Publications

Abstract The standard (po = 0.1 MPa) molar enthalpy of combustion in oxygen at 298.15 K of liquid 3-methylpentane-2,4-dione (HMeacac) was measured by static bomb calorimetry as -(3353.2±1.7) kJ · mol-1. The standard molar enthalpy of formation of the crystalline copper(II) complex with 3-methylpentane-2,4-dione was determined, at the temperature 298.15 K, by solution-reaction calorimetry. The vapour pressures of the complex were measured as function of temperature by the Knudsen-effusion technique, and the standard molar enthalpy of sublimation Δg crHo m(396.70 K)/(kJ · mol-1) = 130.7 ± 1.0, was derived by the Clausius-Clapeyron equation. From this value, the standard molar enthalpy of sublimation was calculated as Δg crHo m(298.15 K)/(kJ · mol-1) = 135.6 ± 1.0. Measurement of the standard molar enthalpy of sublimation using a direct microcalorimetric method, confirmed the value from the Knudsen technique.

Abstract Using a static-bomb combustion calorimeter, the standard (p° = 0.1 MPa) molar enthalpy of combustion at the temperature 298.15 K of 3-nitrophenol was determined: - ΔcH°m(cr)/(kJ·mol-1) = 2870.0±1.5. The vapour pressure of the crystals was measured, as a function of the temperature T, by the Knudsen-effusion technique and the standard molar enthalpy of sublimation at T = 323.13 K was derived by the Clausius-Clapeyron equation: Δg crH°m(323.13 K)/(kJ·mol-1) = 98.92±0.58. From this value the standard molar enthalpy of sublimation at T = 298.15 K was calculated as Δg crH°m(298.15 K)/(kJ·mol-1) = 100.2±0.6.

Abstract The standard (p(empty set) = 0.1 MPa) molar enthalpies of formation of the following crystalline copper(II) amino acid complexes were determined at 298.15 K by solution-reaction calorimetry: DELTA(f)H(m)empty set[Cu(gly)2, cr] = - 943.7 +/- 1.3 kJ mol-1; DELTA(f)H(m)empty set[Cu(ala)2, cr]= - 1003.7 +/- 1.5 kJ mol-1; DELTA(f)H(m)empty set[Cu(val)2, cr] = - 1124.1 +/- 2.2 kJ mol-1; DELTA(f)H(m)empty set[Cu(leu)2, cr] = - 1177.8 +/- 2.1 kJ mol-1; DELTA(f)H(m)empty set[Cu(isol)2, cr] = - 1156.3 +/- 1.8 kJ mol-1; DELTA(f)H(m)empty set[Cu(Phgly)2, cr] = - 772.3 +/- 1.9 kJ mol-1; DELTA(f)H(m)empty set[Cu(Phala)2, cr] = - 831.8 +/- 2.6 kJ mol-1. The results suggest a linear correlation between the standard molar enthalpies of formation of the crystalline copper(II) amino acid complexes and those of the corresponding crystalline amino acids. Estimations of the standard molar enthalpies of sublimation of the copper(II) amino acid complexes are presented. The total binding energy between the copper(II) and the amino acid ligand is derived and compared with the corresponding parameter for copper(II) acetylacetonate.

Abstract The standard (p(empty set) = 0.1 MPa) molar enthalpies of formation of the following crystalline nickel(IU) amino acid complexes were determined, at 298.15 K, by solution-reaction calorimetry: DELTA(f)Hm(empty set([Ni(gly)2, cr] = - 994.2 +/- 1.8 kJ mol-1; DELTA(f)H(m)empty set[Ni(ala)2, cr] = - 1072.4 +/- 2.3 kJ mol-1; DELTA(f)H(m)empty set[Ni(val)2, cr] = - 1173.7 +/- 2.5 kJ mol-1; DELTA(f)H(m)empty set[Ni(leu)2, cr] = - 1243.4 +/- 2.7 kJ mol-1; DELTA(f)H(m)empty set[Ni(isol)2, cr] = - 1224.1 +/- 2.1 kJ mol-1; DELTA(f)H(m)empty set[Ni(Phgly)2, cr] = - 857.0 +/- 2.8 kJ mol-1; DELTA(f)H(m)empty set[Ni(Phala)2, cr] = - 898.6 +/- 3.0 kJ mol-1. A linear correlation between the standard molar enthalpies of formation of the crystalline nickel(II) amino acid complexes and the crystalline amino acids is established. Estimations of the standard molar enthalpies of sublimation of the nickel(II) amino acid complexes are presented. The total binding energies in nickel(II) complexes of amino acids and of beta-diketonate ligands are compared.

Abstract The Knudsen mass-loss effusion technique was used to measure the vapour pressure as a function of temperature for four crystalline β-diketones. From the temperature dependence of the vapour pressure, the standard molar enthalpies of sublimation δg crH°m(Tm) at the mean temperature Tm of the experimental temperature range were derived, and the standard molar enthalpies of sublimation, at temperature 298.15 K, were calculated: {A figure is presented}.

Abstract A procedure for the estimation of the number and values of acidity constants from variations observed in aqueous Fourier transform infrared spectra of compounds containing carboxylic groups, including fulvic acids, with increasing pH, by using principal component analysis and evolving factor analysis, has been studied. The validation of the procedure was made by treating simulated data without and with random noise and data obtained in experiments with simple carboxylic compounds (acetic, shikimic, maleic, malonic and succinic acids) and binary mixtures of these compounds. The results for fulvic acids show two different types of carboxylic groups with pKa values of 2.8 and 4.6. © 1992.