Conformational study of dibenzo[d,g][1,3]dioxocin-12-one by vibrational spectroscopy and molecular mechanics

Abstract

Two of the four possible dibenzo [d,g][1,3]dioxocin-12-one conformers are identified in solution from IR and Raman spectra. The experimental enthalpy difference between boat-chair (BC) and twist T) conformers of 0.7 kcal mol- is obtained from temperature dependent IR spectra. Structural parameters and the potential energy difference (1.4 kcal mol-1) for these conformers are calculated by molecular mechanics. Band shape simulations and normal coordinate analysis are applied when they are necessary for interpretation of the experimental results. The conformational equilibria seems to be non-typical for cyclic systems with two planar units in 1,4 position. © 1991.