FORMIC-ACID ANHYDRIDE - MATRIX INFRARED-SPECTRA OF 5 ISOTOPIC-SPECIES, VIBRATIONAL ANALYSIS, EMPIRICAL AND ABINITIO HARMONIC FORCE-FIELD AND THERMODYNAMIC FUNCTIONS

Argon matrix infrared spectra of formic acid anhydride (CHOOCHO, CDOOCHO, CDOOCDO, and CH18O18OCH18O) are presented. Assignments and normal coordinate analysis yield valence force constants (VFF I) reflecting a significant dependence on the conformation of the formyl groups. A similar dependence is borne out by force constants obtained from an ab initio SCF treatment. The quantum chemical force constants qualitatively confirm Badger's rule. It is shown that a second valence force field (VFF II) may be found which is in qualitative agreement with the quantum chemical force constants and also reproduces the observed frequencies just as well as VFF I. The stretching force constants appear to be enhanced for bonds which are trans to another bond. © 1979.