No description available.

Thesis (M.S.)--Rochester Institute of Technology, 1988. / "References": leaves 88-90.

Thesis (Ph. D.)--Johns Hopkins University, 1916. / Biography.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1979. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Johns Hopkins University, 1916. / Biography.

[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

[No abstract submitted] / Science, Faculty of / Chemistry, Department of / Graduate

The solubilisation of glucose and related sugars by thoroughly-purified phosphatidylcholine (lecithin) in benzene solution has been studied. The extent of solubilisation of the sugar has been found to depend on the concentration of lecithin, the structure of the sugar and the presence of cholesterol as a co-solute. The limiting solubility of glucose was achieved at low lecithin concentrations and corresponds to a 1:1 molar ratio of glucose to lecithin. Osmometric evidence indicated that, at higher concentrations, glucose was carried within the lecithin micelle. For other suiars, solubilisation was found to depend on the size of the sugar molecule relative to that of the lecithin micelle and on the number and acidity of its free hydroxyl groups. Enthalpy and entropy of solubilisation were determined for glucose and the results are consistent with an interaction mechanism involving hydrogen bonding via the free hydroxyl groups. Cholesterol, when present as a co-solute, competed for available hydrogen bonding sites on the lecithin molecule and thus decreased the amount of glucose solubilised, but in benzene solutions lecithin exhibited a 5:1 preference for glucose hydroxyl over cholesterol hydroxyl. In aqueous-ethanolic solutions inversion of the lecithin micelle occured and accordingly cholesterol could be solubilised. As the dielectric constant of the medium was decreased by the addition of ethanol, the micellar weight decreased and the uptake of cholesterol increased. In 90% ethanol the limiting solubility of cholesterol corresponded to a 1:1 cholesterol/lecithin ratio. In 70% ethanol the uptake of cholesterol corresponded to a 1:9 cholesterol/lecithin ratio, and this ratio was independent of lecithin concentration below 7.0 mg/ml. In media of higher dielectric constant lecithin formed an opalescent sol rather than a solution and the uptake of cholesterol decreased further, but the cholesterol/lecithin molar ratio continued to be independent of the lecithin concentration of the sol. In none of the aqueous solutions was glucose found to have any effect on the uptake of cholesterol. It is possible that these results may have biological significance.

No description available.

The solubilities of benzene, naphthalene and anthracene were measured in five binary solvent systems. These systems consised of water and one of the following water miscible organic solvents: acetone, acetonitrile, methanol, ethanol, and isopropanol. The measurements were made at intervals of 0.1 volume fractions of the organic cosolvent. Solubility data were also collected for the above solutes in mixed cosolvents. solvent systems containing three In addition, the solubilities of and six five other aromatic solutes were measured in the binary solvent systems of methanol/water and acetone/water. The data was used to test the log-linear solubility model of Yalkowsky (1981). The model predicts a linear relationship between the solubility of a solute in a binary solvent system (S(m)) and the volume fraction of cosolvent present (f(c)) log S(m) = σf(c) + log S(w) Where S(w) is the solubility of the solute in water and σ is the proportionality constant and slope of the curve. The model is easily extended to multiple mixed solvents by combining the σ values from the binary solvent systems. log (S(m)/S(w)) = Σ₁ (σ₁£₁) A method was developed to estimate σ in a given binary solvent system from the octanol-water partition coefficient of the solute. Combining this method with the generalized solubility equation of Yalkowsky to estimate S(w), allows a priori estimates of solubility in mixed solvents. Maximum deviations in the binary solvent systems studied were related to maxima in excess density. In the alcoholic binary solvent systems the minima were related to minima in the heats of mixing of the two cosolvents. The herbicide atrazine deviated dramatically from the model. The system was examined for possible changes in the crystal structure of atrazine. It was found that some crystal modification occured in the presence of mixed solvents. The rate of the change appears to be dependant on the concentration of the cosolvent. A change or modification in the crystal violates one of the basic assumptions of the log-linear model. The assumption is that the crystal contributes equally to the solubility behavior irrespective of the solvent system. It was determined that atrazine undergoes a polymorphic transition in the systems studied. It is postulated that this polymorphism is responsible for the anomolous solubility behavior observed for atrazine.