Abstract: Cyclodextrins (CDs) are torous-like macrocycles composed of glucopyranose units, in particular β-cyclodextrin (β-CD) consists of 7 units. They have a hydrophobic inner cavity and hydrophilic ends ("rims"). This structure allows them to form inclusion complexes with a variety of organic and inorganic molecules. CDs are widely used in practice, in particular in pharmaceuticals, analytical chemistry, catalysis and in many other fields of production and science. Since the solid phase of cyclodextrins is almost always a hydrate, the process of formation of inclusion complexes is a process of complete or partial substitution of water molecules in CDs hydrates. For directional synthesis of cyclodextrin inclusion complexes in solid–gas and solid–liquid reactions, it is necessary to know the energy parameters of the hydrate water substitution processes by guest molecules. These data are insufficiently presented in the literature and are largely contradictory. The purpose of this study is to fill this gap. Cyclodextrin hydrates of the composition β-CD nH2O (n = 11.9-0.91) were synthesized. The obtained compounds were studied by the XRD method (Shimadzu XRD-7000), which revealed a transition from a monoclinic unit cell to an orthorhombic one with a decrease in water content. DSC investigations (Setaram Sensys DSC TG calorimeter) have found an endothermic effect in the region of 182° C, which depends on the water content in the sample. The pressure of saturated and unsaturated water vapor β-CD 9.58H2O and β-CD 7.0H2O was measured by static method with glass membrane-gauge manometers [1] under conditions of quasi-constancy of composition and complete loss of water. As in the case of α-cyclodextrin hydrates studied earlier [2-3], the water vapor pressure increases in proportion to the increase in the water content in the hydrate samples. Experimental data, reduced to a single composition β-CD 1.0H2O, were approximated by the equation lnp(1/T) which was used for calculation the thermodynamic parameters (prHT and prST) of the dehydration processes of β-CD 1.0H2O. The information obtained was applied to estimate the binding energy of water molecules with the β-CD framework. The thermodynamic characteristics of the dehydration process were obtained for the first time and are valuable data not only for fundamental science, but also for the practical application of β-cyclodextrin hydrates. [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.
PHYSICO-CHEMICAL STUDY OF THE DEHYDRATION PROCESSES OF β-CYCLODEXTRIN HYDRATES
ХXIV МЕЖДУНАРОДНАЯ КОНФЕРЕНЦИЯ ПО ХИМИЧЕСКОЙ ТЕРМОДИНАМИКЕ 01-05 Jul 2024