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

Abstract

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.