Conformational Studies by MNDO Molecular Orbital Method on Model compounds of Aromatic Polyesters

MNDO conformational energy calculations have been performed on two model compounds of aromatic polyesters showing nemstic mesophases CH₃COOC₆H₄OCOCH₃ （mol. I ） and CH₃COOC₆H₃ （CH₃）OCOCH₃（mol. I）.
Maps of the conformational energy as a function of pairs of torsion angles shows that two model molecules have the minimum energy conformations when the two OCO groups are twisted in the opposite sense about 90° from the plane of the benzene ring.
By maps we obtain due to substitution the H atom of the aromatic ring by a CH₃ group, the conformational energy map of the mol. I is different markedly from the energy map of the mol. I . But the positions of the minimum energy conformation of two model molecules are almost the same.