Influence of molecular structure on physical properties of chiral compounds is presented. It is shown that fluorinating of the achiral chain have great influence on physical properties of liquid crystalline phases. As an example, two compounds: (S)-(+)-4-(1-Metyloheptyloxy-carbonylbiphenyl) 4'-(6-perfluoropentanoyloxyhex-1-oxy) benzoate and (S)-(+)-4-(1-Metyloheptyloxycarbonylbiphenyl) 4'-(6-pentanoyloxyhex-1-oxy) benzoate have been selected. Phase transition temperatures and stability of these compounds have been studied by DSC calorimetry, texture observation, electrooptic measurements and dielectric spectroscopy. Based on these studies it was found that the SmC center dot -SmA(center dot) transition is a continuous one for both compounds studied.