Fragmentation of radical anions of polyfluorinated benzoates

Fragmentation of radical anions of polyfluorinated benzoates Научная публикация

Журнал

Journal of Physical Chemistry A
ISSN: 1089-5639

Вых. Данные

Год: 2000, Том: 104, Номер: 2, Страницы: 352-361 Страниц : 10 DOI: 10.1021/jp993361d

Авторы

Konovalov V.V. ^1,2 , Laev S.S. ³ , Beregovaya I.V. ³ , Shchegoleva L.N. ³ , Shteingarts V.D. ³ , Tsvetkov Yu.D. ¹ , Bilkis I. ⁴

Организации

1	(Данные Web of science) Russian Acad Sci, Siberian Branch, Inst Chem Kinet & Combust, Novosibirsk 630090, Russia
2	Ctr. for Mat. for Info. Technology, University of Alabama, Bevill Building, P.O. Box 870209
3	(Данные Web of science) Russian Acad Sci, Siberian Branch, Inst Organ Chem, Novosibirsk 630090, Russia
4	(Данные Web of science) Hebrew Univ Jerusalem, Fac Agr, IL-76100 Rehovot, Israel

A comprehensive study of the symmetry forbidden fragmentation of short-lived radical anions (RAs) has been undertaken for the complete set of polyfluorinated benzoates (C6FnH5-nCO2-, n = 1-5) The decay rate constants (k(c)) of RAs have been determined in aqueous alkaline solution (pH 13.4) by electron photoinjection (EPI) from mercury electrodes and were found to increase dramatically from less than or equal to 3 x 10(3) s(-1) (3-F-C6H4CO2-) to (1.2 +/- 0.8) x 10(9) s(-1) (C6F5CO2-). The regioselectivity of C-F bond cleavage in the RA fragmentation has been revealed by structure assignment of reduction products of the polyfluorinated benzoic acids by Na, K, and Zn in liquid NH3, as well as by Zn in aqueous NH3 and aqueous alkaline solutions. The k(c) values depend on the position of the cleaved fluorine to the CO2- group generally in the order para > ortho > meta, and to sharply increase if adjacent fluorine atoms are present. The observed trends reveal that the kinetics of the RA fragmentation reaction is not controlled by the reaction thermodynamics. Semiempirical UHF/INDO calculations, the validity of which has been confirmed by ab initio ROHF/6-31+G calculations, were done to rationalize the observed trends. The reaction transition state (TS) was considered to arise from the RA's II and Sigma* states crossing avoided due to out-of-plane deviation of the cleaving C-F bond. The satisfactory Linear correlation (R = 0.96) between the model reaction energy barrier E-a and log k(c) has been achieved with modeling the local solvation of the CO2- group by its protonation.

Konovalov V.V. , Laev S.S. , Beregovaya I.V. , Shchegoleva L.N. , Shteingarts V.D. , Tsvetkov Y.D. , Bilkis I.
Fragmentation of radical anions of polyfluorinated benzoates
Journal of Physical Chemistry A. 2000. V.104. N2. P.352-361. DOI: 10.1021/jp993361d WOS Scopus РИНЦ

Опубликована в печати:

1 янв. 2000 г.

Web of science	WOS:000085006000023
Scopus	2-s2.0-0000376764
РИНЦ	13348357
OpenAlex	W1978635271