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    Solute Interactions in Dilute Aqueous Solutions Part 4.—Microcalorimetric Study of Ternary Mixtures of Urea and Hydrophobic Species
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Franks, Felix; Pedley, Michael D
    Heats of dilution of urea, acetone, ethylmethyl ketone and tetrahydrofuran, and heats of mixing of urea with each of the other solutes have been measured at 25°C; the urea + acetone system was also studied at 5°C. The various enthalpic pair and triplet interaction coefficents, hij, hijj, etc. have been evaluated. The hii for the ketones and THF are positive and show a dependence on the alkyl chain length typical of the hydrophobic pair interaction, while for urea hii is negative. The cross coefficients hij are small, but positive. The triplet coefficients are generally small and of variable sign. At 5°C, all the coefficients are of a greater magnitude. The results are discussed in terms of various models for aqueous solutions of urea.
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    Microcalorimetric Studies: Enthalpies of Formation of Amino-acid and Peptide Complexes of Coppcr(ll) and Nickel(II)
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (9), 1972) Tipping, E. W.; Skinner, H. A.
    Measurements of the enthalpies of decomposition by acid at 24–25°C of a number of amino-acid and peptide complexes of CuII and NiII in solution (µ= 0.100 M) have been made using a Beckman microcalorimeter. The enthalpies of formation (from ions in solution) are derived for glycyl-glycinato(2-)copper(II), (glycylglycinato)(glycylglycinato(2-))copper(II) anion, leucylglycinato(2-)-copper(II), glycylglycinatonickel(II) cation, di(glycylglycinato)nickel(II), tri(glycylglycinato)nickel(II) anion, (glycylglycinato)(glycylglycinato(2-))nickel(II) anion, di(glycylglycinato(2-))nickel(II) dianion, glycinamidocopper(II) dication, di(glycinamido)copper(II) dication and di(glycinamido(1-))-copper(II). Equilibrium formation constants for certain of these complexes were measured from pH titration measurements. The bond strength of N→CuII in solution is greater than N→NiII whether the N atom belongs to amino or to peptide groupings.
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    Microcalorimetric Studies: Thermal Decomposition and Iodination of Metal Carbonyls
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (9), 1972) Connor, J. A.; Skinner, H. A.; Virmani, Y.
    The Calvet high temperature microcalorimeter was used to measure the enthalpies of thermal decomposition and the enthalpies of reaction with iodine vapour, of carbonyls of Mo, Mn, and Cr. ΔH°f(c) values for Mo(CO)6, Mn2(CO)10, Cr(CO)6, Mn(CO)5Cl and Mn(CO)5Br were obtained. These studies have confirmed the literature value for ΔH°f(Mn2(CO)10, c), but disagree with the currently accepted value for ΔH°f(Cr(CO)6, c). The bond dissociation energies D[(CO)5Mn—Cl] and D[(CO)5Mn—Br] were evaluated at 73 and 61 kcal mol–1 respectively: these values are ca. 20 kcal mol–1 less than the mean bond dissociation energies, D(Mn—Cl) and D(Mn—Br), in MnCl2(g) and MnBr2(g), and ca. 15 kcal mol–1 less than the dissociation energies in the diatomic molecules MnCl, MnBr.