Search Results
Abstract
In this study, the thermal behavior of butanediol isomers is investigated for temperatures ranging from 103 to 303 K using differential scanning calorimetry, complemented, when necessary, by polarized light thermal microscopy. The butanediol isomers display quite different thermal behaviors: for 1,2- and 1,3-isomers, glass transition is the only thermal event observed; for 1,4-butanediol, crystallization occurs on cooling even at a high scanning rate and no glass formation was detected; and for the 2,3-isomer, glass or crystal formation is dependent on the experimental conditions employed. The glass-forming ability of the isomers is correlated with data available on their molecular symmetry.
Abstract
The enthalpies, entropies and Gibbs energies of inclusion of dl-1,3-, 1,4- and meso-2,3-butanediols into α- and β-cyclodextrin cavities from ideal gas phase have been determined on the basis of newly obtained experimental data of the butanediols. The butanediol molecules are stabilised strongly in the cavities due to interactions with inner walls of the cavities. Entropies of the gaseous isomers are greatly decreased in the cavities. The largest decrease is obtained for the case of 2,3-BD. Discussions concerning the1,4-butanediol given in the preceding paper have been changed due to the adoption of new data on the butanediols.
Calorimetric study on inclusion of some alcohols into α-cyclodextrin cavities
Molecular mechanical calculation of hydration Gibbs energies
Abstract
The enthalpies of transfer 2-propanol, 1,2-butanediol (BD) and 1-hexanol from aqueous to aqueous α-cyclodextrin (CD) solutions have been determined by microcalorimetry at various mole fractions at 298.15 K. To clarify stabilities of inclusion complexes in aqueous solutions, hydration Gibbs energies calculation of inclusion complex of CD-alcohol were performed by using the molecular mechanics with the MMFF94s force field in the generalized born/surface area (GB/SA) model. The largest stabilization in Gibbs energy is obtained by the hydration (Δhyd H) of α-CD-1,2-butanediol complex among α-CD-butanediol isomers complexes.
Abstract
The enthalpies of dilution of aqueous solutions of methanol, ethanol, l-propanol, 2-propanol, 1-butanol, l-pentanol, 1-hexanol, cyclohexanol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol and poly-alcohol(cyclohexaamylose) have been determined at high dilution as a function of the mole fraction of alcohol at 298.15 K, by a rocking twin-microcalorimeter of the heat-conduction type. A smoothing equation of the enthalpies of dilution against the mole fractions of alcohols are given. The graphical comparison of experimental results with their smoothed values or literature ones, taking into account the dependence of the mole fractions, are also presented. It has been found for the aqueous solutions of shorter n-alcohols than hexanol that at very high dilution, exothermic values of molar enthalpies of dilution from a definite mole fraction of alcohols to infinite dilution with the change of mole fraction is proportional to carbon number of n-alcohols. The molar enthalpies of infinite dilution of aqueous butanediol isomers and 1-hexanol were very large. Molar enthalpies of infinite dilution of aqueous poly-alcohol (cyclohexaamylose) were endothermic.
. Boca Raton : CRC press Inc. ; 1996 1709 – 1715 . 8. Fujisawa , M , Kimura , T , Takagi , S . The enthalpic stabilisation on molecular inclusion of butanediol isomers into
