Knowledge Bank

In solid solutions of large molecules of biological interest such as chlorophylls and proteins, the infrared spectra show large structureless bands. These characteristics are due to over lapping bands.1 To separate the components in the massive absorptions it is necessary to know the band shapes and bandwidths of the functional groups involved in the absorption. We have used acetone in $CS2$ solutions as a model system for the ketone carbonyl bands of solid solutions of chlorophyll. The spectra at several concentrations were obtained and concatenated to obtain a spectrum free of noise. Three bands were readily observed: one band was a combination band which was in Fermi resonance with the second band assigned to the ketone carbonyl, the third band was an isotope satellite. Two more broader and weaker bands were situated on each side of the carbonyl band. These bands were assigned to the combination of the carbonyl band with the rotational-translational band situated in the far ir. After Fourier deconvolution of the bands situated in the carbonyl region, several satellite bands were observed. These were assigned to different conformers of the molecule. Using the simulation technique of Pitha and Jones we have fitted the bands to determine the relative concentration, the bandwidth and band shape of each conformers. Complications arising from the Fermi resonance will be discussed