Comparison of Molecular Structures Determined by Electron Diffraction and Spectroscopy. Ethane and Diborane

Gas-phase average structures for the ground-vibrational state (1',) for ethane and diborane have been determined by a critical comparison of the experimental results obtained from electron diffraction (average internuclear distances ra) and those obtained from high-resolution infrared and Raman spectroscopy (rotational constants B.("'»). Experimental values have been taken from the recent literature and converted into the average structure Cr. or r",O). The ra and r",o distances determined from electron diffraction carry uncertainties less than those in the r. distances determined from rotational constants, because the latter structures are very sensitive to assumptions about the unknown isotope differences in the structures. On the other hand, the average moments of inertia from spectroscopy are much more precise than those calculated from diffraction internuclear distances. Examinations of the data have led to the following r. structures with standard errors: