2 research outputs found
Solvent and pH Dependences of Mixing Enthalpies of <i>N</i>‑Glycylglycine with Protocatechuic Acid
Protocatechuic
acid (PA) is a natural phenolic compound which has
been proven to have chemopreventive property against chemically induced
carcinogenesis. The mixing enthalpies of PA with <i>N</i>-glycylglycine in sodium phosphate and potassium phosphate buffer
solutions with different pH values have been investigated by mixing-flow
isothermal microcalorimetry at <i>T</i> = 298.15 K. The
heterotactic enthalpic interaction coefficients (<i>h</i><sub><i>xy</i></sub>) in the pH range of phosphate buffer
solution from 3.0 to 8.0 have been calculated according to the McMillan–Mayer
theory. Trends of the enthalpic pairwise interaction coefficients
(<i>h</i><sub><i>xy</i></sub>) with increasing
pH in both phosphate buffer solutions were obtained. The solvent and
pH dependence of the <i>h</i><sub><i>xy</i></sub> were discussed in terms of molecular interactions between solvated
solute molecules
Thermodynamic Difference between Protocatechualdehyde and <i>p</i>‑Hydroxybenzaldehyde in Aqueous Sodium Chloride Solutions
The
enthalpies of dilution of protocatechualdehyde and <i>p</i>-hydroxybenzaldehyde in the aqueous sodium chloride solutions
were measured by using a mixing-flow microcalorimeter at 298.15 K.
Densities of the ternary homogeneous systems at different temperatures
(293.15, 298.15, 303.15, 308.15, and 313.15 K) were also measured
with a quartz vibrating-tube densimeter. The homogeneous enthalpic
interaction coefficients (<i>h</i><sub>2</sub>, <i>h</i><sub>3</sub>, and <i>h</i><sub>4</sub>) were
calculated according to the excess enthalpy concept based on the calorimetric
data. The apparent molar volumes (<i>V</i><sub>Ï•</sub>) and standard partial molar volumes (<i>V</i><sub>Ï•</sub><sup>0</sup>) of the
investigated system were computed from their density data. The variation
trends in <i>h</i><sub>2</sub> and <i>V</i><sub>Ï•</sub><sup>0</sup> with increasing
salt molality were obtained and discussed in terms of the (solute
+ solute) and (solute + solvent) interactions. The experimental results
showed that the molecular structures of protocatechualdehyde and <i>p</i>-hydroxybenzaldehyde, especially the number of hydroxyl
groups, have evident influence on their thermodynamic properties.
The thermodynamic data obtained in this work may be helpful for exploring
the structure–function relationship of protocatechualdehyde
and <i>p</i>-hydroxybenzaldehyde