pH-Sensitive C-ON Bond Homolysis of Alkoxyamines of Imidazoline Series: A Theoretical Study

pH-Sensitive C-ON Bond Homolysis of Alkoxyamines of Imidazoline Series: A Theoretical Study Full article

Journal

Journal of Physical Chemistry B
ISSN: 1520-6106

Output data

Year: 2014, Volume: 118, Number: 20, Pages: 5542-5550 Pages count : 9 DOI: 10.1021/jp5024372

Authors

Parkhomenko Dmitriy A. ^2,3,1 , Edeleva Mariya V. ³ , Kiselev Vitaly G. ^2,4 , Bagryanskaya Elena G. ^2,3,1

Affiliations

1	(Данные Web of science) NN Vorozhtsov Novosibirsk Inst Organ Chem SB RAS, Novosibirsk 630090, Russia
2	(Данные Web of science) Novosibirsk State Univ, Novosibirsk 630090, Russia
3	(Данные Web of science) Int Tomog Ctr SB RAS, Novosibirsk 630090, Russia
4	(Данные Web of science) Inst Chem Kinet & Combust SB RAS, Novosibirsk 630090, Russia

The pH-dependent kinetics of C-ON bond homolysis reactions of the four alkoxyamines (viz., the derivatives of 2-(4-(dimethylamino)-2-ethyl-5,5-dimethyl-2-(pyridin-4-yl)-2,5-dihydro-1H-imidazol-1-oxyl and 2-(2-carboxyethyl)-5,5-diethyl-2,4-dimethyl-2,5-dihydro-1H-imidazol-1-oxyl) in water solution have been scrutinized using DFT calculations (M06-2X/6-311++G(2df,p) level of theory with the PCM model). On the basis of computations, the experimental results obtained before (J. Org. Chem. 2011, 76, 5558) have been rationalized. The concentration dependence of all possible protonated forms of the four alkoxyamines was obtained from pH measurements. The contributions of particular protonated forms into the overall rate constants of thermolysis were estimated using the DFT calculated Gibbs free energies Delta(0)(r)G of C-ON bond homolysis reactions. The computations revealed that the observed rate constants of thermolysis of the two species at several pH values are dominated by decomposition reactions of two or even three protonated forms. The observed trends in reactivity of the alkoxyamines were mainly attributed to destabilization of the radical products of C-ON bond scission reactions. A linear correlation between the sum of radical stabilization energies (RSEs) of products of thermolysis and the calculated Gibbs free energies of reactions was found for various protonated forms of the species studied. Apart from this, the linear correlation exists between the relative RSE and nitrogen hyperfine constants a(N) of various protonated forms of the nitroxide radical products.

Parkhomenko D.A. , Edeleva M.V. , Kiselev V.G. , Bagryanskaya E.G.
pH-Sensitive C-ON Bond Homolysis of Alkoxyamines of Imidazoline Series: A Theoretical Study
Journal of Physical Chemistry B. 2014. V.118. N20. P.5542-5550. DOI: 10.1021/jp5024372 WOS Scopus РИНЦ

Published online:	May 7, 2014
Published print:	May 22, 2014

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