Contour Analysis of Carbonyl Infrared Bands in Solution

Abstract

A Perkin-Elmer model £21 infrared grating spectrometer was modified for digital recording of spectra. The isolated carbonyl, band contour of very dilute 3- and 2-nentanone solutions was investigated. "Goodness of Fit" criteria indicated that the band shapes could not be considered within experimental uncertainty to be Lorentzian. Asymmetry in the bands was observed to be greater in the 2-pentanone solutions. Decomposition of the carbonyl bands into two Lorentzians by a multivariable minimization method produced two bands which satisfied reasonably well the "Goodness of Fit" criteria. Conformational heterogeneity or hot bands are suggested as possible explanations for the origin of the carbonyl band asymmetry.