Analysis of the Structure of the Bands in the IR Spectrum of β-D Glucose by the Regularized Method of Deconvolution

Abstract

Deconvolution of the IR absorption spectrum of β-D glucose in the spectral range 1500–450 cm⁻¹ has been carried out. The results of the deconvolution were compared with the IR and Raman spectra recorded at room and low temperatures and with the data obtained by theoretical calculations for the frequencies of the normal vibrations of the β-D glucose molecule in the crystalline state. It is shown that deconvolution of the IR spectra recorded at room temperature makes it possible to separate the bands observed experimentally only at a very low temperature of the sample and a number of components that were not resolved earlier. The number of bands separated on deconvolution of the IR spectra of β-D glucose in the spectral range 1500–450 cm⁻¹ is more than twice the number of visible absorption maxima in the usual spectrum. The results of deconvolution of the IR spectrum of β-D glucose are in good agreement with the data of theoretical calculations for the frequencies of the normal vibrations of the β-D glucose molecule in the crystalline state. The existence of the factor-group (Davydov) splitting of a number of frequencies of the nondegenerate fundamental vibrations of molecules in a crystal cell has been revealed in the IR spectrum of β-D glucose. It was concluded that the model of an isolated molecule is insufficient for detailed theoretical interpretation of the vibrational spectra of carbohydrates.