Radical/Ion Pair Formation in the Electrochemical Reduction of Arene Sulfenyl Chlorides

Important aspects of the electrochemical reduction of a series of substituted arene sulfenyl chlorides are investigated. A striking change is observed in the reductive cleavage mechanism as a function of the substituent on the aryl ring of the arene sulfenyl chloride. With p-substituted phenyl chlor...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2006-12, Vol.128 (48), p.15423-15431
Main Authors: Ji, Chang, Ahmida, Mohamed, Chahma, M'hamed, Houmam, Abdelaziz
Format: Article
Language:English
Subjects:
Chemistry
Exact sciences and technology
General and physical chemistry
Kinetics and mechanisms
Organic chemistry
Reactivity and mechanisms
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Summary:Important aspects of the electrochemical reduction of a series of substituted arene sulfenyl chlorides are investigated. A striking change is observed in the reductive cleavage mechanism as a function of the substituent on the aryl ring of the arene sulfenyl chloride. With p-substituted phenyl chlorides a “sticky” dissociative ET mechanism takes place where a concerted ET mechanism leads to the formation of a radical/anion cluster before decomposition. With o-nitropheyl sulfenyl substituted chlorides a stepwise mechanism is observed where through space S···O interactions play an important role stabilizing both the neutral molecules and their reduced forms. Disulfides are generated through a nucleophilic reaction of the two-electron reduction produced anion (arenethiolate) on the parent molecule. The dissociative electron transfer theory, as well as its extension to the case of strong in-cage interactions between the produced fragments, along with the gas phase chemical quantum calculations results helped rationalize both the observed change in the ET mechanism and the occurrence of the “sticky dissociative” ET mechanism. The radical/anion pair interactions have been determined both in solution as well as in gas phase. This study shows that despite the low magnitude of in-cage interactions in acetonitrile as compared to in the gas phase, their existence strongly affects the kinetics of the involved reactions. It also shows that, as expected, these interactions are reinforced by the existence of strong electron-withdrawing substituents.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja062796t