Infrared and Raman spectroscopy of carbohydrates. Paper V. Normal coordinate analysis of cellulose I

Abstract

A normal coordinate analysis of cellulose I has been performed for an isolated chain using a valence force field and atomic coordinates from an x−ray refinement analysis. The calculated frequencies show good agreement with the observed infrared and Raman data, while the computed potential energy distribution is compatible with previous assignments, based on deuteration etc. The atomic displacements show that all the predicted modes in the region below 1500 cm−1 result from complex motions of a number of atoms or groups, rather than from single group vibrations. Most of the modes above 1200 cm−1 are localized within the residue and are very modes above 1200 cm−1 are localized within the residue and are very modes above 1200 cm−1 are localized within the residue and are very similar to those predicted for the monomer, β−D−glucose. Below 1200 cm−1 inter−residue coupling becomes more appreciable. Negligible splitting is predicted between equivalent A and B modes which suggests that the observed spectral lines are due to superimposed A and B components.