MICROWAVE-SPECTRUM, MOLECULAR-GEOMETRY, RING BENDING POTENTIAL FUNCTION, AND ELECTRIC-DIPOLE MOMENT OF 3-BICYCLO[3 1 0]HEXANONE

The rotational spectrum in the vibrational ground state of 3-bicyclo[3.1.0]hexanone and in each of the states vB=1 through to u'B=5 associated with the bending mode of the five-membered ring has been observed and analyzed to give rotational constants. Rotational constants have been derived likewise for the vibrational ground states of the isotopic species [13C1]-, [13C2]-, and [13C6]-3-bicyclo[3.1.0]hexanone studied in'natural abundance and the species [18O]-3-bicyclo[3.1.0]hexanone after isotopic enrichment. rs coordinates for the substituted atoms were therefore obtained and, if the assumptions of rs (C=O)=1.210 Å (as in cyclopent-3-enone) and of coplanarity of the atoms O, C3, C2, and C4 are made, the principal axis coordinates of the remaining heavy atom (C3) can be established. The following, essentially rs, structure for the heavy atom skeleton of 3-bicyclo[3.1.0]hexanone then results:[formula omitted] From Stark effect measurements, the values reported for the electric dipole moment components are[formula omitted] The far-infrared spectrum of 3-bicyclo[3.1.0]hexanone observed in the range 50-150 cm-1 allows the fundamental and hot bands associated with the bending mode of the five-membered ring to be assigned. A one-dimensional treatment of this mode in terms of the reduced ring bending coordinate Z establishes that the observed spectrum for the bending mode is best described by the potential energy function [formula omitted]. © 1978, American Chemical Society. All rights reserved.