VIBRATIONAL-SPECTRA, STRUCTURE, ASSIGNMENT, AND IDEAL-GAS THERMODYNAMICS OF A 3-RING MOLECULE - DIBENZOFURAN

Gas, liquid and solid-phase vibrational spectra are recorded and assig ned for the three-ring molecule dibenzofuran. The vapor-phase infrared and Raman spectra are consistent with a planar C-2v structure. The as signment of fundamentals is assisted and tested by scaling the AM1 for ce field of dibenzofuran using scale factors previously derived from b oth monocyclic and bicyclic sources. It is found that these monocyclic and bicyclic scale factors calculate the dibenzofuran fundamental wav enumbers to respective standard deviations of approximate to 17 and ap proximate to 13 cm(-1), with most of the improvement for the bicyclic scale factor calculation attributable to the nonplanar blocks. The ass ignment of fundamentals supports the majority of fundamentals previous ly assigned, although several previous ambiguities are removed. From t he assigned fundamentals, ideal-gas thermodynamics are derived using s tatistical mechanics. These values compare extremely well with those f rom calorimetry, the difference in entropy being generally less than 0 .1% of the total ideal-gas entropy and well within the combined uncert ainties of the two methods.