Homolysis of N-alkoxyamines: A Computational Study

✍ Scribed by Anouk Gaudel-Siri; Didier Siri; Paul Tordo

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 268 KB
• Volume: 7
• Category: Article
• ISSN: 1439-4235
• DOI: 10.1002/cphc.200500308

✦ Synopsis

Abstract

During nitroxide‐mediated polymerization (NMP) in the presence of a nitroxide R^2^(R^1^)NO^.^, the reversible formation of N__‐alkoxyamines [PON(R__^1^)R^2^] reduces significantly the concentration of polymer radicals (P^.^) and their involvement in termination reactions. The control of the livingness and polydispersity of the resulting polymer depends strongly on the magnitude of the bond dissociation energy (BDE) of the CON(R^1^)R^2^bond. In this study, theoretical BDEs of a large series of model N__‐alkoxyamines are calculated with the PM3 method. In order to provide a predictive tool, correlations between the calculated BDEs and the cleavage temperature (T~c~ ), and the dissociation rate constant (k~d~ ), of the N‐alkoxyamines are established. The homolytic cleavage of the NOC bond is also investigated at the B3P86/6‐311++G(d,p)//B3LYP/6‐31G(d), level. Furthermore, a natural bond orbital analysis is carried out for some N‐alkoxyamines with a OCON(R__^1^)R^2^fragment, and the strengthening of their CON(R^1^)R^2^bond is interpreted in terms of stabilizing anomeric interactions.