The electrochemical and chemical oxidation (by hindered o-benzoquinones or NOCIO4) of H2S in nonaqueous solutions (MeCN) proceeds with the donation of one electron. The formation of the unstable radical cation of hydrogen sulfide was detected by cyclic voltammetry. The radical cation decomposes to form H + and the HS' radical. The generation of the hydrogen sulfide radical cation was confirmed by ESR spectroscopy in a frozen Freon matrix. The possibility of using the hydrogen sulfide radical cation in the synthesis of organosulfur compounds under mild conditions was studied.Key words: radical cation of hydrogen sulfide, oxidative activation, cyclic voltammetr3', ESR spectroscopy, reaction mechanism.All hydrogen sulfide in natural gas is usually burned for the preparation of elemental sulfur.t,z The possibilities of using hydrogen sulfide 3 are wider than this process alone. Hydrogen sulfide, as Scheme I demonstrates, is a valuable raw material for syntheses of various organosulfur compouqds. The variety of products of organic synthesis involving H2S and wide use of them in various areas of chemical industry emphasize the urgency of studying the mechanism of reactions in which hydrogen sulfide acts as the main reactant. These reactions are usually difficult to perform because of the low reactivity of molecular hydrogen sulfide. As a rule, all of them proceed at elevated temperature and pressure or under UV irradr SchemeIn this work, we consider a new method for the preparation of organosulfur compounds from hydrogen sulfide under relatively mild conditions with the electrochemical and chemical activation of this reagent. Results and DiscussionAccording to the data of cyclic voltammetry (CV), in nonaqueous media (MeCN) hydrogen sulfide is electrochemically oxidized in the one-electron irreversible step at a potential of 1.6 V. The sedondary wave exhibits the peak of proton reduction (Epc = -0.2 V) identified by the addition of anhydrous perchloric acid (Fig. 1, a). Microelectrolysis of hydrogen sulfide at 1.8 V results in the appearance of an anodic peak at zero potential. This peak corresponding to the formation of hydrogen polysultides (Fig. I, b) was identified by the addition of a freshly prepared solution of polysulfans. Opalescence of the solution due to the precipitation of elemental sulfur was obserced during microelectrolysis.Diffusion is the limiting step of hydrogen sulfide oxidation in nonaqueous media because the maximum current as a function of the square root of the potential sweep rate (v = 0.5--100 V s -~ ) and the calibrating plot are linear and pass through the origin, 4 The data presented above suggest that the electrochemical oxidation Published in
The presence of hydrogen sulfide in fuel oil is a danger, since hydrogen sulfide is concentrated in the gas phase of tanks, vessels and tanks truck that when carrying out operations of drainage-fulness can lead to an excess of its MAC in air and to the creation of explosive mixtures. The concentration of H2S in fuel oil produced at refineries is 20-500 ppm, while its content in commercial fuel is limited to 10 ppm. Analytical methods of definition of concentration of a hydrogen sulfide in oil products are considered. Industrial and promising technologies for reducing H2S in fuel oil, their main merits and demerits are presented. The possibilities of low-energy wave technologies in the refinement of petroleum and oil products and mechanisms of action of ultrasound and constant magnetic field on oil disperse systems are shown. The hydrogen sulfide extracted from fuel oil neither on volumes, nor on concentration can't be used as independent raw materials for processing into elemental sulfur in the Claus process and is a toxic by-product. At the same time, hydrogen sulfide-containing wastes can serve as valuable raw materials for the production of wide range of useful organic compounds (antioxidants, drugs, pesticides, fungicides) in electrochemical processes. In processes of low-tonnage chemistry, electrochemical processes are relevant. As a result of anode or cathode activation of a hydrogen sulfide (alkanethiols) at ambient temperature and atmospheric pressure the thiyl (alkylthiyl) radical is formed. Along with products of a thiolation of organic compounds are formed also mono - di - and the trisulphides having higher biological activity and lower toxiferous in comparison with thiols. The competitiveness of electrosynthesis is very high, it is considered as processes of waste-free production as at the heart of it ecologically focused idea of "green chemistry" is concluded.
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