Thermodynamic quantities for the acid dissociation of alkylammonium ions in water over a wide temperature range

Chlorophyll a Behavior in Aqueous Solvents: Formation of Nanoscale Self-Assembled Complexes

“…The hydrophobic effect and the high value of the dielectric constant can consequently account for Chl a aggregation, to minimize the interaction of the hydrophobic part of the molecule with water. The presence of hydrophobic interactions in the water rich region of acetone−water mixtures and the evidence that on the contrary, MeOH forms hydrogen bonds with water, thus participating to the water structure, can likewise explain the respective presence and absence of the Chl a polymer in these solvents. ,, Notwithstanding a strong hydrophobic effect, which has been reported in the literature for a water mole fraction 0.8, , similar considerations cannot be invoked to clarify the behavior of Chl a in DMF, in which the polymer was never detected. The dielectric constant and dipole moment of DMF do not differ remarkably from those of ACN (see Table ).…”

Apparent molar volumes of aqueous solutions of some organic solutes at the pressure 28 MPa and temperatures to 598 K

“…The ionization constants at T=298.15 K and p=0.1 MPa used for these calculations were taken from Robinson and Stokes, (48) Larson and Hepler, (49) and Jones and Arnett. (50) For the electrolytes, corrections to infinite dilution were made using A v values at p=28 MPa, calculated from data tabulated by Pitzer et al (14) Since the molality dependencies of V f for nonelectrolytes are not known at higher temperatures and are probably small in any case, the values reported are assumed to be V (49) Jones and Arnett, (50) and Bergstro¨m and Olofsson, (55) and D r C a p,m for ionization of water was calculated from the high-temperature, high-pressure D r C a p,m for NaCl, NaOH, and HCl tabulated by Pitzer et al, (14) Simonson et al, (56) and Sharygin, (51) respectively, and the molar heat capacity of water was from Hill. (11) Quadratic equations were fitted to the resulting D r C a p,m for the reactions of interest at the various temperatures and substituted into equation (14) for evaluation of the corresponding equilibrium constants at p = 28 MPa at T = (373.15, 448.15, and 523.15) K. These were then used with the corresponding DV m s of ionization through iterative processes in a manner similar to the calculations at T = 298.15 K to obtain V f at m=0.12 mol·kg −1 corrected for hydrolysis or ionization.…”

Copolymers sensitive to temperature and pH in water and in water+oil mixtures: A DSC, ITC and volumetric study

“…(5) and (6)) explains the less positive enthalpy for the second dissociation process highlighting the importance of the hydration effects on the energetics of the copolymer dissociation. As concerns entropy, it has been observed [31] that negative entropy changes for the dissociation of various alkylammonium ions are consistent with the hydrophobic interactions between water and parts of the alkyl groups close to the nitrogen atom, which become relevant when the positive charge is lost as a consequence of dissociation. In our case, the positive and the negative value for the two equilibria can be therefore explained to the light of the first dissociation still leading to charged specie and to the second one generating uncharged specie.…”