Infrared specturm of cellulose I in relation to its structure

The infrared data for cellulose I have been critically analyzed and are found to show two parallel and four perpendicular bands in the region of OH stretching. In the region of CH stretching there are two parallel bands and four perpendicular bands. If we imagine that the chains have random phase and a twofold screw axis passes down each chain we should expect six OH frequencies. From the coordinates of O2, O3, and O6 it is shown that two modes should show parallel and four modes perpendicular dichroism. It is also shown that the mode which represents the oscillation of hydrogen atoms against oxygen atoms parallel to the line joining hydroxyl oxygen atoms O2 and O3 can produce intramolecular hydrogen bonding and should be a parallel mode. This is identified with the strong parallel band at 3350 cm.−1 Since each band should become double by virtue of symmetry and antisymmetry with respect to the screw axis we should have two parallel modes, and these are identified with parallel bands at 3350 and 3275 cm.−1. The position of the oxygen atom O6 and of hydrogen atoms H61, H62 of groups CH2 have been calculated. It is shown that the oscillating dipole moment in symmetric CH stretching mode makes an angle of 39°17′ and in the CH antisymmetric stretch an angle of 50°43′ with the fiber axis and therefore both should show parallel dichroism. These are respectively identified with bands at 2853 and 2967 cm.−1. The remaining CH vibrations belonging to the hydrogen atoms of the glucopyranose ring should show perpendicular dichroism. Four vibrations at 2945, 2910, 2897, and 2870 cm.−1 are identified with these CH vibrations. Thus all the infrared predictions are explained on the basis of the Meyer and Misch structure of cellulose I provided we assume that the chains have a random phase relationship. That a two‐fold screw axis runs along each chain direction is also in agreement with the infrared data.