1 research outputs found
Enthalpies of Dilution of Penicillamines in <i>N</i>,<i>N</i>‑Dimethylformamide + Water Mixtures at 298.15 K
Dilution enthalpies of two penicillamine enantiomers,
namely, d-penicillamine, l-penicillamine, and their
racemate d,l-penicillamine, in <i>N</i>,<i>N</i>-dimethylformamide
(DMF) + water mixtures of various compositions have been determined
at 298.15 K respectively, using an isothermal titration calorimeter
(MicroCal ITC200). According to the McMillan–Mayer theory,
homochiral enthalpic pairwise interaction coefficients (<i>h</i><sub>XX</sub>) of the three penicillamines in DMF + water mixtures
of different mass fractions (<i>w</i><sub>DMF</sub> = 0
to 0.3) have been calculated regressively. It is found that <i>h</i><sub>XX</sub> coefficients of each enantiomer and their
racemate change increasingly with <i>w</i><sub>DMF</sub> to the maxima at <i>w</i><sub>DMF</sub> = 0.20 and then
decrease relatively rapidly, which follows the order <i>h</i><sub>LL</sub> > <i>h</i><sub>DD</sub> ≈ <i>h</i><sub>RR</sub> > 0 (R represents the racemate mixture
of
penicillamine). The results are discussed from the point of view of
competitive equilibrium between hydrophobic and hydrophilic interactions
in solutions