Reductive dehalogenation and formation of sulfonated quinones in the aqueous reactions between various chloro-1,4-benzoquinones and sulfur(IV)

Kiss, Virág and Kecskeméti, Ádám and Hülvely, Bence Marcell and Tarczali Sarudi, Péter and Csépes-Ruzicska, Luca Judit and Mercs, Fruzsina and Tóth, Ágnes and Fábián, István and Ősz, Katalin (2023) Reductive dehalogenation and formation of sulfonated quinones in the aqueous reactions between various chloro-1,4-benzoquinones and sulfur(IV). JOURNAL OF SULFUR CHEMISTRY, 44 (6). pp. 646-665. ISSN 1741-5993

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Abstract

In this paper, the kinetic study of the reaction between substi- tuted 1,4-benzoquinones (RBQs) and Na2 SO3 (S(IV)) is presented in aqueous solutions at different pH values and reagent concentra- tions. The stoichiometry of the reaction is 1:2 RBQs:S(IV) and one equivalent of chloride ion was also detected as a product when using mono- (2-CBQ) or dichloro-benzoquinones (2,5-DCBQ; 2,6- DCBQ) as reactants. This shows that reductive dehalogenation occurs instead of simple reduction to the corresponding substituted 1,4- hydroquinones (RBQHs) and quinone bisulfites are formed, analo- gously to the addition of bisulfite ion to carbonyl compounds. Var- ious sulfonated quinones have been identified as products by elec- trospray mass spectrometry. Kinetic traces at different wavelengths were obtained by the stopped-flow technique with spectrophoto- metric detection, a kinetic fitting program (ZiTa) was used to fit a multi-step model to the data. A detailed mathematical evaluation of the reaction scheme was carried out under non-pseudo-first order conditions showing that our model can be fitted with a double expo- nential function even when none of the reagents are in large excess.

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