Enthalpies and entropies of fusion of ten alkane-α, ω-diamines H2 N– (CH 2)n– NH2 where 3⩽n⩽12

Abstract

Enthalpies ΔfusHmand temperaturesTfus of fusion for a homologous series of ten alkane- α, ω -diamines H2 N– (CH 2)n– NH 2, wheren= (3 to 12), were measured by differential scanning calorimetry. Entropies of fusionΔfusSm were derived from the experimental results. Temperatures of fusion increased as a function of n, and showed a marked odd–even effect with higher values for even terms. The odd–even effect was also observed for molar enthalpies and entropies of fusion as a function of n. Comparison was made with literature values for temperatures, enthalpies, and entropies of fusion of isoelectronic linear alkanes H3 C– (CH 2)n– CH 3. Results were interpreted on the basis of the literature data on crystal structures of the alkane- α, ω -diamines and their corresponding intermolecular interactions. The ΔfusHmandΔfusSm interplay provided distinct linear plots for odd and even terms of alkane- α, ω -diamines showing, a common slope value,Tfus≈ 380 K, which was also found for odd and even linear alkanes withn= (6 to 18).