Thermodynamic properties of (a butyl ester plus an n-alkane). XIII. H-m(E)and V-m(E) for {xCH(3)(CH2)(u-1)CO2(CH2)(3)CH3+(1-x) CH3(CH2)(2v+1)CH3}, where u=1 to 3 and v=1 to 7

In the framework of a series of studies carried out by our research team, t he excess molar enthalpies H-m(E) and excess molar volumes V-m(E) for 21 bi nary mixtures composed of one of three butyl eaters (ethanoate, propanoate, and butanoate) and one of seven odd n-alkanes (pentane to heptadecane) wer e determined experimentally at T = 298.15 K. Experimentation showed the mix ing processes for these systems to be endothermic, with the H-m(E) values v arying quasi-linearly with n-alkane chain length; there is also a regular v ariation in the V-m(E) values, though the mixtures of the three butyl ester s with pentane presented contraction effects with values of V-m(E) that wer e more negative than expected. The most probable molecular interactions tak ing place in (ester + n-alkane) systems are discussed. Comparison of the ex perimental results with certain theoretical group-contribution models showe d that differences in the estimates increased with increasing molar mass of the mixture components, indicating a need to improve modeling by adapting the models so that they more closely reflect the special circumstances that affect the behaviour of the mixtures in question. (C) 2000 Academic Press.