- Chromium(III) and indium(III) 3,6-di-tert-butyl-o-semiquinolate complexes as redox mediators of hydrogen sulfide oxidation in reactions with cycloalkanes
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The electrochemical oxidation of the chromium(III) and indium(III) complexes with 3,6-di-tert-butyl-o-semiquinolate leading to the formation of active monocationic species is studied by cyclic voltammetry. The reactions of the latter with hydrogen sulfide generate the radical cation of H2S, whose fragmentation affords the proton and thiyl radical. These complexes are proposed for the first time as redox mediators for the one-pot thiolation of inert cycloalkanes C6–C8, which decreases the activation energy of hydrogen sulfide compared to that for direct electrochemical oxidation. The major products of cycloalkane functionalization involving H2S are thiols and organic di- and trisulfides. The yield of the synthesized compounds depends on the type of the mediator: the chromium(III) complex exhibits the highest efficiency in the electrocatalytic transformations.
- Berberova,Shinkar,Smolyaninov,Shvetsova,Sediki
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p. 578 - 582
(2017/09/23)
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- Mechanisms of the hydrodenitrogenation of alkylamines with secondary and tertiary α-carbon atoms on sulfided NiMo/Al2O3
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The HDN of alkylamines with secondary and tertiary α-carbon atoms (2-pentylamine, 3-methyl-2-butylamine, 3,3-dimethyl-2-butylamine, 2-methylcyclohexylamine, 2-methyl-2-butylamine) and benzylamine and the HDS of corresponding alkanethiols were studied over sulfided NiMo/Al2O3. Alkanethiols and dialkylamines were primary products in the HDS of the amines with secondary products, formed from elimination and hydrogenolysis of the alkanethiols, as confirmed by the similar alkenes/alkane ratios in the HDN of the alkylamines and HDS of the corresponding alkanethiols. 2-Methyl-2-butylamine and benzylamine reacted much faster than the amines with secondary α-carbon atoms. Methylbutenes and methylbutane were the primary products of 2-methyl-2-butylamine, and toluene was the primary product of benzylamine. This and the different methylbutenes/methylbutane ratios in the HDS of 2-methyl-2-butylamine and HDS of 2-methyl-2-butanethiol indicated that 2-methyl-2-butylamine, with a tertiary α-carbon atom, and the activated benzylamine reacted by means of an E1 mechanism. The substitution of the NH2 group by H2S led to an alkanethiol and NH3 and, thus, to total denitrogenation. Substitution by an amine led to a dialkylamine and NH3 and to 50% nitrogen removal. High partial pressures of H2S and alkylamine increased the rate of transformation of alkylamine to alkanethiol and thus, of denitrogenation. However, the rate of sulfur removal from the alkanethiol decreased.
- Zhao,Prins
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p. 532 - 544
(2007/10/03)
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- Role of hydrogenolysis and nucleophilic substitution in hydrodenitrogenation over sulfided NiMo/γ-Al2O3
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The HDS of cyclohexanethiol and 2-methylcyclohexanethiol was studied over a sulfided NiMO/γ-Al2O3 catalyst. About 66% of the thiols reacted by elimination to (methyl)cyclohexene and 33% by hydrogenolysis of the C-S bond to (methyl)cyclohexane. These values were slightly lower than those for the selectivity to methylcyclohexene and slightly higher than those for the selectivity to methylcyclohexane in the HDN of 2-methylcyclohexylamine. HDN occurred predominantly in aliphatic molecules that contained H atoms in the β position relative to the nitrogen atom by elimination of ammonia. Part of the remaining HDN occurred by nucleophilic substitution of the amine by H2S, followed by elimination of H2S from the resulting thiol and, to a lesser extent, by C-S bond hydrogenolysis, the rest of the remaining HDN occurred by direct hydrogenolysis of the C-N bond.
- Prins,Rota
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p. 195 - 199
(2007/10/03)
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