Osmotic coefficient of aqueous solutions of cyclohexylsulfamic Acid at the freezing point of solutions.

The osmotic coefficient of aqueous solutions of cyclohexylsulfamic acid was determined by freezing point measurements up to the molality 0.65 mol kg-1. The osmotic coefficients were fitted to the Pitzer equation, and ion interaction parameters α1, ß(0) and ß(1) were evaluated. The mean ion activity coefficient of the solute was calculated, and the non-ideal behaviour of the system investigated was characterized by calculation of the excess Gibbs energy of solution, as well as the respective partial molar functions of solute and solvent. The partial molar excess Gibbs energy of the solute is negative, like the excess Gibbs energy of its solution, while the partial molar excess Gibbs energy of the solvent is positive and increases with increasing concentration of the solute. The solvation ability of water was calculated from the difference between the Gibbs energy of solution of water in solution and that of pure water, and found to be positive and small for the solute investigated, throughout the concentration range studied.

Structures of artificial sweeteners--cyclamic acid and sodium cyclamate with other cyclamates.

In the course of a study on artificial sweeteners, new crystal structures of cyclamic acid, sodium cyclamate, potassium cyclamate, ammonium cyclamate, rubidium cyclamate and tetra-n-propylammonium cyclamate have been determined. Cyclamic acid exists in its zwitterionic form in the crystalline state. The zwitterions are connected through hydrogen bonds of the N-H...O type to form two-dimensional sheets. The sodium, potassium, ammonium and rubidium cyclamates are isostructural, with the cyclamate moieties linked through hydrogen bonds into linear chains. Taking into account the connectivity through cations, two-dimensional layers with a hydrophobic surface are constructed. In tetra(n-propyl)ammonium cyclamate the large, non-coordinating cation apparently prevents the formation of chains and thereby facilitates the centrosymmetric head-to-head discrete dimeric arrangement of the cyclamate moieties.

Cholesterol complexes with tri-n-butylphosphate, tri-n-octylamine and cyclohexanone in chlorinated hydrocarbon solvents.

The hydrogen bonding interactions of moderately associated cholesterol with tri-n-butylphosphate, tri-n-octylamine and cyclohexanone in dilute solutions of tetrachloromethane, 1,2-dichloroethane and trichloromethane were studied by conventional IR spectroscopy. Information on the stoichiometry of the complexes formed was derived from least squares plots of the linearized expressions of Bjerrum's degree of system formation. The formation constants of the complexes were also determined in this way. The spectra recorded in the OH region from 3100 to 3700 cm-1 were resolved in to the bands of the cholesterol species and the complexes formed. The complexes responsible for the observed bands were recognized from the dependence of their intensity on cholesterol monomer and free base concentration and from their frequency locations. The presence of the complexes B...HO(R) and B...HO(R)...HO(R) with tri-n-butylphosphate and tri-n-octylamine was established in all of the solutions and also for the system cholesterol+cyclohexanone in 1,2-dichloroethane. On the other hand, for cholesterol bonding to cyclohexanone in tetrachloromethane, the model considering complexes with 3:1 and 1:1 stoichiometry seemed the most appropriate.