Ab initio and molecular mechanics study of 1,2-dimethoxyethane and 12-crown-4

Ab initio calculations have been carried out on a number of selected conformations of 12-crown-4. The selection of conformers was based on the low energy conformations of 12-crown-4 as obtained using molecular mechanics calculations (MM3). Extensive conformational searching within the molecular mechanics method was performed using two different approaches. The 23 lowest lying minima were submitted to ab initio calculations using different qualities of basis sets. Basis set choice was based on calculations on 1,2-dimethoxyethane and ethylene glycol as typical building blocks of the macrocycles. The highest level calculations on the crown ether are Hartree-Fock 6-31G** calculations. Results are discussed in terms of energies, geometries and intramolecular interactions. (C) 1999 Elsevier Science B.V. All rights reserved.