Microwave spectrum, equilibrium ring conformation and electric dipole moment of cyclobutane-1,2-dione

Abstract

The rotational spectrum of cyclobutane-1,2-dione consists of b-type transitions. A rigid rotor analysis of the spectrum in the vibrational ground state and in the states v_B= 1, 2 and 3 of the ring bending mode ν_B gives the following rotational constants: [graphic omitted] A planar equilibrium conformation of the heavy atoms is established on the basis of the ground state principal moments of inertia and the variation of the rotational constants with v_B. The geometry of cyclobutane-1,2-dione is discussed in terms of a model consistent with the observed ground state rotational constants.

The value for the electric dipole moment for the ground state measured using the Stark effect is 3.831 ± 0.005 D.