Browsing by Author "Deuchar, James A."

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    Adsorption of Phenols from Non-polar Solvents on to Activated Alumina
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Davis, Keith M. C.; Deuchar, James A.; Ibbitson, Douglas A.
    A series of p-substituted phenols have been adsorbed from benzene solution on to activated alumina. The limiting adsorption values are found to be similar in magnitude when the p-substituent is small in size, and it is concluded that an almost complete monolayer of the phenol is formed, benzene being mostly excluded from the adsorbed phase at saturation. An affinity of adsorption, K, is defined in terms of an ideal model of adsorption at the solid/solution interface and it is found that in general K increases with increase in σ, the Hammett p-substituent constant. Composite adsorption isotherms have been constructed for the adsorption of phenol from a series of non-polar solvents whose reactivities are characterised by their ET values. The ET value is a molar transition energy calculated from the position of the absorption maximum in the visible spectrum of 4-(1-pyridinio)phenolate. The isotherms determine, qualitatively, the order of solvent/surface reactivity as cyclohexane < carbon tetrachloride < benzene < tetrahydrofuran < dioxan. The trend of K with ET is not so clearly established as in the case of the adsorption on silica gel, the affinity of phenol for alumina being strong in all solvents.
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    Adsorption of Phenols from Non-polar Solvents on to Silica Gel
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (6), 1973) Davis, Keith M. C.; Deuchar, James A.; Ibbitson, Douglas A.
    A series of p-substituted phenols have been adsorbed from benzene solution on to silica gel. With the exception ofp-t-butylphenol, limiting adsorptions of the solutes are almost equal in magni tude and suggest a solute-solvent molecular ratio on the silica surface of 1 : 1. An index of adsorption Ki, is defined in terms of an ideal model of adsorption at the solid-solution interface and log is found to decrease linearly with increase in a, the Hammett p-substituent constant. Composite adsorption isotherms have been constructed for the adsorption of phenol from a series of non-polar solvents whose reactivities arc characterised by their Ey values. The isotherms deter mine, qualitatively, the order of solvent/surface reactivity as n-hexane < cyclohexane < carbon tetrachloride < toluene < benzene. Quantitatively log A?! is found to decrease linearly with increase in solvent ET value.