Abstract: Cyclic macromolecules consisting of 6, 7, or 8 glucopyranose units, respectively are -, β- and γ-cyclodextrins (CDs). These units form hollow truncated cone cavity with hydrophilic exterior and hydrophobic interior, which can include a wide range of guest molecules, thereby forming various host-guest inclusion complexes. These inclusions may beneficially change of CD physicochemical characteristics such as solubility, thermal stability, volatility, resistance to oxidation, visible and UV light, etc. Because of these properties CDs are widely used in analytical chemistry, catalysis and also in pharmaceutical, food and cosmetic industries. Water plays an important role in CDs inclusion complexes formation, since the process of complex formation is essentially a replacement reaction of water molecules located in CD cavities by hydrophobic guest molecules. Meanwhile, quantitative data on equilibria between CDs and H2O are very scarce and contradictory, which makes it difficult to produce high-quality materials. The purpose of this work is a comprehensive study of the - and β-CD hydrates dehydration processes by static method with glass membrane-gauge manometers. The measurements have been realized in the wide intervals of temperature (313 ≤ T/K ≤ 483), pressure (0.5 ≤ р/Torr ≤ 760) and composition (CD*nH2O, 0.2 ≤ n ≤ 9.58). The accuracy of measurements for used setup was 0.5 Torr, 0.5 K and 0.01 formula units in the values of pressure, temperature and solid phase composition, accordingly [1]. 1H NMR study (Bruker AVANCE II+ 300 WB) was performed to confirm the results obtained. As a result of this study thermal stability of investigated compounds was established, temperature dependences of pressure for dehydration processes were obtained (five types of dehydration processes for -CD and two for β-CD were studied), enthalpies and entropies of dehydration were determined and Gibbs energy change in the process of binding water with CDs was calculated. On the base of information obtained the conclusions about the nature of the interactions between host (CDs) and guest molecules (water) were drown. The main results on -cyclodextrin hydrates are published in [2-3]. The accumulation of quantitative information about the dehydration processes of CDs hydrates will allow one to synthesize functional materials with desired properties in the future. [1] L. Zelenina, T. Chusova, S. Sapchenko, E. Ukraintseva, D. Samsonenko, V. Fedin, JCT. 67 (2013) 128. [2] A. Manakov, T. Rodionova, L. Aladko, G. Villevald, J. Lipkowski, L. Zelenina, T. Chusova, T. Karpova, JCT. 101 (2016) 251. [3] L. Zelenina, T. Chusova, A. Isakov, T. Rodionova, G. Villevald, A. Manakov, JCT. 158 (2021) 106424. The financial support of the Russian Science Foundation (Grant No. 24-23-00237).

Cite: Zelenina L.N. , Chusova T.P. , Rodionova T.V. , Manakov A.Y. , Sartakova A.V.
Different states of water in α- and β-cyclodextrin hydrates
ХXIV МЕЖДУНАРОДНАЯ КОНФЕРЕНЦИЯ ПО ХИМИЧЕСКОЙ ТЕРМОДИНАМИКЕ 01-05 Jul 2024