The Structure of Cation-Carbohydrate Complexes

A compound may not possess one of these complexing sites in its most stable conformation but only in a less favored one it may then form a complex after having changed into the latter. An example is -D-ribopyran-ose 45,46 aqueous solution, this sugar is a conformational mixture of 75% 

If the difference in free energy between the non-complexing and the complexing conformation is large, complex-formation will not take place, as shown by the examples of w o-inositol and c -cyclohexane-l,3,5-triol. Complex-formation then does not supply sufficient free energy for the conformational change to take place. 

All of the alditols form complexes with cations, but the extent of complex-formation varies considerably, the Af, values of hexitols ranging from 0.24 

If one of the three hydroxyl groups is replaced by a methoxyl group, complexing still occurs, but it is somewhat weaker (Section III,4). If all three hydroxyl groups are methylated, complex formation becomes n igible.  

Electrophoretic mobility shows that even two consecutive hydroxyl groups can form a complex, although a very weak one, if they can approach 

---