Uncatalyzed and general acid catalyzed decomposition of alkyl xanthates and monothiocarbonates in aqueous solutions

Millican, Robert J.; Angelopoulos, Maria; Bose, Anita; Riegel, Bram; Robinson, Darlyne; Wagner, Carol K.

doi:10.1021/ja00349a045

Cited by 14 publications

(9 citation statements)

References 5 publications

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“…For completeness, Mechanism 1 also includes the contribution by the non-oxidative decomposition of ETC Ϫ to form carbonyl sulfide (COS) (k 9 ). This was determined to be 1.5 × 10 Ϫ5 s Ϫ1 , which compares closely with that measured 20 for O-methyl thiocarbonate of 2.7 × 10 Ϫ5 s Ϫ1 . The non-oxidative decomposition pathway is, however, only a minor component of ETC Ϫ decay under the conditions used in this study.…”

Section: Resultssupporting

confidence: 83%

Kinetics and mechanism of the oxidation of ethyl xanthate and ethyl thiocarbonate by hydrogen peroxide

Silvester

Truccolo²,

Hao

2002

J. Chem. Soc., Perkin Trans. 2

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Kinetic studies on the oxidation of ethyl xanthate (O-ethyl dithiocarbonate) by hydrogen peroxide have been conducted for a range of ethyl xanthate and hydrogen peroxide concentrations over the pH range 8-12. The initial reaction product is a canonical form of O-ethyl S-oxodithiocarbonate. Further oxidation leads to a bifurcation in the reaction pathway, with the formation of either O-ethyl thiocarbonate or a canonical form of O-ethyl Soxoperoxydithiocarbonate. The partitioning of the reaction between these alternative reaction paths is pH dependent, with the proportion directed towards the O-ethyl thiocarbonate branch increasing over the pH range 10 to12. Further oxidation of O-ethyl thiocarbonate leads to the formation of O-ethyl S-oxothiocarbonate (or a canonical form thereof ), analogous to the initial oxygen addition to ethyl xanthate. For both reaction branches the ultimate sulfur-containing product is sulfate. Apart from the process controlling the bifurcation, the reaction kinetics can be modelled as a series of bimolecular oxygen addition steps. This kinetic model is supported by hydroxyl radical scavenging experiments (using tert-butyl alcohol) that suggest no involvement by OH ؒ . The pH dependence of the rate parameters indicates that reaction occurs exclusively with H 2 O 2 rather than HO 2 Ϫ , consistent with the expected nucleophilic attack at the peroxide oxygen. The process controlling the partitioning between the two alternative pathways is proposed to originate from an oxygen addition adduct of O-ethyl S-oxodithiocarbonate. This work reveals that a range of potential metal ion complexants may be produced in the industrial application of xanthates (primarily sulfide mineral extraction, but also including viscose rayon production and pesticide manufacture), and that the environmental chemistry of these reagents is more complex than has been previously appreciated.

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Section: Resultssupporting

confidence: 83%

Kinetics and mechanism of the oxidation of ethyl xanthate and ethyl thiocarbonate by hydrogen peroxide

Silvester

Truccolo²,

Hao

2002

J. Chem. Soc., Perkin Trans. 2

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“…Any base (or bases) B present in solution deprotonates the zwitterion, which results in thiocarbamate formation. Some subsequent works are in agreement with this mechanism [8][9][10][11]. Assuming that the zwitterion is a reactive intermediate whose concentration is small and quickly reaches a steady state value, the rate of reaction of COS is given by…”

Section: Reaction Mechanismmentioning

confidence: 53%

Kinetics of carbonyl sulfide reaction with alkanolamines: A review

Vaidya

Kenig

2009

Chemical Engineering Journal

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“…The Brönsted slopes for k H 2 O are β lg = −1.1 and −1.3 for the monothio and dithio carbonates, respectively, which were interpreted as a late TS in the decomposition reaction . The general acid coefficients are α = 0.57−0.58 and 0.8−0.9 for the monothio and dithio compounds, respectively .…”

Section: Thiocarbonatesmentioning

confidence: 98%

“…Inverse SKIE for k H are observed for both series of substrates. The high Brönsted α value for O- ethyl dithiocarbonate coupled with a large inverse isotope effect ( k D / k H = 2.53) places this reaction in the borderline between specific acid-catalyzed and concerted mechanisms, although the latter is favored …”

Section: Thiocarbonatesmentioning

confidence: 99%

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Kinetics and Mechanisms of Reactions of Thiol, Thiono, and Dithio Analogues of Carboxylic Esters with Nucleophiles

1999

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ContentsI. Introduction 3505 II. Thioesters 3506 A. Thioalkanoates 3506 B. Thiobenzoates 3510 III. Thiocarbonates 3512 IV. Isothiocyanates 3516 V. Thioaldehydes and Thioketones 3517 VI. Thioamides and Thioureas 3517 VII. Thiocarbamates 3519 VIII. Halogenothioformates and Related Compounds 3520 IX. Conclusions 3522 X. Acknowledgments 3523 XI. References 3523 † In this review, the generic terms thioesters, thiocarbonates, thiocarbamates, and halogenothioformates will be used to comprise the corresponding thiol, thiono, and dithio derivatives.

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Uncatalyzed and general acid catalyzed decomposition of alkyl xanthates and monothiocarbonates in aqueous solutions

Cited by 14 publications

References 5 publications

Kinetics and mechanism of the oxidation of ethyl xanthate and ethyl thiocarbonate by hydrogen peroxide

Kinetics and mechanism of the oxidation of ethyl xanthate and ethyl thiocarbonate by hydrogen peroxide

Kinetics of carbonyl sulfide reaction with alkanolamines: A review

Kinetics and Mechanisms of Reactions of Thiol, Thiono, and Dithio Analogues of Carboxylic Esters with Nucleophiles

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