Bagryanskaya Elena, Brémond Paul, Edeleva Mariya, Marque Sylvain R A, Parkhomenko Dmitriy, Roubaud Valérie, Siri Didier
International Tomography Center, Institutskaya 3A, 630090 Novosibirsk, Russia.
Aix-Marseille Université, case 521, Avenue Escadrille Normandie-Niemen, 13397 Marseille cedex 20, France.
Macromol Rapid Commun. 2012 Jan;33(2):152-7. doi: 10.1002/marc.201100590. Epub 2011 Nov 21.
In recent work, a 15-fold increase in the C-ON bond homolysis rate constant kd of 4-pyridylethyl-SG1-based alkoxyamine was observed upon protonation of the pyridyl moiety in organic solvent. In this report, the pH dependence of kd (pKa = 4.7) is investigated in D2O/CD3OD (v/v 1:1). A 64-fold increase in kd is observed at acidic pH. Calculations show that the increase in kd upon protonation is due to both an increase in the stabilization of the protonated 4-pyridylethyl radical and an increase of the destabilization of the starting materials through an increase in the polarity of the alkyl fragment. This new alkoxyamine is applied to NMP of styrene and sodium styrene sulfonate.
在最近的工作中，在有机溶剂中吡啶基部分质子化后，观察到基于4-吡啶基乙基-SG1的烷氧基胺的C-ON键均裂速率常数kd增加了15倍。在本报告中，在D2O/CD3OD（体积比1:1）中研究了kd的pH依赖性（pKa = 4.7）。在酸性pH下观察到kd增加了64倍。计算表明，质子化时kd的增加是由于质子化的4-吡啶基乙基自由基稳定性增加以及通过烷基片段极性增加导致起始原料去稳定化增加所致。这种新的烷氧基胺应用于苯乙烯和苯乙烯磺酸钠的氮氧介导聚合。
