A geometrical and energy analysis has been performed on the isolated chain of syndiotactic polymers having the formula (-CHR-CH2-CO-)(n) where R = C6H5, (o-, m-, p-) C6H4CH3, in comparison with (-CH2-CH2-CO-)(n) with the aim of predicting the best conformations in the crystalline field. By geometrical analysis the relations between the bond and torsion angles in the main chain have been found in the framework of the tc line repetition group. The results of the conformational energy calculations show that the presence of the side groups gives rise to significant deviations from the all trans conformation. On the contrary, secondary effects on the chain conformation are found in relation to the kind of side group. All the results obtained by energy calculations are in good agreement with experimental data.