Accurate Quantum-Chemical Prediction of Hydrogenation Enthalpies of Some
Unsaturated Organic Compounds in the Gas Phase
Abstract
The standard enthalpies of hydrogenation of 29 unsaturated hydrocarbon
compounds were calculated in the gaseous state by the CCSD(T) theory of
level with the 6-31g(d) and cc-pVXZ, where X =D, T, as well as by
complete basis set limit extrapolation using two different formulas.
Geometries of compounds were optimized at the M06-2X/6-31g(d) level.
This M06-2X geometries were used in the CCSD(T) and extrapolation
calculations with cc-pVXZ basis sets. Comparison of calculation and
experimental results shows that the median absolute deviations (MAD)
between the calculated and experimental enthalpies of hydrogenation
range from 8.8 to 4.1 kJ mol-1 at CCSD(T) calculations , and for
calculations, where using complete basis set limit extrapolation, the
MAD have decreased to 1.5 kJ mol-1. The results of some calculations
showed that the deviations from experimental values are located inside
the “chemical accuracy” (±1 kcal mol-1 ≈ ±4.2 kJ mol-1 ). Very good
linear correlations between experimental and calculated enthalpies of
hydrogenation have been obtained at CCSD(T)/TZ method