Hydrogen-Bonding Effects for the C-ON Bond Homolysis and Reformation Reactions of Alkoxyamines

摘要

N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxyprop-2-yl) hydroxylamine (BlocBuilder MA) is, among the commercially available alkoxyamines, one of the most efficient for nitroxide-mediated polymerization (NMP). However, recent results have shown that it does not perform well for the NMP of isoprene. The occurrence of intramolecular hydrogen bonding (IHB) between the carboxylic function and the diethoxyphosphoryl group has been proposed as the reason for its low efficiency. In this article, the presence of this IHB is confirmed using IR, P-31 NMR, P-31-H-1 HOESY, and DFT calculation results. The solvent effect on this IHB and consequently on k(d) values is also investigated. However, combining kinetic analysis and rate measurements in various solvents, the influence of this IHB on the C-ON bond homolysis and reformation in alkoxyamine is shown to be very weak.