Isotope effects in aqueous systems. 12. Thermodynamics of urea-h4/water and urea-d4/water-d2 solutions

Volumetric properties of binary mixtures of N, N- dimethylformamide with water or water- d2 at temperatures from 277.13 K to 318.15 K

“…(4) Thermodynamic properties of binary mixtures of H 2 O with various dipolar aprotic solvents have been extensively reported by many workers, whereas studies on the properties of corresponding systems containing D 2 O instead of H 2 O are scarce. (5)(6)(7)(8)(9)(10)(11)(12)(13) We have recently initiated in our laboratory a systematic investigation of deuterium isotope effects on thermodynamic properties in binary mixtures of water with various dipolar aprotic solvents. This is an extension of our previous research on deuterium isotope effects (14)(15)(16)(17)(18)(19)(20) and the presently ongoing study on aqueous dipolar aprotic solvents as highly basic media.…”

Are isotopic mixtures ideal?

“…The value of the ∆p E /p ratio gives one some feeling about the magnitude of the deviation of isotopic mixtures from ideal behavior. For example, the experimental ∆p E of 3.2 Pa at 25°C for the equimolar mixture of C 6 H 6 and C 6 D 6 (for comparison, the vapor pressure difference between C 6 H 6 and C 6 D 6 is 360 Pa) [7] corresponds to a nonideality of about 0.02-0.03 %. The excess vapor pressure corresponds to a value of G E = 0.58 J/mol, which is two to three orders of magnitude smaller than the excess Gibbs energies typically observed in binary mixtures of nonisotopic simple molecules (see Table 1).…”

“…From the experimental excess vapor pressure for the equimolar C 6 H 6 /C 6 D 6 mixture at room temperature (3.2 Pa), the value for µ E∞ (2.3 J/mol) has been calculated from the equation µ E∞ = 4G E equimolar [7]. The PBB approach using the difference in molar volumes (the molar volume of benzene is larger by 0.27 % than that of deuterated benzene [22]) and the isothermal compressibility of liquid benzene gives a value of 0.33 J/mol for µ E∞ [14,16].…”

“…In a recent edition of the last textbook [6], it is demonstrated on the example of the mixture of C 6 H 6 and C 6 D 6 [7] that even the mixtures of isotopic species exhibit very slight departures from ideal behavior.…”

Thermodynamic Analysis of Isotope Effects on Triple Points and/or Melting Temperatures

“…VPIE data for liquid [26] and solid [14,27] isoto pomers of C6H6/C6D6 and C6H 12/C6D 12 are avail able, and this permits calculation of TPIEs for these molecules. The results are in Table 2.…”