Based on the postulated 2D average molecular unit structures proposed by Zhao et al

3D conformations for the end-cuts of Athabasca bitumen pitch in Canada were created using polymethylene bridges with different lengths by the Computer Aided Molecular Design (CAMD) method. Molecular Mechanics (MM) and Molecular Dynamics (MD) computations were carried out on these conformations to determine the lowest energy structures and hence the most stable conformations.The 3D conformations and the total energy of the target molecules were intimately related. It was found that the equivalent conformations in three dimensions were quite varied even though the two-dimensional structure remained exactly the same.This meaned that simple 2D structures of macromolecules could not adequately represent their structural

physical and chemical properties. The most likely polymethylene bridge lengths within the pitch end-cut molecules were estimated from the CAMD results; a value in the range of C4 to C6 was most likely.The probability of C1 and C2 bridges was less because their total energies were comparatively high.