Browsing by Author "Ah-Sing, Eric"

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    Heats of Solution of Electrolytes in Ethanol and Derived Enthalpies of Transfer from Water
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (02), 1978) Abraham, Michael H.; Ah-Sing, Eric; Namor, Angela F. Danil De; Hill, Tony; Nasehzadeh, Asadollah; Schulz, Ronald A.
    Heats of solution of 12 1:1 electrolytes in ethanol have been determined calorimetrically, and have been extrapolated to zero electrolyte concentration to give iXH° values for these electrolytes. Together with literature data for 9 other 1:1 electrolytes, these measurements yield a set of single ion enthalpies of transfer from water to ethanol for 11 univalent cations and 6 univalent anions. Using the assumption that A/7t‘?(Ph4As+) = A//°(Ph4B~), it is shown that small univalent cations are enthalpically more stable in ethanol than in water, but that the larger tctra-alkylammonium ions are less stable in ethanol. With the same assumption, it is also shown that all the univalent cations and anions studied are of almost the same enthalpy (within about ±0.5 kcal mol-1) in the three alcohols methanol, ethanol and 1-propanol.
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    Thermodynamics of solution of two forms of DL-α-amino-n-butyric acid in water
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (1), 1977) Abraham, Michael H.; Ah-Sing, Eric; Marks, Robert E.; Schulz, Ronald A.
    Two crystalline polymorphic forms of DL-α-amino-n-butyric acid have been obtained and have been shown to be identical to the A-form and B-form previously described by Iitaka and coworkers. The two forms differ in heat of solution and in their solubility in water. We find that for the A-form at 298 K, ΔH°s= 374 cal mol–1, ΔG°s= 1772 cal mol–1 and ΔS°s=–4.7 cal K–1 mol–1 and for the B-form ΔH°s= 1653 cal mol–1, ΔG°s= 1883 cal mol–1 and ΔS°s=–0.8 cal K–1 mol–1. Although the B-form is the stable form at 298 K, it is predicted from the above measurements that the A-form should be the stable form above ∼ 326 K.