- The improved Kolbe-Schmitt reaction using supercritical carbon dioxide
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A comparative analysis of the reactions between sodium phenoxide and CO2 under the gaseous and supercritical conditions has demonstrated the preferential effect of supercritical conditions for promoting the reactivity of CO2. A significant increase in product yield was obtained in supercritical CO2 compared to reactions undertaken in gaseous CO2.
- Iijima, Takayuki,Yamaguchi, Tatsuaki
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- Competitive measurement of rate constants for hydroxyl radical reactions using radiolytic hydroxylation of benzoate
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Hydroxyl radicals were generated from N2O-saturated phosphate-buffered saline solution (pH 7.5) by irradiation with a 3.7 TBq 137Cs source. The radicals attacked benzoate to form highly fluorescent products. The induction of fluorescence was tested in 0.002 to 2 mM of benzoate solution; the fluorescence intensity was approximately constant at benzoate concentrations more than 0.1 mM during irradiation, and increased linearly with irradiation dose up to 53 Gy tested. The major primary products detected by high- performance liquid chromatography were three monohydroxybenzoates, 2-, 3- and 4-hydroxybenzoate (HOBZ). The G-values obtained from γ-irradiation for 60 min of a 0.2 mM benzoate solution were G(2-HOBZ) = 0.97, G(3-HOBZ) = 0.48 and G(4-HOBZ) = 0.45. As the fluorescence of irradiated benzoate solution arose mostly from 2- and 3-HOBZ and the intensity of 2-HOBZ is 30 times that of 3- HOBZ, 98% of the fluorescence intensity induced was ascribed to 2-HOBZ. A hydroxyl radical scavenger competed with benzoate for hydroxyl radicals produced, and diminished the fluorescent products. A rate constant for the reaction of a scavenger with hydroxyl radical could be determined from the reduction in fluorescence intensity, using 0.2 mM benzoate and various concentrations of the scavenger. The fluorescence intensity was detectable down to 0.15 μM of 2-HOBZ produced. For various compounds, rate constants obtained in this way were similar to those measured by pulse-radiolysis.
- Motohashi,Saito
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- Effect of Polyether Linkages on the Carboxylation of Sodium Phenoxide
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In the carboxylation of sodium phenoxide under mild conditions, the crown compound or polyethers with three to five ether linkages caused carboxylation to give o- and p-hydroxybenzoic acids, but not ethers with one or two linkages.The chelation of sodium phenoxide with polyethers changed the formation ratio of isomers.
- Sakakibara, Tsutomu,Haraguchi, Kazuyo
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