Structures of Di-p-tolyl Terephthalate (C22H18O4) and 1,4-Phenylene Di-p-toluate(C22H18O4)

Di-p-tolyl terephthalate (CA), Mr = 346.2, monoclinic, C2/m, a = 7-920 (1), b = 8.957 (1), c = 13.017 (1) A, beta= 98-425 (6) °, V= 913.4 (2) A 3, Z= 2, Dx = 1.259 (1)g cm -3, A(Cu Ka)= 1.54178, mu= 6.6 cm-1, F(000) = 364, T = 298 K, R = 0.056 for 673 reflections. 1,4-Phenylene di-p-toluate (CB), Mr = 346-2, monoclinic, P21/c, a = 6.127 (3), b = 7.555 (1), c = 19.360 (4) A, fl = 102.39 (3) °, V= 875.4 (2) A 3, z = 2, Dx = 1.313 (1) g cm -3, A(Cu Ka 0 =1.54178A, mu=6.9cm-1, F(000)=364, T= 298 K, R = 0.054 for 905 reflections. Consistent with their mesogenic properties, molecules CA and CB have a strongly anisometric shape. A common feature of their crystal packing is the almost parallel orientation of their molecular axes; layers in this direction are formed in CA but not in CB. The torsion angle C10--C9--O1--C8 of CB is 76.2 (4) ° while the corresponding angle for CA is -90 ° , owing to different conformations.