Vibrational Spectra and Molecular Structure of Bicyclo[1.1.0]butane

The infrared and Raman spectra of bicyclo[1.1.0]butane and the infrared spectrum of its deuterated analogue were observed. The rotational structure of some infrared bands were partially resolved. If the numerical values occurring in cyclopropane and its derivatives are adopted for the related structural parameters of bicyclobutane, the spectrum is found consistent with a C2v structure with an angle between the planes of the rings of 126°±3° and a bridgehead C–C distance of 1.54±0.02 Å. A complete assignment of the fundamental vibrational frequencies of the light isotope is given.