Polycyclic arene episulfides. Attempted synthesis, molecular orbital calculations and comparison with arene oxides

Zoller, Uri; Shakkour, Elias; Pastersky, Irine; Sklenák, Štěpán; Apeloig, Yitzhak

doi:10.1016/s0040-4020(98)00884-9

Cited by 16 publications

(13 citation statements)

References 26 publications

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“…( 2 a ) has been studied. Its ground state is a triplet, which at the HF/6‐31G* level with limited CI calculation is by 227 kJ mol −1 less stable than thiirane 1 a ;6 at the G2 level the same relative energy of 227 kJ mol −1 was obtained for 2 a at the potential energy minimum,8 while 198 kJ mol −1 were obtained at the MP3(full)/6‐31G*//HF/6‐31G*+ZPE level and 194 kJ mol −1 at the level B3LYP/6‐31G*+ZPE 9. Since these energies are of the same order of magnitude as the reported activation energy of 168 kJ mol −1 ,2 one may conclude that the homolytic ring opening is the first step in the thermal decomposition of gaseous thiirane following a first‐order rate law.…”

Section: Introductionmentioning

confidence: 68%

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: 68%

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

Steudel

Wong

2002

Chem. Eur. J.

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“…For benzo[α]anthracene-1,2-episulfide, this reaction was calculated to be exothermic (ΔH o = −30 to −33 kcal mol −1 ). 76 Because of this instability, arene episulfide is not a likely candidate as episulfide intermediate.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…In general, arene episulfides are less thermodynamically stable than the arene oxides toward the hypothetical extrusion of sulfur as S( 3 P). For benzo[α]anthracene-1,2-episulfide, this reaction was calculated to be exothermic (Δ H o = −30 to −33 kcal mol –1 ) . Because of this instability, arene episulfide is not a likely candidate as episulfide intermediate.…”

Section: Resultsmentioning

confidence: 99%

Reactive Site Model of the Reduction of SO₂ on Graphite

Humeres¹,

Debacher²,

Moreira³

et al. 2017

J. Phys. Chem. C

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Computational quantum chemistry calculations were carried out for the reduction of SO2 on graphite to produce elemental sulfur and CO2. Two models of the reactive site of graphite were used and a viable mechanism was proposed for the reaction pathways based on experimental results and known reactions. The SO2 OO approach to the zigzag edge of the model cluster yielded a sulfur-oxidized intermediate 1,3,2-dioxathiolane (1). Sulfur transfer step takes place from 1 to a neighbor benzyne site forming a reduced sulfur intermediate thiirene (2) along with a 1,3-dicarbonyl in equilibrium with the peroxide valence tautomer. The calculated barrier from 1 to thiirene 2 at 900 °C was 39.4, kcal mol–1. The peroxide tautomer isomerizes to a dioxirane intermediate that is eliminated as dioxicarbene to produce CO2. The total free energy of activation for the decarboxylation reaction at 900 °C was in the range 110.8–122.7 kcal mol–1 depending on the model (ΔG ‡ experimental, 114.3 kcal mol–1). The reduced intermediate thiirene 2 decomposes through a transport mechanism where polysulfane species with increasing number of sulfur atoms eleminate elemental S x .

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“…However, the synthesis as well as studies on the cytotoxicity and mutagenicity of some aromatic diol episulfides have been recently accomplished [78][79][80].…”

Section: Carbocations From Miscellaneous Het-ero-pahsmentioning

confidence: 99%

Quantum Chemical Studies on Ultimate Carcinogenic Metabolites from Polycyclic Aromatic Hydrocarbons

Borosky

2008

CMC

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Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants well known as mutagenic/carcinogenic agents. This review will discuss recent theoretical studies regarding the stability and reactivity of ultimate carcinogenic metabolites from PAHs, focusing on their diol epoxide and amine derivatives. Geometrical and electronic features will be analyzed in order to obtain structure-activity relationships. Charge delocalization modes (positive charge density distribution), substituent effects, and conformational aspects will be considered. Computed properties will be compared with the available biological activity data. Correlations between experimental mutagenic potencies reported in the literature and calculated reaction energies and electronic properties will be shown. Heteroaromatic compounds (aza-PAHs, thia-PAHs, and heteroaromatic amines) will also be examined. To model the important step of covalent adduct formation, calculation of the adducts resulting from bond formation between some of these electrophilic intermediates and nucleotide bases (guanine, cytosine) will be described.

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Polycyclic arene episulfides. Attempted synthesis, molecular orbital calculations and comparison with arene oxides

Cited by 16 publications

References 26 publications

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

Reactive Site Model of the Reduction of SO₂ on Graphite

Quantum Chemical Studies on Ultimate Carcinogenic Metabolites from Polycyclic Aromatic Hydrocarbons

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Polycyclic arene episulfides. Attempted synthesis, molecular orbital calculations and comparison with arene oxides

Cited by 16 publications

References 26 publications

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

Reactive Site Model of the Reduction of SO2 on Graphite

Quantum Chemical Studies on Ultimate Carcinogenic Metabolites from Polycyclic Aromatic Hydrocarbons

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Product

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Reactive Site Model of the Reduction of SO₂ on Graphite