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Issue 1, 1984
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Thermodynamics of solution of homologous series of solutes in water


Values of ΔGs(g → aq) and ΔGs(liq → aq) at 298 K are documented for 14 homologous series of gaseous and liquid solutes, and corresponding enthalpies of solution listed for 7 homologous series. It is shown by a thermodynamic argument that only parameters for the process g → aq can be used to assess solute–water interactions and that the standard state of pure liquid solute includes a different solute–solute interaction term for each solute standard state. For most of the homologous series, parameters for the process g → aq are linear in the number of carbon atoms in the solute; from such linear equations, methylene and group contributions are obtained. It is shown that the methylene increments to ΔGs(g → aq) and to ΔHs(g → aq) are not constant but vary from one homologous series to another. In a few homologous series the methylene increment is not constant, the most outstanding examples being the alkan-1-ols and n-alkanes. Above dodecan-1-ol, ΔGs(g → aq) becomes gradually more negative than expected, so that octadecan-1-ol is 16 times as soluble as calculated from results on the low alkan-1-ols. A similar, but much larger, effect is observed for the n-alkanes: n-octadecane is more soluble than expected by a factor of 5 × 103(the factor for n-hexatriacontane is 2 × 1018) and it is deduced that the n-alkane C51H104 will be as soluble in water as in the non-aqueous solvents ethanol and phenol.

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Article type: Paper
DOI: 10.1039/F19848000153
Citation: J. Chem. Soc., Faraday Trans. 1, 1984,80, 153-181

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    Thermodynamics of solution of homologous series of solutes in water

    M. H. Abraham, J. Chem. Soc., Faraday Trans. 1, 1984, 80, 153
    DOI: 10.1039/F19848000153

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