The Vibrational Analysis of Cyclopentanone

Abstract

The infrared and Raman spectra of cyclopentanone, ααα′α′-d 4 -cyclopentanone, βββ′β′-d 4 -cyclopentanone and d 8 -cyclopentanone have been measured and a normal co-ordinate analysis performed based on a twisted C 2 conformation. The 36 normal vibrations were computed using a selective valence force field comprising 16 diagonal and 16 off-diagonal force constants. The 4 isotopic species provided 144 frequencies to refine 15 diagonal force constants. The initial values of the constants were transferred from a force field for cyclohexanone computed in this laboratory. The infrared and Raman spectra were analyzed in terms of the potential energy distribution coefficients categorized as group frequencies, zone frequencies, and delocalized frequencies.