Electron diffraction study of the structure and internal rotation of cyclobutanecarboxylic acid chloride

Abstract

The conformational equilibrium of (CH23CH-COCl in the vapor phase was studied as part of a broader investigation of molecules in the series R-COX. It was found that the cyclobutyl derivative exists almost entirely as gauche conformers, thereby closely resembling isopropyl and differing sharply from cyclopropyl homologues. The nonplanar ring can be bent toward the -COCl substituent (axial conformation) or away from it (equatorial conformation). A coupling between the ring bending and torsional displacements is suggested by the electron diffraction intensities such that conformations on the cis side of gauche favor the equatorial ring pucker, and those on the trans side favor the axial pucker. Bond lengths, bond angles, and amplitudes of vibration were determined and found to be normal.