Study of the electronic structure of molecules. Barriers to internal rotation in polynucleotide chains

The barrier to internal rotation for the φ″ angle (using Olson and Flory's notation) in the sugar-phosphate-sugar complex, C10H19O8P, has been obtained from ab initio computations. The barrier height at φ″ = 60° is 4.5 kcal/mole, at φ″ = 180° is 3.3 kcal/mole and at φ″ = 310° is 7.5 kcal/mole. The corresponding minima at φ = 0°, 120° and 240° have depths of 1.3 kcal/mole, 3.3 kcal/mole and 3.1 kcal/mole, respectively. The aim of this work is to start testing the validity range of empirical or highly approximate technqiues aimed at the configurational analysis in polymeric materials. © 1973.