INFRARED INTENSITIES - BICYCLO[1.1.1]PENTANE - A NORMAL-COORDINATE ANALYSIS AND COMPARISON WITH [1.1.1]PROPELLANE

The infrared and Raman spectra of bicyclo[1.1.1]pentane and of its 1-d1 and 1,3-d2 isotopomers were determined, and the intensities of the infrared bands were measured. An analysis of the rovibronic structure of nu17 and nu18 in the d0 and d2 bicyclopentanes yielded two moments of inertia that can be used in structural studies. A new vibrational assignment was made with the help of the spectrum calculated using the 6-31G* basis wt. A normal-coordinate analysis was carried out, and the infrared intensities were converted to atomic polar tensors and to dipole moment derivatives with respect to symmetry coordinates. The results of this investigation are compared with similar data obtained previously from [1.1.1]propellane. Bicyclo[1.1.1]pentane was found to resemble cyclobutane whereas [1.1.1]propellane resembles cyclopropane.