Laser flash photolysis and CIDNP studies of steric effects on coupling rate constants of imidazolidine nitroxide with carbon-centered radicals, methyl isobutyrate-2-yl and tert-butyl propionate-2-yl

Laser flash photolysis and CIDNP studies of steric effects on coupling rate constants of imidazolidine nitroxide with carbon-centered radicals, methyl isobutyrate-2-yl and tert-butyl propionate-2-yl Full article

Journal

Journal of Organic Chemistry
ISSN: 0022-3263

Output data

Year: 2006, Volume: 71, Number: 16, Pages: 6044-6052 Pages count : 9 DOI: 10.1021/jo060787x

Authors

Zubenko Dmitry ¹ , Tsentalovich Yuri ¹ , Lebedeva Nataly ¹ , Kirilyuk Igor ² , Roshchupkina Galina ² , Zhurko Irina ² , Reznikov Vladimir ² , Marque Sylvain R.A. ³ , Bagryanskaya Elena ¹

Affiliations

1	(Данные Web of science) SB RAS, Int Tomog Ctr, Novosibirsk, Russia
2	(Данные Web of science) SB RAS, Inst Organ Chem, Novosibirsk, Russia
3	(Данные Web of science) Univ Provence, F-13397 Marseille 20, France

Time-resolved chemically induced dynamic nuclear polarization (TR-CIDNP) and laser flash photolysis (LFP) techniques have been used to measure rate constants for coupling between acrylate-type radicals and a series of newly synthesized stable imidazolidine N-oxyl radicals. The carbon-centered radicals under investigation were generated by photolysis of their corresponding ketone precursors RC(O)R (R=C(CH3)(2)-C(O)OCH3 and CH(CH3)-C(O)-OtBu) in the presence of stable nitroxides. The coupling rate constants k(c) for modeling studies of nitroxide-mediated polymerization (NMP) experiments were determined, and the influence of steric and electronic factors on kc values was addressed by using a Hammett linear free energy relationship. The systematic changes in k(c) due to the varied steric (E-s,E-n) and electronic (sigma(L, n)) characters of the substituents are well-described by the biparameter equation log(k(c)/M-1 s(-1) ) = 3.52 sigma(L,n) + 0.47E(s,n) + 10.62. Hence, k(c) decreases with the increasing steric demand and increases with the increasing electron-withdrawing character of the substituents on the nitroxide.

Zubenko D. , Tsentalovich Y. , Lebedeva N. , Kirilyuk I. , Roshchupkina G. , Zhurko I. , Reznikov V. , Marque S.R.A. , Bagryanskaya E.
Laser flash photolysis and CIDNP studies of steric effects on coupling rate constants of imidazolidine nitroxide with carbon-centered radicals, methyl isobutyrate-2-yl and tert-butyl propionate-2-yl
Journal of Organic Chemistry. 2006. V.71. N16. P.6044-6052. DOI: 10.1021/jo060787x WOS Scopus РИНЦ

Published print:

Aug 1, 2006

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