Gaudel-Siri Anouk, Siri Didier, Tordo Paul
UMR-CNRS 6517, Universités d'Aix-Marseille 1 et 3, Faculté des Sciences de St-Jérôme, Case 521, 13397 Marseille Cedex 20 (France).
Chemphyschem. 2006 Feb 13;7(2):430-8. doi: 10.1002/cphc.200500308.
During nitroxide-mediated polymerization (NMP) in the presence of a nitroxide R2(R1)NO*, the reversible formation of N-alkoxyamines [P-ON(R1)R2] reduces significantly the concentration of polymer radicals (P*) and their involvement in termination reactions. The control of the livingness and polydispersity of the resulting polymer depends strongly on the magnitude of the bond dissociation energy (BDE) of the C-ON(R1)R2 bond. In this study, theoretical BDEs of a large series of model N-alkoxyamines are calculated with the PM3 method. In order to provide a predictive tool, correlations between the calculated BDEs and the cleavage temperature (Tc), and the dissociation rate constant (k(d)), of the N-alkoxyamines are established. The homolytic cleavage of the N-OC bond is also investigated at the B3P86/6-311++G(d,p)//B3LYP/6-31G(d), level. Furthermore, a natural bond orbital analysis is carried out for some N-alkoxyamines with a O-C-ON(R1)R2 fragment, and the strengthening of their C-ON(R1)R2 bond is interpreted in terms of stabilizing anomeric interactions.
在氮氧化物介导的聚合反应（NMP）中，在氮氧化物R2(R1)NO存在下，N-烷氧基胺[P-ON(R1)R2]的可逆形成显著降低了聚合物自由基（P）的浓度及其参与终止反应的程度。所得聚合物的活性和多分散性的控制在很大程度上取决于C-ON(R1)R2键的键解离能（BDE）的大小。在本研究中，使用PM3方法计算了一系列模型N-烷氧基胺的理论BDE。为了提供一种预测工具，建立了计算得到的BDE与N-烷氧基胺的裂解温度（Tc）和解离速率常数（k(d)）之间的相关性。还在B3P86/6-311++G(d,p)//B3LYP/6-31G(d)水平上研究了N-OC键的均裂。此外，对一些具有O-C-ON(R1)R2片段的N-烷氧基胺进行了自然键轨道分析，并根据稳定的端基异构相互作用解释了它们C-ON(R1)R2键的强化。
