- Kinetic study on hydrolysis and oxidation of formamidine disulfide in acidic solutions
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Hydrolysis and oxidation of formamidine disulfide in acidic medium were investigated using high-performance liquid chromatography (HPLC) and mass spectrometry (MS) at 25 °C. By controlling the slow reaction rate and choosing appropriate mobile phase, HPLC provides the unique advantages over other methods (UV-Vis, chemical separation) in species tracking and kinetic study. In addition to thiourea and formamidine sulfinic acid, two unreported products were also detected in the hydrolysis reaction. Mass spectrometry measurement indicates these two products to be formamidine sulfenic acid and thiocyanogen with mass weights of 92.28 and 116.36, respectively. In the oxidation of formamidine disulfide by hydrogen peroxide, besides thiourea, formamidine sulfenic acid, formamidine sulfinic acid, thiocyanogen and urea, formamidine sulfonic acid and sulfate could be detected. The oxidation reaction was found to be first order in both formamidine disulfide and hydrogen peroxide. The rate constants of hydrolysis and oxidation reactions were determined in the pH range of 1.5-3.0. It was found both rate constants are increased with the increasing of pH. Experimental curves of different species can be effectively simulated via a mechanism scheme for formamidine disulfide oxidation, including hydrolysis equilibrium of formamidine disulfide and irreversible hydrolysis of formamidine sulfenic acid.
- Hu, Ying,Feng, Jiamin,Li, Yanwei,Sun, Yanyan,Xu, Li,Zhao, Yuemin,Gao, Qingyu
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experimental part
p. 235 - 241
(2012/03/22)
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- Gas-phase generation and electronic structure investigation of chlorosulfanyl thiocyanate, ClSSCN
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The chlorosulfanyl thiocyanate molecule, ClSSCN, was generated in the gas phase through heterogeneous reaction of SCl2 on the surface of finely powdered AgSCN for the first time. The reaction products were detected and characterized in situ by ultraviolet photoelectron and photoionization mass spectrometry. The molecular geometry and electronic structures of ClSSCN were investigated by a combination of PES experiment and theoretical calculations with the density functional theory and ab initio methods. It was found that the outermost electrons of ClSSCN reside in the Cl-S antibonding π orbital, predominantly localized on the sulfur atom, and the experimental first vertical ionization potential of ClSSCN is 10.20 eV. The dominant fragment SSCN + in the mass spectrum indicates that the ClSSCN cation prefers the dissociation of the Cl-S bond.
- Yao, Li,Ge, Maofa,Wang, Weigang,Zeng, Xiaoqing,Sun, Zheng,Wang, Dianxun
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p. 5971 - 5975
(2008/10/09)
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- Temperature dependence of (SCN)2?- in water at 25-400°C: Absorption spectrum, equilibrium constant, and decay
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The temperature dependence of the absorption spectrum of the formation and decay of (SCN)2?-, a well-characterized dimer anion, was investigated at temperatures from 25 to 400°C. The absorption peak was found to shift to longer wavelength with temperature (red shift), from 470 nm at 25°C to 510 nm at 400°C. The equilibrium constants K1 and K2 for the reactions SCNOH?- SCN? + OH- and SCN? + SCN- ? (SCN)2?-, respectively, were found to decrease with temperature. Due to the considerable decrease of K2 with temperature, a rise in temperature shifts the reaction in favor of SCN?, so the observed yield of (SCN)2?- at high temperatures is strongly dependent on the SCN- concentration. As the SCN? concentration could be as high as or even higher than the (SCN)2?- concentration at high temperatures, a pseudo-first-order decay of SCN? has to be taken into consideration to account for the overall decay of (SCN)2?-. Using the kinetic parameters obtained in this work and available in the literature, the decay profiles of (SCN)2?- can be well reproduced for any temperature and KSCN concentration considered. A combination of the simulation and the experimental results reveals a decrease of ∈max of (SCN)2?- with temperature; the degree is ~30percent for a rise from 25 to 400°C.
- Wu, Guozhong,Katsumura, Yosuke,Muroya, Yusa,Lin, Mingzhang,Morioka, Tomomi
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p. 4933 - 4939
(2007/10/03)
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- The one-electron reduction potential of 4-substituted phenoxyl radicals in water
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By means of pulse radiolysis the one-electron reduction potentials of twelve 4-substituted phenoxy radicals have been determined. The main reference used was the ClO2./ClO2- couple. By combining the redox potentials of phenoxyl radicals with the aqueous acidities of phenols the bond strength of the phenolic O-H bond was calculated. These values were found to be in good agreement with O-H bond dissociation enthalpies measured in the gas phase.
- Lind,Shen,Eriksen,Merényi
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p. 479 - 482
(2007/10/02)
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- THE INFRARED SPECTRA OF THE HALOGEN ISOCYANATE AND THIOCYANATE VAPOR MOLECULES
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Fourier transform infrared spectroscopy has been used to investigate the IR spectra of the XNCO (X = Cl, Br, I, CN), the XSCN (X = Cl, Br, I) and the NCNCS vapor molecules from 4800 to 400 cm-1.Vibrational frequencies have been determined for e
- Devore, T. C.
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p. 287 - 304
(2007/10/02)
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- Outer-sphere oxidation. 2. 1 Pulse-radiolysis study of the rates of reaction of the I2-. and (SCN)2-. Radical anions with the tris(2,2′-bipyridyl)2 complexes of Os(II) and Os(III)
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The rate constants at 22°C and an ionic strength of 0.1 M for the following reactions are (Chemical Equation Presented) No adduct intermediates were detected. Formal reduction potentials for the following couples under the above conditions are as follows: Os(bpy)33+-Os(bpy)32+, 0.857 ± 0.004 V; I2-·-I-, 1.063 ± 0.011 V; I2-·I2,0.172 ± 0.011 V; (SCN)2-·-SCN-, 1.331 ± 0.008 V.
- Nord, Gwyneth,Pedersen, Britta,Floryan-L?vborg, Eva,Pagsberg, Palle
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p. 2327 - 2330
(2008/10/08)
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