The results are presented for molecular dynamics simulations of liquid 18-crown-6 using different potential models. The results offer the possibility of investigating the influence of the flexibility of the dihedral angles and the effects of the united atom approach. The radial distribution functions and the correlation between the molecular separations and relative orientations are found to be rather insensitive to the specific potential model used. The relation between orientation correlations and dipole-dipole correlations on the other hand is found to be very sensitive to the flexibility of the molecule. The contributions of the dipole-dipole correlations to the dielectric constant are found to be small compared to those of the molecular dipoles. The calculated dielectric constants are very much in disagreement with the experimental one. It is believed that adding electronic polarization terms to the potential models will very much enhance the contributions of the dipole-dipole correlations to the dielectric constant without necessarily changing the molecular and structural properties.