The quantum mechanics calculations of the energetics and structures corresponding to the different representatives structural conformations of poly(vinylidene fluoride-trifluoroethylene) and poly(vinylidene fluoride-chlorotrifluoroethylene) copolymers show that the all-trans, Tp conformation, is energetically stabilized even with a chlorine substituent. The changes in the molecular arrangement associated to Tp or TGa conformations lead to significant changes in shape and electrical-chemical properties. A larger dipole moment and a orientational charge polarization were obtained for the all-trans Tp molecular structure even with a sort chlorine contamination. According to the computed results, the Curie transition temperature should be smaller in P(VDF-CTFE) than in PVDF. The fluorine NMR spectra were calculated for the different representative systems. The B3LYP functional and the 6311+G(d,p) bases set were used with the Gaussian program for carrying out the calculations.