Ionization of Various Monofunctional Derivatives of Naphtalene by Bimolecular Free Electron Transfer

Aliaksandr Baidak 

Interdisciplinary Group Time-Resolved Spectroscopy, University of Leipzig, Permoserstrasse 15, Leipzig 04303, Germany

Abstract

Radiolysis of non-polar media leads to the formation of radical cations. Parent radical cations derived from non-polar solvents such as n-alkanes, cycloalkenes and alkyl chlorides are extremely efficient electron acceptors. Easily they ionize practically all solutes with a diffusion-controlled reaction which is called as free electron transfer (FET) [1]. This reaction type is well studied by pulse radiolysis. FET exhibits some peculiarities which are determined by the properties of non-polar system. In the case of FET the ions are weakly solvated and possess the high excess energy of the reaction, and, accordingly, only limited stabilization of the products is possible. It must be stressed that the electron jump takes place in the first encounter of the reactants in extremely short time (≤10-15 s), without the formation of encounter complex.

For pulse radiolytically initiated electron transfer from α- and β-naphtols as well as naphtylamines and thionaphtols, two reaction pathways have been observed, resulting in simultaneous formation of (1) metastable radical cations of solutes with lifetimes in μs time range, and (2) unstable radical cations, which deprotonate immediatly after formation, producing heteroatom-centred radicals (-O˙, -NH˙, -S˙).

These experimental facts can be explained if one takes into account that electron transfer takes place in a singe rapid step which is faster than molecule deformation motions.

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So the distribution of rotation-conditioned conformers of the solute is reflected by the geometry of the radical cations produced. In this manner product radical cations of different stability are produced, which are distinguishable by their properties.

[1] O. Brede, Res. Chem. Intermed. 2001, Vol. 27, No. 7, 8, pp. 709-715.

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Presentation: oral at 18th Conference on Physical Organic Chemistry, Symposium 1, by Aliaksandr Baidak
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-05-31 16:31
Revised:   2009-06-07 00:44
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