The Relation Between the Infrared Spectra and Structure of Carbohydrates and Related Compounds

Citation

Burket, Stanley Campbell (1950) The Relation Between the Infrared Spectra and Structure of Carbohydrates and Related Compounds. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/eeq1-8d09. https://resolver.caltech.edu/CaltechTHESIS:06242025-143842219

Abstract

Historically the investigation reported in this thesis was initiated as a study of the relation between the infrared spectra and structure of cellulose. It was soon found, however, that the large backlog of information about the infrared spectra of related compounds which would naturally be required in the study of such a complex substance was almost entirely missing. Consequently the material presented in this thesis consists principally of a study of the infrared spectra of simpler related compounds. The region of the spectrum which we have discussed is that from 7.6 to about 13μ.

The compounds which we have studied are either pyranoid carbohydrates or possess one or more of the following structural features in common with them: (1) many hydroxyl groups, (2) an oxygen-containing six-membered ring, (3) many hydroxyl groups attached to a six-membered ring. The infrared spectra of these compounds have been discussed on the basis of the tentative assumption that each atom may be assigned a fixed fractional charge and that the infrared activity of vibration may be estimated roughly by considering their forms.

The glykitols (polyhydr1c acyclic alcohols), tetrahydropyran and p-dioxane, and some cyclitols (polyhydric cyclic alcohols) are discussed in Part II. By application of the assumptions mentioned above fairly complete vibrational assignments are made for the spectral region 7 to 12.5μ for ethylene glycol, tetrahydropyran and p-dioxane. Ethylene glycol is shown to have a staggered C₂ structure rather than the flat C_2h trans structure, and new spectroscopic arguments, based on the above assumptions, are advanced against the flat D_2h and the C_2v boat structures for p-dioxane and the corresponding structures for tetrahydropyran.

The principal absorption bands of the cyclitols between 8 and 13μ are accounted for in terms of skeletal stretching vibrations only and it is inferred that this holds true for the sugars also. Scyllitol, the all-trans cyclohexanehexol, is shown to have. its hydroxyls in equatorial rather than polar positions.

In Part III the sugars are discussed, and it is shown that their structures are probably based on a somewhat strained chair-type pyranose ring. A correlation has been observed bet ween the intensity distribution. in the infrared spectral of the monosaccharides and the number of polar hydroxyls, assuming the hydoxymethyl group to be in an equatorial position. This correlation is quite good for the glucose oligosaccharides, but is not very useful for mixed oligosaccharides.

The infrared absorption spectra of animal cellulose, cellophane, starch, and some cellulose derivatives are presented in Part IV.

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