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Reduction of SO2 on Carbons. Reactivity of the Intermediates and Mechanisms of Insertion of Organic Moities on the Carbon Matrix

Eduardo Humeres 1Karen M. De Castro 1Regina F. Moreira 1Wido H. Schreiner 2Moisés Canle L 3Isabel Fernández 3Arturo Santaballa 3Abil E. Aliev 4Maria de Gloria B. Peruch 1

1. Universidade Federal de Santa Catarina (UFSC), Campus Universitario, Florianopolis 88040-900, Brazil
2. Universidade Federal de Parana (UFPR), Campus Universitario, Curitiba 00000-000, Brazil
3. Universidade da Coruña (UDC), Alejandro de la Sota, Coruña 15008, Spain
4. University College London (UCL), 20 Gordon Street, London WC1H, United Kingdom

Abstract

The reduction of SO2 on different carbons, proceeded through the same stoichiometric reaction [1], with increase of the S content and correspond to the reactive intermediates [2]. The sulfur was bound to carbon as 1,3,2-dioxathiolane and/or 1,2-oxathiene 2-oxide, that decompose producing an episulfide and/or disulfide, and CO2. Theoretical calculations supported the formation of the intermediates [3]. Consecutive reactions of insertion of S form a trisulfide that extrudes S2 regenerating 1 and stablish a transport mechanism [4].

In this work we have studied the reactivity of the intermediates. The reaction of graphite + SO2 at 630 oC showed the formation of the same intermediates as on activated carbon. When modified activated carbon obtained at 630 oC was heated at 900 oC, it was observed that the oxidized sulfur dissapeared with formation of free sulfur. The thiolysis, aminolysis and reaction of alkyl halide with modified activated carbon ocurred with insertion of the organic moiety and extrusion of SO2 as shown by the XPS and NMR spectra. Laser photolysis at 266 nm in t-butanol, showed the insertion of t-butoxide in the matrix, with extrusion of a sulfur-centered radical. These results provide additional evidences on the mechanism of reduction of SO2 on carbons, the chemical nature of the intermediates and offer a new method to modify the physical and chemical properties of the carbon matrix by insertion of an organic moiety.

[1] E. Humeres, R. F. P. M. Moreira, M. G. B. Peruch, Carbon 2002, 40, 751-760.

[2] E. Humeres, M. G. B. Peruch, R. F. P. M. Moreira, W. Schreiner, J. Phys. Org. Chem. 2003, 16, 824-830.

[3] J. R. Pliego, S. M. Resende, E. Humeres, Chem. Phys. 2005, 314, 127-133.

[4] E. Humeres, M. G. B. Peruch, R. F. P. M. Moreira, W. Schreiner, Int. J. Mol. Sci. 2005, 6, 130-142.

 

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Related papers

Presentation: oral at 18th Conference on Physical Organic Chemistry, Symposium 2, by Eduardo Humeres
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-05-05 15:18
Revised:   2009-06-07 00:44