Relationship between the structure of the simple sugars and their behaviour on the paper chromatogram

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Abstract
An empirical relation-ship was discovered between the movement of the sugars (RF value) on the paper chromatogram and the molar fraction of water (N) in the solvent. The graph of log ([ 1/RF] -1) against -log N is a straight line for each sugar. The relationship holds over a wide range of solvent mixtures, the only exceptions being those containing phenols as the organic component. The relationship is given a theoretical basis in terms of the strong association of the hydroxyl groups of the sugars with the water molecules in mixed solvents containing water. The sugars separate in the same order in all solvents, except phenols. If the sugars are arranged in the form of a homomorphous series on the basis of an assumed preferential formation of a pyranose ring in soln. (furanose when pyranose is impossible) then it is found that members of each homomorphous series show close similarity in behavior on the paper chromatogram. The sequence of RF values for each group of sugars (aldohexose, aldomethylose, etc.) depends only on the configuration of the hydroxyls of the ring. The same appears to be true of the methyl glycosides. A detailed analysis was made of the contribution of each hydroxyl group to the observed RF value in the case of the aldohexoses, aldopentoses and ketohexoses. The analysis shows that if a substituent (-CH2OH) is attached to C atom 5 of the pyranose ring, the influence of a hydroxyl group on any particular C atom largely depends upon whether the hydroxyl is on the same side of the ring as the substituent or not. The effect on the RF value is different for each C atom. In the absence of a substituent (aldopentoses) or if the substituent is attached to C atom 1 of the pyranose ring (ketohexoses), it is the interaction between the hydroxyl groups on neighboring C atoms which governs the RF value, a cis disposition of hydroxyls giving a higher RF value than a trans. Sugars with a furanose ring have a much higher RF value than those with a pyranose ring. The RF values of the simple pentoses and hexoses are roughly inversely proportional to their melting points.