VAPORIZATION ENTHALPIES AT 298.15 K OF THE N-ALKANES FROM C-21 TO C-28 AND C-30

The vaporization enthalpies of the n-alkanes reported previously in th e literature are corrected to 298.15 K and compared to vaporization en thalpies obtained from correlation-gas chromatography. The vaporizatio n enthalpies at 298.15 K for C-21-C-28 and C-30 are critically evaluat ed, and the accuracy of measurements derived from some recent torsion effusion measurements is questioned. A series of vaporization enthalpi es consistent with the gas chromatographic results are obtained which correlate with the number of carbon atoms in the molecule. The followi ng vaporization enthalpies in kJ . mol(-1) at 298.15 K are recommended : heneicosane, 107.3 +/- 2.5; docosane, 113.7 +/- 0.3; tricosane, 118. 5 +/- 0.4; tetracosane, 125.6 +/- 2.7; pentacosane, 126.9 +/- 1.4; hex acosane, 139.1 +/- 7.7; heptacosane, 145.6 +/- 8; octacosane, 151.4 +/ - 8.4; triacontane, 162.1 +/- 8.0.