1.10.11: Gibbs Energies- Solutions- Solute-Solute Interactions- Pairwise
Analysis of the thermodynamic properties of aqueous solutions was taken a step further by Savage and Wood who envisage two solute molecules A and B in aqueous solution [1]. The total pairwise interaction between these molecules is described in terms of pairwise group-group interaction parameters. Then, for example, the pairwise enthalpic solute-solute interaction parameter \(\mathrm{H}_{\mathrm{AB}\) is written as the sum of products, \(\mathrm{n}_{\mathrm{i}}^{\mathrm{A}} \, \mathrm{n}_{\mathrm{j}}^{\mathrm{B}} \, \mathrm{h}_{\mathrm{ij}}\) where \(\mathrm{n}_{\mathrm{i}}^{\mathrm{A}}\) is the number of A-groups in solute molecule \(\mathrm{i}\) and \(\mathrm{n}_{\mathrm{j}}^{\mathrm{B}}\) is the number of B-groups in solute molecule \(\mathrm{j}\) where \(\mathrm{h}_{\mathrm{ij}}\) is a pairwise enthalpic group interaction parameter. A similar analysis is carried out for interaction Gibbs energies leading to pairwise Gibbs energy parameters \(\mathrm{g}_{\mathrm{ij}}\). So, for example, \(\mathrm{g}(\mathrm{OH}-\mathrm{OH})\) is negative characteristic of a hydrophilic-hydrophilic interaction. Whereas \(\mathrm{g}\left(\mathrm{OH}-\mathrm{CH}_{2}\right)\) is positive indicating 'repulsion' within hydrophobic-hydrophilic pairs. Interestingly \(\mathrm{g}\left(\mathrm{CH}_{2}-\mathrm{CH}_{2}\right)\) is negative" which is indicative of a hydrophobic-hydrophobic attraction (cf. hydrophobic bonding); the corresponding enthalpic pairwise parameter is positive. Thus it is tempting to speculate that hydrophobic attraction is entropy driven [2]; for further comments see references [3-13].
The general approach is readily extended to a consideration of pairwise interactions between added solutes and both initial and transitions states for given chemical reactions in aqueous solution [14-18].
Footnotes
[1] J.J. Savage and R. H. Wood, J. Solution Chem.,1976, 5 ,733.
[2] J.J. Spitzer, S. K. Suri and R. H. Wood, J. Solution Chem.,1985, 14 ,5; and references therein.
[3] S. K. Suri and R. H. Wood, J. Solution Chem.,1986, 15 ,705.
[4] S. K. Suri, J.J.Spitzer, R. H. Wood, E.G.Abel and P.T. Thompson, J. Solution Chem.,1986, 14 ,781.
[5] A. L. Harris, P. T. Thompson and R. H. Wood, J. Solution Chem.,1980, 9 ,305.
[6] For the role of solute stereochemistry see F. Franks and M. D. Pedley, J. Chem. Soc. Faraday Trans. 1, 1983, 79 ,2249.
[7] Amides in N,N-dimethvl formamide: M. Bloemendal and G. Somsen, J. Solution Chem.,1983, 12 ,83.
[8] Solutions in DMF with a modification of the role of the solvent; M. Bloemendal and G. Somsen, J. Solution Chem.,1987, 16 ,367
[9] Interaction between amides and urea in aqueous solution; P. J. Cheek and T. H. Lilley, J. Chem. Soc. Faraday Trans.1, 1988, 84 ,1927.
[10]
- Diols(aq); S. Andini, G. Castronuovo, V. Ella and L. Fasano, J. Chem. Soc. Faraday Trans.. 1990. 86 , 3567.
- Amino acids and peptides; T H. Lilley and R. P. Scott, J. Chem. Soc. Faraday Trans. 1, 1976, 72 ,359.
- Monosaccharides(aq); G. Barone, G. Castronuovo, D. Doucas, V.Elia and G. A. Mattia, J.Phys.Chem.,1983, 87 ,1931.
[11] Urea and polyols(aq); G. Barone, V. Elia and E. Rizzo, J. Solution Chem.,1982, 11 ,687.
[12] Volumes and heat capacities of aromatic solutes(aq); S. Cabani, P. Gianni,V. Mollica and L. Lepori, J. Solution Chem., 1981, 10 ,563.
[13] Small peptides(aq); enthalpies; O. V. Kulikov, A. Zielenkiewicz, W. Zielenkiewicz. V. G. Badelin and A.Krestov , J. Solution Chem., 1993, 22 ,59.
[14] M. J. Blandamer, J. Burgess, I . M. Horn, J. B. F. N. Engberts and P. Warrick Jr., Colloids and Surfaces, 1990, 48 ,139.
[15] M. J. Blandamer, J. Burgess, J. B. F. N. Engberts and W. Blokzijl, Annu. Rep. Prog. Chem., Sect C, Phys. Chem.,1990, 87 ,45.
[16] W. Blokzijl, J. B. F. N. Engberts, J. Jager and M. J. Blandamer, J. Phys. Chem.,1987, 91 ,6022.
[17] M. J. Blandamer, J. Burgess and J. B. F. N. Engberts, Chem. Soc Rev.,1985, 14 ,237.
[18] M. J. Blandamer and J. Burgess, Pure Appl. Chem.,1982, 54 ,2285.