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[en] When radioactive wastes such as concentrated liquid wastes and spent ion exchange resins are solidified in a vessel by using a solidifying agent, either of materials reacting with carbonate ions to form insoluble precipitates or an insoluble carbonate compounds are caused to be present together with the wastes, and the solidifying agent is filled in the vessel to solidify them. With such procedures, 14C-containing insoluble materials are formed by the reaction of 14C contained in the radioactive wastes and the material reacting with carbonate ions and forming insoluble precipitates, or by isotope reaction between the 14C-containing carbonate ions and carbonate ions of the insoluble carbonate compounds. Since 14C-contained in radioactive wastes can thus be converted into insoluble materials, a 14C retaining property of the solid wastes is increased by about one digit thereby capable of enhancing the safety of the solidification products compared with conventional cases. (T.M.)
[en] Polarized Raman spectroscopy has been used to measure the deuterium isotope effect, ΔpK = pK_D_2_O - pK_H_2_O, for the second ionization constant of carbonic acid in the temperature range of 25 "oC to 125 "oC, CO_3"2"- + D_2O ⇋ DCO_3"- + OD"-. Results for the light water pK dependence on temperature were compared to literature, confirming the reliability of the method. (author)
[en] Published data on dimethyl carbonate as a safe reagent and solvent in organic synthesis are generalized and analyzed. The methods of dimethyl carbonate preparation and its use as methylating and carboxymethylating reagent are considered. The attention is focused on the environmentally safe processes corresponding to the green chemistry principles.
[en] The mechanisms of noncatalytic and autocatalytic addition–elimination reactions of dimethyl carbonate with methylamine have been studied in terms of wB97XD/6-311++G(df,p), M06/6-311++G(df,p), and PBE0/6-311++G(df,p) quantum chemical methods, and thermodynamic and activation parameters of these reactions have been calculated. The rate-determining stage is the formation of tetrahedral carbon intermediate. The addition–elimination mechanism is preferred over the autocatalytic SN2 mechanism determined by enhanced donor–acceptor and acid–base properties of amine complexes with alcohol associates in comparison to amines.