氢能力的影响。还讨论了这些基团的电子效应、空间效应和立体电子效应。在此，我们不仅定量测定了底物的供氢能力，还为新型抗氧化剂的合成提供了思路。
