Reactions of sulfur atoms. XI. Intermediacy of a hybrid .pi.-thiacyclopropane in the addition reactions to olefins and in the thermal decomposition of episulfides

Lown, E. M.; Sandhu, H. S.; Gunning, H. E.; Strausz, O. P.

doi:10.1021/ja01027a070

Cited by 59 publications

(32 citation statements)

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“…(−11 J mol −1 K −1 ) it was concluded that the cyclic structure is preserved in the “activated complex”, which was proposed to be an electronically excited state of thiirane. This excited molecule was assumed to rapidly react with another molecule of thiirane to give S 2 and two molecules of ethene 2. At pressures “well below 15 kPa” the reaction was said to be of higher order.…”

Section: Introductionmentioning

confidence: 97%

“…In the case of the most simple episulfide, that is, thiirane C 2 H 4 S ( 1 a ), the actual mechanism of this decomposition has never been studied in detail. In a short communication,2 the gas‐phase thermolysis of 1 a at a pressure of >150 Torr (15 kPa) and at temperatures below 250 °C was reported to be a first‐order reaction with an Arrhenius activation energy ( E a ) of 40 kcal mol −1 (168 kJ mol −1 ); neither a standard deviation nor a temperature was given for this value, and no experimental details were disclosed. Ethene and sulfur were the only products.…”

Section: Introductionmentioning

confidence: 99%

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The Thermal Decomposition of Thiirane: A Mechanistic Study by Ab Initio MO Theory

Steudel

Wong

2002

Chem. Eur. J.

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Using high-level ab initio MO methods, we have identified two reaction pathways with different thermodynamic and kinetic properties for the thermal decomposition of the three-membered heterocycle thiirane (C2H4S) and related derivatives. A homolytic ring opening, followed by attack of the generated diradical on another thiirane molecule, and subsequent elimination of ethene in a fast radical chain reaction results in the formation of disulfur molecules in their triplet ground state (3S2) and requires activation enthalpies of deltaH#(298) = 222 kJ mol(-1) and deltaG#(298) = 212 kJ mol(-1). This reaction mechanism would result in a first-order rate law in agreement with one reported gas-phase experiment but does neither match the experimental activation energy nor does it explain the observed retention of the stereochemical configuration in the thermal decomposition of certain substituted thiiranes. Alternatively, sulfur atoms can be transferred from one thiirane moleculeto another with the intermediate formation of thiirane 1-sulfide (C2H4S2). This molecule can either decompose unimolecularly to ethene and disulfur in its excited singlet state (1S2) or, by means of spin crossover, S2 in its triplet ground state may be formed. On the other hand, the thiirane 1-sulfide may react with itself and transfer one sulfur atom from one molecule to another with formation of thiirane 1,1-disulfide (C2H4S3), which is an analogue of thiirane sulfone; thiirane is formed as the second product. The 1,1-disulfide may then decompose to ethene and S3. In still another bimolecular reaction, the thiirane 1-sulfide may react with itself in a strongly exothermic reaction to give S4 and two equivalents of ethene. This series of reactions results in a second-order rate law and requires activation enthalpies of deltaH#(298) = 109 kJ mol(-1) and deltaG#(298) = 144 kJ mol(-1) for the formation of thiirane 1-sulfide, while the consecutive reactions require less activation enthalpy. Elemental sulfur (S8) is eventually formed by oligomerization of either S2, S3, or S4 in spin-allowed reactions. These findings are in agreement with most experimental data on the thermal desulfurization of thiirane and its substituted derivatives. Thiirane 1-persulfide (C2H4S3) with a linear arrangement of the three sulfur atoms as well as zwitterions and radicals derived from thiirane are not likely to be intermediates in the thermal decomposition of episulfides.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

The Thermal Decomposition of Thiirane: A Mechanistic Study by Ab Initio MO Theory

Steudel

Wong

2002

Chem. Eur. J.

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“…Further steps are insertions of the silylenes into Si-H bonds of trisilane and thermolytic products and dehydrogenation, both yielding hydrogenated silicon. The gas-phase thermolysis of thiirane, feasible below 520 K, gives rise to ethylene and sulfur, has a low activation energy (168 kJ/ mole) [39] and occurs [40] Fig. 7.…”

Section: Plausible Reactions In the Gas Phasementioning

confidence: 99%

IR laser-induced co-decomposition of trisilane and thiirane for deposition of polycarbosilthiane films

Pola

Urbanová

Santos

et al. 2008

Journal of Analytical and Applied Pyrolysis

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“…Recent studies of the pyrolysis of eis-and foz7tf-2,3-dideuteriothiirane oxide indicate that deuterated ethylenes are formed with 95% retention of stereochemistry (Aalbersberg and Voll hardt, 1977). The biradical intermediate [ · CHDCHDSO · ] is suggested to be stereochemically rather rigid, akin to the π-thiacyclopropane radical pro posed in thiirane decomposition (Lown et al, 1968). Alternatively there may be a significant contribution of a concerted process to thiirane oxide de composition (Aalbersberg and Vollhardt, 1977).…”

Section: /-C 4 H 9 S-o-s/-c 4 H 9 or I-c 4 H 9 S(0)s(0)/-c 4 Hmentioning

confidence: 99%

Sulfur-Containing Radical

1978

Organic Chemistry: A Series of Monographs

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Reactions of sulfur atoms. XI. Intermediacy of a hybrid .pi.-thiacyclopropane in the addition reactions to olefins and in the thermal decomposition of episulfides

Cited by 59 publications

References 1 publication

The Thermal Decomposition of Thiirane: A Mechanistic Study by Ab Initio MO Theory

The Thermal Decomposition of Thiirane: A Mechanistic Study by Ab Initio MO Theory

IR laser-induced co-decomposition of trisilane and thiirane for deposition of polycarbosilthiane films

Sulfur-Containing Radical

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