Benzothiophene, decomposition

While some specific role of the K+ cation may account for the increased reactivity of benzothiophene with increasing amounts of KOH in the hydroxide mixture, the possible role of the total base, KOH, cannot be neglected. Potassium hydroxide is a stronger base and nucleophile in this system than NaOH is (10), and the increased basicity and nucleophilicity could account for increased reactivity toward benzothiophene decomposition. The chemical nature of ionic melts is not fully understood. While the hydroxide melts are believed to be fully dissociated (H), explanations have also been given for the formation of "quasicrystalline states (12), where order within the melt exists and dissociation is not complete. It is difficult to deduce how much independent freedom K+ and 0H have and if either the K+ cation or KOH or both are the important species. 

Benzothiophene experiments conducted at 375°C for 30 minutes with KCl-NaOH mixtures (70 30 by wt) resulted in no decomposition or desulfurization. Experiments conducted with K2C09-Na0H mixtures (70 30 by wt) resulted in complete decomposition of benzothiophene, yielding o-thiocresol and toluene as products. Relative amounts of the two products were similar to those found in experiments that used the KOH-NaOH mixture. Experiments with the KCl-NaOH mixture were repeated at longer reaction times (1 and 3 hours). After 1 hour, very little decomposition of benzothiophene had occurred. After 3-hour reaction times, the majority of benzothiophene had decomposed to toluene (4>), o-thiocresol (26 ), and tolyldisulfide (23>). While the yield of tolyldisulfide (an oxidation product of o-thiocresol) was somewhat unexpected, the longer reaction times demonstrate that KCl-NaOH mixtures can cause benzothiophene decomposition. Again, the induction or inhibition period may account for the lack of KCl-NaOH reactivity using 30-minute reaction times. 

Results of experiments with benzothiophene and pure NaOH serve to emphasize the difference between NaOH and KOH. Even at reaction times of 6 hours, no benzothiophene decomposition was observed with NaOH. These results not only emphasize the role of KVKOH but suggest that KVKOH is a necessary part of the hydroxide mixture for decomposition and ultimate desulfurization of thiophene-ring systems. 

Pseudomonas stutzeri, P. alcaligenes, and P. putida strains were isolated and proven to remove DBT, benzothiophene, thioxanthene, and thianthrene by decomposition into water-soluble substances [120],... 

Benzothiophene-1,1-dioxide (VI) in benzene solution, is converted in sunlight into a stable photodimer (Vila or VHb), which is considered to contain a central cyclobutane structure.56 196 Even though the monomer cannot be isolated on thermal decomposition of the dimer, the latter in boiling ethyl phthalate decomposes, forming sulfur dioxide and... 

Ultraviolet photolytic decomposition of benzothiophene (XII) in vacuum results in the formation of XIII and hydrogen, as well as XIV and hydrogen sulfide.95-97... 

Thiol Decomposition. As explained previously, the elimination of sulfur from benzothiophene occurs stepwise after the aromatic thiol (o-thiocresol) has formed and not in a concerted fashion from the thiophenic ring system. Extrapolation of this implies that thio-phenic sulfur in coal is eliminated by conversion to an aromatic thiol that subsequently undergoes desulfurization. Since the aromatic thiol is the apparent organosulfur species that undergoes desulfurization, it is of interest to understand the chemistry involving the elimination of sulfur from aromatic thiols. Thio-phenol was used as a model compound to examine reactions, primarily the thermal decomposition reactions that might lead to sulfur elimination. In the experiments with caustic and benzothiophene, the intermediate (o-thiocresol) most likely exists in the salt... 

The reaction of diphenyl disulfide with a variety of substituted acetylenes, promoted by thermal decomposition of di-rert-butyl peroxide, provides l,2-bis(phenylthio)ethylene adducts together with the corresponding benzothiophenes in reasonable yield ". The mechanism conceived for these transformations is depicted in Scheme 3, where the key step is the intramolecular cyclization of vinyl radicals. 

Reactions of the Side-chain of Benzothiophens.—The C n.m.r. chemical shifts in 2-benzo[ j]thenyl carbenium ions have been investigated.The thermal decomposition of 2-azidophenyl 2-(3-methylbenzo[ >]thienyl) sulphide and of 2-azidophenyl 3-(2-methylbenzo[ ]thienyl) sulphide proceeded efficiently through spiro-benzothiazolines to give (161) and (162). 5-Hydroxy-3-methyl-benzo[ ]thiophen-2-carboxylic acid is most conveniently decarboxylated by refluxing with 48% hydrobromic acid. The decomposition of benzo[/)]thiophen-2(3//)-one and of 3-diazobenzo[/ ]thiophen-2-one at high temperatures provided convenient syntheses of benzothiet and the transient benzothiet keten. The decomposition reactions were carried out in the reactor of a photoelectron spectrometer.Heterotriptycenes have been obtained from... 

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