Heat Capacities, and Enthalpies of Fusion of a Series of Eleven Primary Alkylamides by Differential Scanning Calorimetry

Molar heat capacities at constant pressure, Cp,m, of 11 primary alkylamides (butanamide, 2-methylpropanamide,pentanamide, 2,2-dimethylpropanamide, hexanamide, octanamide, decanamide, dodecanamide,hexadecanamide, octadecanamide, docosanamide) determined by differential scanning calorimetry (DSC)increased as a function of temperature and were fitted into linear equations. Values at 298.15 K obtained byinterpolating/extrapolating the smoothed equations displayed a linear increase with the number of carbonatoms. The Cp,m contribution of the CH2 group was (22.5 ( 0.7) J ·K-1 · mol-1, in agreement with ourprevious results for linear alkane-R,ω-diamides and alkane-R,ω-diols as well as with the literature data forvarious series of linear alkyl compounds. Temperatures, enthalpies, and entropies of the solid-solid transitionsand fusion of alkylamides were also determined. They are discussed with reference to the packing patternsdescribed in the literature.