William F. O'Hara

Bio: William F. O'Hara is an academic researcher. The author has contributed to research in topics: Ionization & Hydrogen bond. The author has an hindex of 3, co-authored 3 publications receiving 16 citations.

Temperature and power measurements in precision solution calorimetry

Abstract: Presents the design of a calorimetric apparatus, and accompanying circuit schematic, and their application to calorimetry measurements.

pKa values of estrone, 17β-estradiol and 2-methoxyestrone

Abstract: The acid ionization constants of estrone (10.77), 17 beta-estradiol (10.71) and 2-methoxyestrone (10.81) have been determined spectrophotometrically and shown to be consistent with the additivity of substituent effects of the phenol ring. Previously published values for estrone (10.914) and 17 beta-estradiol (10.078) are shown to be incorrect, at variance with the established trend for phenols, and inconcsistent with the similarity of the compounds.

Thermochemistry of solutions of biochemical model compounds 3. Some benzene derivatives in aqueous solution

Abstract: The enthalpies of solution in water have been determined calorimetrically over the temperature range 293.15 to 313.15 K at different concentrations for the following compounds: phenol, benzylalcohol, 2-phenylethanol, 3-phenyl-1-propanol, p -cresol, 2-phenoxyethanol, aniline, 2-phenylethylamine, and 3-phenyl-1-propylamine. From these experiments ΔC p ,2 o values have been calculated. Heat capacities for the pure compounds (298.15 K), including 4-ethylphenol, have also been determined by use of a novel drop calorimeter and these values have been combined with the ΔC p ,2 o values to give the partial molar heat capacities, C p ,2 o , for the compounds at infinite dilution. The thermodynamic results obtained are correlated with results from earlier measurements on aliphatic compounds. The effect of increasing salt concentration on the heat capacity has also been investigated.

Partition coefficients of aromatic organic substances in two-phase mixtures of water and carbon dioxide at pressures from 8 to 30 MPa and at temperatures of 313 to 333 K. Part II

Abstract: In the two phase system of water and supercritical carbon dioxide, the partitioning behavior of two single solutes, aniline and benzaldehyde, was measured at temperatures of 313, 323 and 333 K and pressures up to 30 MPa using a recirculation view cell apparatus. Samples were taken from both phases and analyzed either by UV-spectroscopy or gas chromatography. The partition coefficient in this case is defined as the ratio of molar fractions of a substance in the carbon dioxide-rich phase and the aqueous phase in equilibrium. Partition coefficients between 0.21 and 3.03 were found for aniline and 2.5 up to 62.9 for benzaldehyde. In addition to the single solute measurements, the distribution behavior of an aqueous solution of phenol, benzyl alcohol, cyclohexanol and 2-hexanone was examined at 323 K. While the alcohols were entrained in the fluid phase, the other compounds were retained in the aqueous phase. Analogous to high pressure binary solid fluid phase equilibria, an enhancement factor is introduced to describe partitioning equilibria. Differences in the distribution behavior of single solutes are discussed in terms of the enthalpy of hydration.

Temperature Dependences of Limiting Activity Coefficients and Henry's Law Constants for Nitrobenzene, Aniline, and Cyclohexylamine in Water

Abstract: Recommended data for the limiting activity coefficients ( ) of nitrobenzene, aniline, and cyclohexylamine in water were established as a function of temperature by the simultaneous correlation of the values resulting from specialized vapor−liquid equilibrium measurements and related thermal data for highly dilute solutions. The new values of were determined by the Rayleigh distillation, circulation still, and headspace analysis methods. The limiting partial molar excess heat capacities were derived from measurements by the Picker flow microcalorimetry. These values were combined with all available literature data on the limiting activity coefficients and the limiting partial molar excess enthalpies. This allowed us to produce a thermodynamically consistent fit of between 273 K and 373 K, which was in turn used in combination with pure solute vapor pressures to calculate the Henry's law constants (kH).

The combining ratio of boric acid and alkali borate with mannitol

Abstract: The composition of the complex formed by mannitol and borate was investigated by several methods. Linear relationships found between the H+ and mannitol concentrations (H3BO3 constant) and between pH and log [ H 3 BO 3 ] 1 2 [ mannitol ] for wide ranges of reactant concentrations indicate that H3BO3 and mannitol combine only in a 1:1 ratio and that H3BO3 is present in dilute solutions principally as a dimer. Titration data also suggest a complex having 1 mannitol/B. In aqueous sodium borate the quantities of mannitol required to maintain a prescribed pH as the solution volume is varied give the relationship expected for dimeric borate ion and a 1:1 combining ratio. The heat of complex formation also indicates a 1:1 ratio. The major complexing reaction thus appears to be the splitting of a borate dimer and the formation of 2 moles of a 1:1 complex. A complex with the widely accepted borospirane (di-diol) structure is not present in aqueous solutions.