Enthalpies and heat capacities of transfer of NaBPh4 from water to aqueous urea and the effects on the water structure

The densities and volumetric specific heats of binary mixtures of dimethylsulfoxide (DMSO), acetone (ACT), and acetamide (ACM) in water were measured at 25 °C with a flow densimeter and a flow microcalorimeter. The same properties were also determined for ternary mixtures of 0.1 m LiCl, NaCl, Me4NBr, and Bu4NBr in ACT–water and DMSO–water mixtures, and volumes for 0.1 m Bu4NBr in ACM–water and urea–water mixtures. The derived apparent molal volumes and heat capacities of nonelectrolytes in water and the transfer functions of the electrolytes from water to the mixed solvents suggest that, contrary to urea, the present non-electrolytes are slightly hydrophobic but, with the possible exception of ACT, their overall influence on water structure has practically no influence on the various solute–solute interactions.

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Thermodynamics of bolaform electrolytes. V. Enthalpies and heat capacities in aqueous urea solutions

Journal of Solution Chemistry ◽

10.1007/bf00654337 ◽

1976 ◽

Vol 5 (3) ◽

pp. 203-211 ◽

Cited By ~ 2

Author(s):

R. E. Verrall ◽

L. W. Dickson

Keyword(s):

Heat Capacities ◽

Bolaform Electrolytes ◽

Aqueous Urea

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Thermodynamic properties of tetraalkylammonium halides: volumes, heat capacities, and expansibilities in H2O, D2O and urea–water mixtures from 278 to 328 K

Canadian Journal of Chemistry ◽

10.1139/v76-309 ◽

1976 ◽

Vol 54 (14) ◽

pp. 2163-2183 ◽

Cited By ~ 76

Author(s):

Gérald Perron ◽

Nicole Desrosiers ◽

Jacques E. Desnoyers

Keyword(s):

Transfer Functions ◽

Heat Capacities ◽

Excess Functions ◽

Free Energies ◽

Aqueous Urea ◽

Hydrophobic Bond ◽

Hydrophobic Solutes ◽

Molal Volumes ◽

The Difference ◽

Tetraalkylammonium Halides

The densities and heat capacities per unit volume of the symmetrical tetraalkylammonium bromides (R4NBr) were measured in H2O, D2O, and 3 m aqueous urea from 0.01 to 1 mol kg−1 and from 5 to 55 °C with a flow digital densimeter and a flow microcalorimeter. Expansibilities were also measured at 25 °C for the same electrolytes in H2O and urea–water mixtures with a dilatometer. Apparent molal volumes [Formula: see text] heat capacities [Formula: see text] and expansibilities [Formula: see text] were derived. The [Formula: see text] of R4NCl and R4NI were also measured in H2O at 25 °C. The effect of urea concentration was investigated at 25 °C in the case of Bu4NBr.Once allowance is made for the anion, the properties of the larger R4N+ behave essentially as hydrophobic nonelectrolytes in water. The transfer functions from H2O to D2O have the same sign as the hydration functions and the transfer functions from H2O to urea–water mixtures the opposite sign. Whatever is the origin of the interactions giving rise to the peculiar behavior of hydrophobic R4N+ in water, these interactions are larger in D2O and smaller in the presence of urea.The excess volumes, heat capacities, and expansibilities of Bu4NBr and Pen4NBr, once corrected for the long-range Debye–Hückel interactions, all have the same sign as the hydration functions at infinite dilution, in contrast with excess free energies and enthalpies. This suggests some kind of cooperative effect as two hydrophobic solutes interact with each other without the formation of a hydrophobic bond. No conclusions can be drawn from the difference in excess functions in the various aqueous solvents.

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Volumes and Heat Capacities of Transfer of Tetraalkylammonium Bromides from Water to Aqueous Urea Solutions at 25 °C

Canadian Journal of Chemistry ◽

10.1139/v73-029 ◽

1973 ◽

Vol 51 (2) ◽

pp. 187-191 ◽

Cited By ~ 22

Author(s):

P. R. Philip ◽

J. E. Desnoyers ◽

A. Hade

Keyword(s):

Transfer Functions ◽

Pure Water ◽

Heat Capacities ◽

Tetraalkylammonium Bromides ◽

Apparent Molal Volumes ◽

Aqueous Urea ◽

Molal Volumes

The apparent molal volumes and heat capacities of tetraalkylammonium bromides were measured in urea–water mixtures at 25 °C. The volumes and heat capacities of transfer from water to urea-water mixtures indicate that structural hydration effects are smaller in urea–water mixtures than in water. Also a comparison with the corresponding transfer functions from H2O to D2O suggests that urea–water mixtures are less structured than pure water.

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