Theoretical Approach on W-Shaped Excess Heat Capacities of Some Linear and cyclic OxaalKane-AlKane Systems

The excess heat capacities, CpE, throughout the entire concentration range have been determined at 30 °c, 40 °cand 50 °c of linear and cyclic oxaalkane systems : 2,5,8,11,14-pentaoxapentadecane (tetraglyme) with dodecaneand 1,4 dioxane with dodecane .For all these mixtures CpE has a w shaped concentration dependence (two minimum speared by amaximum). By decreasing the molecular size of their component, the second minimum towards highconcentration disappear at 30 °c and 40 °c but persist at 25 °c.CpE behaviour correlates with degrees of non-randomness in the mixtures as quantified by theconcentration-concentration correlation function Scc witch is calculated using quasichemical Guggenheim-Barker-Kehiaian theory with a group-interaction model and assuming interaction between molecular surfaces[2].The selected linear and cyclic oxaalkane-Alkane systems studied; accordingly, the influence oftemperature, the size and molecular structure on the excess heat capacities has been analysed.