Interaction of Hydrochloric Acid with Cyclodextrin

Abstract The first order rate constant for the hydrochloric acid catalyzed hydrolysis of β‐cyclodextrin increases during the reaction, because the α‐1,14‐bonds present in the macrocycle and in linear dextrins (formed by opening of the macrocycles) are split at different rates. The activation energy for hydrolysis of the glycosidic bond of maltose is 30,5 kcal/mole, while the opening of the cyclodextrin macroring is characterized with a value of 34,2 kcal/mole. At lower temperatures and higher HCl concentrations a rather stable crystalline HCl‐cyclodextrin complex is formed with good yield. This complex contains 1,8 molecules of HCl per cyclodextrin unit. After storage at room temperature for one year it still retains 1 mole of HCl. Storing the product in sealed vials for one year leads to no change in the composition.