Thermodynamics of fusion and sublimation for a homologous series of eleven alkane-α,ω-diols HO-(CH2)n-OH: Structure-related odd-even effect

Temperatures and enthalpies of fusion and solid-to-solid transition of a homologous series of linear alkane-alpha, omega-diols, HO-(CH2)(n)-OH where n = (6 to 16), were measured by differential scanning calorimetry (d.s.c.). The enthalpies and temperatures of fusion displayed a marked odd-even effect as a function of the number of methylene groups in the alkyl chains, with even terms showing higher values than odd terms. Thermodynamic parameters of fusion were compared with those of isoelectronic linear alkanes and earlier measured alkane-alpha, omega-diamines, alkane-alpha, omega-diamides and alkane-alpha, omega-dinitriles. Results were discussed with reference to the effects of chain length on crystal structures and packing patterns raised on hydrogen bonding and hydrophobic interaction interplay. The enthalpies of sublimation at T = 298.15 K were obtained from the enthalpies of fusion and the literature enthalpies of vaporisation, both adjusted to 298.15 K. A smoother odd-even pattern was observed for the enthalpies of sublimation. (C) 2013 Elsevier Ltd. All rights reserved.