QUANTUM-CHEMISTRY STUDY OF LI-1,2-DIMETHOXYPROPANE COMPLEXES()

Quantum chemistry studies of the lowest energy conformers of 1,2-dimet hoxypropane (DMP) complexes with Li+ ions have been carried out. Resul ts of these calculations are compared with those of our recent study o f Li+-1,2-dimethoxyethane (DME) complexes. Because of a chiral center, conformation space is more complex for DMP than for the structurally similar but achiral DME. Qualitatively similar behavior to that seen p reviously in studies of DME is found, however, including the presence of low-energy conformers containing consecutive gauche dihedrals of op posite sense and stronger interactions of the Li+ ion with conformers containing O-C-C-O gauche conformations, The former is a result of sta bilization of conformers by attractive 1,5 CH3-O electrostatic interac tions, while the latter reflects the ability of the ion to interact wi th both ether oxygen atoms. The calculated Li+-DMP complex energies an d geometries reveal that favorable interactions of the or methyl group with the ion result in a Li+-t (g) over bar t complex energy comparab le that of the Li+-tgt complex. Comparison of calculated Raman spectra with experimental measurements on DMP/LiClOs4 solutions indicates an increasingly high population of the t (g) over bar t conformer with in creasing salt content.