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Reactivity of the Thermally Stable Intermediates of the Reduction of SO2 on Carbons and Mechanisms of Insertion of Organic Moieties in the Carbon Matrix
文摘
The reduction of SO B>2 on carbons proceeds through reactive intermediates bound to the carbon matrix, whichwere postulated to be 1,2-oxathiene 2-oxide (or sultine), and 1,3,2-dioxathiolane that decomposes to producean episulfide and CO2. The reactivity of these intermediates was studied in this work through several reactions,using XPS and NMR spectra to postulate their mechanisms. When modified activated carbon obtained afterreaction with SO2 at 630  s/entities/deg.gif">C was heated at 900 s/entities/deg.gif">C, it was observed that the changes of the XPS spectrumresulted from the forward reaction of decomposition of the oxidized intermediate with S-transfer to producethe episulfide and CO2 and the reverse reaction with expulsion of SO2. Strong bases hydrolyzed thedioxathiolane intermediate and the episulfide. The thiolysis, aminolysis, and reaction of alkyl halides withmodified activated carbon occurred with the insertion of the organic moiety in the carbon matrix. Laserphotolysis at 266 nm in t-butanol showed insertion of t-butoxide on the matrix. Consistent mechanisms forthese reactions were postulated. These results provide additional evidence on the mechanism of reduction ofSO2 on carbons and the chemical nature of the intermediates, offering a new method to modify the physicaland chemical properties of a carbon matrix by functionalization with an organic moiety. | |
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