Dehydration of β-cyclodextrin -: An IR v(OH) band profile analysis

beta-Cyclodextrin (beta-CD) hydrate was dehydrated under vacuum at room temperature (293 K) and the changes of its IR nu(OH) band profile were observed. A curve fitting with Voigt functions to the band profile was able using information obtained from difference spectra. Four different fitting strategies gave similar band components. The behavior of the integrated intensities of these components upon dehydration was the basis for an assignment of these band components. The component a 3580 cm(-1) is due to water molecules in the beta-CD cavity and they leave very fast the macrocycle upon dehydration. Two components at 3530 and 3289 cm(-1) are assigned to OH groups retained in beta-CD despite dehydration, i.e. primary and secondary OH groups. The components at 3422 and 3185 cm(-1) may be associated with water molecules in the interstices among beta-CD molecules and linked by hydrogen bonds with them. Nevertheless, additional contributions from primary and secondary OH groups were found for these two bands. (C) 2003 Elsevier Science B.V All rights reserved.