Calculation of Lithium Isotope Effects in Extraction Systems with Benzo-15-crown-5 and Its Derivatives

With taking into account the β-factor value of the lithium ion aqua complex found earlier, the single stage extraction coefficient of isotope separation (α) of the 6Li–7Li pair has been calculated for the extraction system containing the benzo-15-crown-5–Li+ (H2O)Cl– complex in the organic phase, which corresponds to a real extraction process. Similar calculations have been carried out for other anions, as well as for various benzo-15-crown-5 derivatives with varying the number and type of donor atoms and different substituents in the benzene ring. Quantum-chemical calculations of the vibrational frequencies of the isotopic forms of the crown ether complex were performed using the Firefly program with the RHF/6-311++G** basis set. It has been shown that the isotope separation factor in this case is lower than in the case of the anhydrous benzo-15-crown-5–Li+Cl– complex and the model benzo-15-crown-5–Li+ (H2O) complex.