Enthalpies and entropies of sublimation of some primary alkylamides

The vapor pressures of some primary alkylamides, as later on reported, were measured by a torsion-effusion method in rather extended intervals of temp erature. The following pressure-temperature equations were selected: propan amide, log(p/kPa) = (10.6 +/- 0.4) - (3940 +/- 200) K/T, Delta T = (283-343 ) K; butanamide, log(p/kPa) = (11.1 +/- 0.4) - (4290 +/- 200) K/T, Delta T = (298-347) K; hexanamide, log(p/kPa) = (11.0 +/- 0.4) - (4430 +/- 200) K/T , Delta T = (301-371) K; octadecanamide, log(p/kPa) = (16.2 +/- 0.4) - (737 0 +/- 200) K/T, Delta T = (384-459) K; 2-methylpropanamide, log(p/kPa) = (1 1.2 +/- 0.3) - (4300 +/- 200) k/T, Delta T = (288-354) K; 2,2-dimethylpropa namide, log(p/kPa) = (12.2 +/- 0.3) - (4640 +/- 100) K/T, Delta T = (298-35 9) K. From these equations the second-law enthalpies and entropies of subli mation were derived. Because the average value of all of the experimental t emperature ranges were sufficiently near room temperature, the obtained the rmodynamic data were assumed as standard. The vaporization of octadecanamid e was studied above the molten compound so that the vaporization data was o pportunely corrected for the fusion data: propanamide, Delta(sub)H degrees( 298 K) = (75 +/- 4) kJ mol(-1), Delta(sub)S degrees(298 K) = (164 +/- 8) J mol(-1) K-1; butanamide, Delta(sub)H degrees(298 K) = (82 +/- 4) kJ mol(-1) , Delta(sub)S degrees(298 K) = (174 +/- 8) J mol(-1) K-1; hexanamide, Delta (sub)H degrees(298 K) = (85 +/- 4) kJ mol(-1), Delta(sub)S degrees(298 K) = (172 +/- 8) J mol(-1) K-1; octadecanamide, Delta(sub)H degrees(298 K) = (1 96 +/- 4) kJ mol(-1), Delta(sub)S degrees(298 K) = (418 +/- 8) J mol(-1) K- 1; 2-methylpropanamide, Delta(sub)H degrees(298 K) = (82 +/- 4) kJ mol(-1), Delta(sub)S degrees(298 K) = (179 +/- 6) J mol(-1) K-1; 2,2-dimethylpropan amide, Delta(sub)H degrees(298 K) = (89 +/- 2) kJ mol(-1), Delta(sub)S degr ees(298 K) = (195 +/- 6) J mol(-1) K-1. Comparisons with the literature dat a are reported.