The enthalpy of formation of dibenzofuran and some related oxygen-containing heterocycles in the gas phase. A GAUSSIAN-3 theoretical study

Abstract

The discrepancies between the three experimental determinations of the enthalpy of formation of dibenzofuran have prompted us to carry out a theoretical study. Standard ab initio molecular orbital calculations were performed using the recently proposed GAUSSIAN-3 theory. Owing to the size of the dibenzofuran molecule, calculations were carried out at the G3(MP2)//B3LYP level. Δ_fH_m^° values of dibenzofuran and a series of related oxygen-containing heterocycles have been calculated through atomization reactions, bond separation isodesmic reactions and other isodesmic processes. The averaged calculated Δ_fH_m^° value, 12.4 ± 1.6 kcal mol⁻¹, is inconclusive, and two of the three experimental values (R. Sabbah and I. Antipine, Bull. Soc. Chim. Fr., 1987, 392; R. Sabbah, Bull. Soc. Chim. Fr, 1991, 350 and R. D. Chirico, B. E. Gamman, S. E. Knipmeyer, A. Nguyen, M. M. Strube, C. Tsanopoulos and W. B. Steele, J. Chem. Thermodyn., 1990, 22, 1075), are equally acceptable.