JACs Image Challenge
Sep 2012
Gryn'ova G., Ingold K.U., Coote M.L.,
New Insights into the Mechanism of Amine/Nitroxide Cycling during the Hindered Amine Light Stabilizer Inhibited Oxidative Degradation of Polymers
J. Am. Chem. Soc., (2012), 134, 12979-12988.
http://dx.doi.org/10.1021/ja3006379
Hindered amine light stabilizers (HALSs) are generally N-substituted tetramethylpiperidine-based radical-trapping antioxidants that are widely used to protect polymers from oxidative damage. The figure shows model alkoxyamines, formed from commercially available HALSs during the degradation of various substrates (R1-R3), and the corresponding free energies of N-O and O-bond homolyses. In which system(s) should formation of the secondary piperidines be expected?
(A) R1 and R2
(B) R2 only
(C) R1 and R3
(D) R3 only