Normal-Coordinate Analyses of Hydrogen-Bonded Compounds. V. The Enol Forms of Acetylacetone and Hexafluoroacetylacetone

Abstract

The infrared spectra of the enol forms of acetylacetone, hexafluoroacetylacetone, and their deutero analogs have been measured from 4000 to 70 cm⁻¹. Normal‐coordinate analyses have been carried out to estimate the force constants as well as to make theoretical band assignments. The bands at ∼2750, 1460, 945, and 230 cm⁻¹ of nondeuterated acetylacetone have been assigned to the vibrations originating in the O–H···O system. The corresponding force constants are: O–H stretching, 4.00; O–H···O in‐plane bending, 0.05; OH···O stretching, 0.30 mdyn/Å. Similar calculations have also been carried out for hexafluoroacetylacetone and its deutero analog. The effect of the substituent on the chelate ring has been discussed by comparing the results obtained for these two molecules.