Intramolecular Hydrogen Bond in Alkoxyamines. Influence on the C–ON Bond Homolysis

The
C–ON bond homolysis in alkoxyamines can be influenced
by the presence of an intramolecular hydrogen bond (IHB) between the
alkyl and the nitroxyl fragments, which leads to an 8-fold decrease
in the homolysis rate constant kd. When
the IHB is disrupted by the solvent or by substitution of the hydrogen
involved in the IHB by a protecting group (OMe, OAc, OBz, OBn, or
OTBDMS), a higher homolysis rate constant kd is observed, as expected from the correlations developed by Marque
(Bertin, D.; Gigmes, D.; Marque, S.; Tordo, P. Macromolecules 2005, 38, 2638−2650). Results were confirmed by DFT calculations at the B3LYP/6-31G­(d,p)
level.