Polyols, complex formation with cations

S. R. Sarfati and P. Szabo, Quantitative determination with periodate of compounds subject to non-Malapradian oxidation. Part III. Cyclohexanehexols, Carbohydr. Res., 11 (1969) 571-573. S. J. Angyal, D. Greeves, and V. A. Pickles, The stereochemistry of complex formation of polyols with borate and periodate anions, and with metal cations, Carbohydr. Res., 35 (1974) 165-173. 

Ing retention of "free" water in the resin. While the Ca -form resin retained even less "free" water, polyols and ribose were strongly retained due to complex formation. It was confirmed that the best separation of hexoses and pentoses is obtained with the Ca -form resin, while for sugar alcohols and polyols, the -form was best. Specific applications of cation-exchange resin columns include the determination of low levels of monosaccharides, alditols, and cyclltols in sheep plasma on a Ca -form column with u.v. detection at 190 nm, an extension of this involving collection... 

Recently, the use of a quite small column, namely 14.0 X 2.2 cm of Dowex 50W x 4 in the Nd form eluted with water at a rate of 50mlh , has been described for the separation of D-mannitol, D-glucitol, and D-iditol. The separation is thought to be caused by the different strength of complex formation between different polyols and metal cations that depends on the relative positions of the complexing hydroxyl groups. 

Yanagihara et al. [51 ] claimed that calcium was the only metal cation which catalyzed the epimerization they tried many others but only strontium had a weak effect. A closer investigation [52] showed cations that complex well with polyols [44] all catalyze the epimerization those metals tested by Yanagihara et al. were poor complex formers. Calcium hydroxide is best suited for this reaction because it has reasonable solubUity in water and is readily available. The reaction can also be conducted in methanol in which both calcium hydroxide and the sugars have only low solubility but when they are both present, the solvent dissolves many of them, owing to complex formation. 

Poly(propylene oxide) polyols also form complexes with potassium and sodium thiocyanate. Teeters and coworkers (33) used glass transition temperatures from differential scanning calorimetry (DSC) measurements to investigate the complexation of a 3000-molecular-weight triol with these alkali metal salts. The results indicated that at least 10 ether atoms per cation were required for formation of stable complexes. 

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