Evidence for an indirect halogen exchange in the reaction of trans‐ 2,3‐dibromo‐2,3‐dihydrobenzofuran with chloride ions
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Abstract Treatment of the title compound with chloride ions in acetonitrile leads mainly to the formation of trans ‐2,3‐dichloro‐2,3‐dihydrobenzofuran. Since a nucleophilic displacement of bromide anion by chloride anion can be excluded, a mechanism involving the equilibrium 2Cl − + Br 2 ⇋ 2Br − + Cl 2 is suggested.The behavior of OsH2Cl2(PiPr3)2 (1) in acetonitrile as solvent is studied. Acetonitrile coordinates to the metal center of 1 and promotes the dihydride−dihydrogen transformation of its OsH2 unit to give the trans-Cl2 compound OsCl2(η2-H2)(CH3CN)(PiPr3)2 (2a), which evolves to its cis-Cl2 isomer 2b. Treatment of 1 with TlPF6 in acetonitrile leads to the PF6 salt of the cis-bis(acetonitrile) cation [OsCl(η2-H2)(CH3CN)2(PiPr3)2]+ (3a), which is transformed into its trans-bis(acetonitrile) isomer 3b. The addition of Et3N to the PF6 salts of 3a,b in acetonitrile gives [OsH(CH3CN)3(PiPr3)2]PF6 (4). Reaction of 4 with 1,5-cyclooctadiene (COD) in refluxing toluene affords [OsH(COD)(CH3CN)2(PiPr3)]PF6 (5). The X-ray structures of 3b and 5 are also reported.
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Quantum yield
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The relative nucleophilicity of chloride, bromide and iodide anions in [bmim][BF4] ionic liquid has been measured by studying their reaction with methyl p-nitrobenzenesulfonate ([bmim] = 1-butyl-3-methylimidazolium cation). It has been found that iodide is the most nucleophilic halide, and that chloride and bromide have approximately equal nucleophilicities (Cl− is slightly more nucleophilic than Br−) in [bmim][BF4]. Activation energies for the reaction of chloride and bromide with methyl p-nitrobenzenesulfonate have been calculated. The relative nucleophilicity of the halides has been compared with that observed in molecular solvents and in a tetraalkylammonium tetraalkylboride ionic liquid.
Methyl iodide
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Abstract In the performance of routine determinations of serum chloride by the automated method, which depends on halide displacement of mercury from the thiocyanate to allow formation of ferric thiocyanate complex, 4 cases of bromide poisoning were detected. Experimental evidence shows the halide substitution to be an equilibrium, with higher formation constants for the heavier halide ions. As a result, the chloride determination simultaneously becomes a screen for brominism since the presence of appreciable quantities of bromide ion in serum will produce apparently high chloride values.
Thiocyanate
Mercury
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The title compound, C(36)H(30)NP(2) (+)·Br(-)·C(2)H(3)N, crystallized from a CH(3)CN/OEt(2) solution as an acetonitrile solvate. The central P-N-P angle [142.88 (10)°] is significantly larger than in the corresponding chloride and iodide structures.
Iminium
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Methyl bromide degradation in sea water can be described by a summation of the hydrolysis and chloride ion exchange reactions. Laboratory experiments covered chloride concentrations of 0.1 to 1.0 mol/1, and temperatures from 20 to 60°C. The first‐order hydrolysis rate constant is and the second‐order chloride ion exchange rate constant deduced from the experiments is At a sea water surface temperature of 21.9 °C and a chloride concentration of 0.56 mol/1, the calculated degradation half‐life of methyl bromide in sea water is 4 days. At 35 °C, τ 1/2 = 22 hr.
Degradation
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Abstract The adsorption and decomposition of acetonitrile on the TiO 2 (110) surface have been investigated with first principles calculations. Our results reveal that both CN and CC bonds of acetonitrile become weakened after adsorption. Acetonitrile behaves as an electron donor, and electrons transfer from acetonitrile to substrate is obvious. The reaction mechanism of further decomposition of acetonitrile on TiO 2 (110) surface is also investigated, and the result shows that acetonitrile can decompose into CH 3 and CN fragments and form OCH 3 and NCO groups on the TiO 2 (110) surface, which consists with the experimental results. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
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Nucleophilic Addition
Carbon fibers
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Bismuth
Cleavage (geology)
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