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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