Enthalpies of combustion, vaporization, and formation of some alkanenitriles, and the CH 2-increment in the alkanenitrile series

Abstract

Energies of combustion and enthalpies of vaporization at 298.15 K were measured for some alkanenitriles and enthalpies of formation were derived for the compounds in the liquid and gaseous states. The results are: Δ H° f(1) kJ mol −1 Δ H° v kJ mol −1 Δ H° f kJ mol −1 Octanenitrile −107.4 ± 1.5 56.80 ± 0.27 −50.6 ± 1.5 Decanenitrile −158.4 ± 1.8 66.84 ± 0.37 −91.6 ± 1.8 Undecanenitrile −184.5 ± 2.0 71.14 ± 0.14 −113.4 ± 2.0 Dodecanenitrile - 76.12 ± 0.14 - Tetradecanenitrile −260.1 ± 2.6 85.29 ± 0.51 −174.8 ± 2.7 The uncertainties given represent twice the final overall standard deviations of the means. Least-squares analysis of the enthalpies of formation from the literature (1–3) and from the present study gives: ΔH° f{ H(CHCN,g} kJ mol −1 = (95.20 ± 1.33) − (20.815 ± 0.203)m, (m ⩾ 3), where the uncertainties represent twice the calculated standard deviations. The CH 2-increment is in good agreement with the generally accepted value. (4) The enthalpies of vaporization at 298.15 K of alkanenitriles can be represented by: Δ H° v{H(CH 2 ) m CN} kJ mol −1 = 23.50 + 4.736m where V m is the molar volume. The mean and maximum deviations between calculated and experimental values are 0.19 and 0.41 kJ mol −1, respectively