title: Effect of Sterical Shielding on the Redox Properties of Imidazoline and Imidazolidine Nitroxides.
abstract: The oxidant properties of the series of 2,2,5,5-tetraalkyl imidazoline and imidazolidine nitroxides were investigated. An increase in the number of bulky alkyl substituents leads to a decrease in the rate of reduction with ascorbate, which makes the electrochemical reduction potential more negative and shifts the equilibrium in the mixture of nitroxide and reference hydroxylamine (3-carboxy-1-hydroxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl-1-(15)N) toward the starting compounds. The effect of structural factors on these reactions was analyzed by means of multiple regression using the Fujita steric constant Es and the inductive Hammett constant σI. Satisfactory statistical outputs were obtained in all of the biparameter correlations, denoting that the oxidant properties of the nitroxides are determined by steric and electronic effects of the substituents. The data imply that bulky substituents can stabilize nitroxide and/or destabilize hydroxylamine.
authors: N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS , Academician Lavrentjev Avenue 9, Novosibirsk, 630090, Russia.|Novosibirsk State University , Pirogova str. 2, Novosibirsk 630090, Russia.
authors: Igor A
authors: IA
authors: Kirilyuk
authors: Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, Department of Internal Medicine, The Ohio State University , Columbus, Ohio 43210, United States.
authors: Andrey A
authors: AA
authors: Bobko
authors: Novosibirsk State University , Pirogova str. 2, Novosibirsk 630090, Russia.
authors: Sergey V
authors: SV
authors: Semenov
authors: N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS , Academician Lavrentjev Avenue 9, Novosibirsk, 630090, Russia.|Novosibirsk State University , Pirogova str. 2, Novosibirsk 630090, Russia.
authors: Denis A
authors: DA
authors: Komarov
authors: N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS , Academician Lavrentjev Avenue 9, Novosibirsk, 630090, Russia.|Novosibirsk State University , Pirogova str. 2, Novosibirsk 630090, Russia.
authors: Irina G
authors: IG
authors: Irtegova
authors: N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS , Academician Lavrentjev Avenue 9, Novosibirsk, 630090, Russia.
authors: Igor A
authors: IA
authors: Grigor'ev
authors: N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS , Academician Lavrentjev Avenue 9, Novosibirsk, 630090, Russia.|Novosibirsk State University , Pirogova str. 2, Novosibirsk 630090, Russia.
authors: Elena
authors: E
authors: Bagryanskaya