The determination of the conformation of molecular chains and modes of packing of poly[ethylene-l,2- bis(phenoxy)ethane-4,4'-dicarboxylate] and its chlorinated derivatives is assisted by the X-ray crystallographic analysis and energy calculations of three model compounds. Molecules of dimethyl 1,2-bis(phenoxy)ethane- 4,4'-dicarboxylate are packed in an orthorhombic crystal system, space group Pbca, with a = 6.374(4) A, b = 35.094(6) A, c = 7.124(5)A, and z = 4. The molecule has a crytallographic centre of symmetry at the centre of the CH2-CH2 bond and the two ether O atoms are oriented anti to each other. Molecules of dimethyl 1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate are packed in a monoclinic crystal system, space group C2/c, with a = 12.712(2)A, b = 7.594(1),~, c = 18.709(2)A, fl = 100.06(1) °, and z = 4. The molecule has a crystallographic two-fold axis at the centre of the CH2-CH2 bond and the O-CH2-CH2-O torsion angle of 69.9 ° makes the conformation of this part of the molecule gauche. Molecules of dimethyl 1,2-bis(2,6-dichlorophenoxy)ethane-4,4'-dicarboxylate are packed in a monoclinic crystal system, space group P21/n, with a = 4.041(2)/~, b = 12.799(1), c = 18.8528(9)/It, fl = 91.36(1) ° and z = 2. The molecule has a crystallographic centre of symmetry at the centre of the CH2-CH 2 bond and the two ether O atoms are oriented anti to each other. CH2-CH 2 bond shortenings were observed in the three model compounds. The crystal structures were compared with energy-minimized molecular structures using the semi-empirical quantum-mechanical method MNDO, giving results in substantial agreement
Посилання на статтю:
Model compounds for high modulus aromatic polyether-esters. X-ray structures and energy calculations of dimethyl 1,2-bis(phenoxy)ethane-4,4'-dica rboxylate and its chlorinated derivatives / Yukishige Kitano* and Akira Ishitani // Polymer. – 1994. – Vol 35. – P. 5179-5184.
