Carbon isotope effects in Cu(I)-CO complex systems

The C-13 isotope fractionations in the exchange reaction (CO(g))-C-13 + (CO)-C-12-Cu(I)((l)) reversible arrow (CO(g))-C-12 + (CO)-C- 13-Cu(I)((l)) were experimentally determined for a chemical system consisting of H2O and CH3OH solvents and NH4Cl, NH4OH and HCl solutes at ambient temperature unde r a pressure of 9.5x10(4) Pa. The heavy isotope component, C-13, was found to be enriched in the CO-Cu(i) complex in the solution phase. Both CO solub ility and the isotope separation factor alpha were found to increase with d ecreasing temperature in all Cu(i)Cl solutions. An isotope separation facto r of 1.023 and concentration of CO absorption of 1.2 M were obtained for an aqueous solution composition of 1.5 M Cu(i)Cl, 0.75 M NH4Cl, 7.0 M NH4OH a t a temperature of 8.5 degrees C. The enthalpy and entropy changes in isoto pe exchange reactions were calculated from the temperature dependence of th e isotope separation factor. In addition, the experimentally determined iso tope separation coefficients (epsilon=ln alpha) were found to be well fitte d by the equation epsilon=a/T+b/T-2, and the values of a and b were obtaine d for both experimental systems of aqueous solutions and methanol-water mix ed solutions. The isotope exchange reaction was seen to reach an equilibriu m state within 1 min at a stirring speed of 4000 rpm.