Enthalpies and Entropies of Sublimation of Some Primary Alkylamides

• Published in: Journal of chemical and engineering data Vol. 45; no. 2; pp. 237 - 241
• Main Authors: Brunetti, Bruno, Gatta, Giuseppe Della, Piacente, Vincenzo
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-03-2000
• Subjects: Chemical thermodynamics; Chemistry; Elements, mineral and organic compounds; Exact sciences and technology; General and physical chemistry; Thermodynamic properties; Secondary amide; Vapor pressure; Heat of sublimation; Enthalpy; Entropy; Primary amide; Experimental study; Thermodynamic properties
• ISSN: 0021-9568; 1520-5134
• DOI: 10.1021/je9902701

The vapor pressures of some primary alkylamides, as later on reported, were measured by a torsion−effusion method in rather extended intervals of temperature. The following pressure−temperature equations were selected:  propanamide, log(p/kPa) = (10.6 ± 0.4) − (3940 ± 200) K/T, ΔT = (283−343) K; butanamide, log(p/kPa) = (11.1 ± 0.4) − (4290 ± 200) K/T, ΔT = (298−347) K; hexanamide, log(p/kPa) = (11.0 ± 0.4) − (4430 ± 200) K/T, ΔT = (301−371) K; octadecanamide, log(p/kPa) = (16.2 ± 0.4) − (7370 ± 200) K/T, ΔT = (384−459) K; 2-methylpropanamide, log(p/kPa) = (11.2 ± 0.3) − (4300 ± 200) K/T, ΔT = (288−354) K; 2,2-dimethylpropanamide, log(p/kPa) = (12.2 ± 0.3) − (4640 ± 100) K/T, ΔT = (298−359) K. From these equations the second-law enthalpies and entropies of sublimation were derived. Because the average value of all of the experimental temperature ranges were sufficiently near room temperature, the obtained thermodynamic data were assumed as standard. The vaporization of octadecanamide was studied above the molten compound so that the vaporization data was opportunely corrected for the fusion data:  propanamide, Δsub H°(298 K) = (75 ± 4) kJ mol-1, Δsub S°(298 K) = (164 ± 8) J mol-1 K-1; butanamide, Δsub H°(298 K) = (82 ± 4) kJ mol-1, Δsub S°(298 K) = (174 ± 8) J mol-1 K-1; hexanamide, Δsub H°(298 K) = (85 ± 4) kJ mol-1, Δsub S°(298 K) = (172 ± 8) J mol-1 K-1; octadecanamide, Δsub H°(298 K) = (196 ± 4) kJ mol-1, Δsub S°(298 K) = (418 ± 8) J mol-1 K-1; 2-methylpropanamide, Δsub H°(298 K) = (82 ± 4) kJ mol-1, Δsub S°(298 K) = (179 ± 6) J mol-1 K-1; 2,2-dimethylpropanamide, Δsub H°(298 K) = (89 ± 2) kJ mol-1, Δsub S°(298 K) = (195 ± 6) J mol-1 K-1. Comparisons with the literature data are reported.