Factors Influencing C−ON Bond Homolysis in Alkoxyamines: Unexpected Behavior of SG1 (<i>N</i>-(2-methyl-2-propyl)- <i>N</i>-(1-diethylphosphono-2,2-dimethylpropyl)-<i>N</i>-oxyl)-Based Alkoxyamines
作者:Denis Bertin、Didier Gigmes、Christophe Le Mercier、Sylvain R. A. Marque、Paul Tordo
DOI:10.1021/jo0495586
日期:2004.7.1
Alkoxyamines and persistent nitroxides are important regulators of nitroxide-mediated radical polymerization (NMP). Since the polymerization time decreases with the increasing equilibrium constant K (kd/kc), i.e., the increasing rate constant kd of the homolysis of the C−ON bond between the polymer chain and the nitroxide moiety, the factors influencing the cleavage rate constants are of considerable
烷氧基胺和持久性氮氧化物是氮氧化物介导的自由基聚合(NMP)的重要调节剂。由于聚合时间随着平衡常数K(k d / k c)的增加而减少,即聚合物链和氮氧化物部分之间C-ON键均化的速率常数k d的增加,因此影响裂解的因素速率常数引起了极大的兴趣。事实证明,基于SG1的烷氧基胺是用于各种单体NMP的最有效的烷氧基胺家族。因此,确定使SG1衍生物比TEMPO(2,2,6,6-四甲基哌啶-N-氧基)衍生物。与我们对TEMPO衍生物观察到的相反,我们观察到E a与BDE(CH)的关系有两个关系,一个关系是非极性释放的烷基自由基(E a(kJ / mol)= -133.0 + 0.72BDE)和另一个用于极性释放的烷基(E a(kJ / mol)= -137.0 + 0.69BDE)。然而,对于两个家族(SG1和TEMPO衍生物),C-ON键均解的速率常数k d与裂解温度T c相关(log(k d(s