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

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posted on 18.10.2013, 00:00 by Paul Brémond, Teddy Butscher, Valérie Roubaud, Didier Siri, Stéphane Viel
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.