title: Benchmarking Experimental and Computational Thermochemical Data: A Case Study of the Butane Conformers.
abstract: Due to its crucial importance, numerous studies have been conducted to determine the enthalpy difference between the conformers of butane. However, it is shown here that the most reliable experimental values are biased due to the statistical model utilized during the evaluation of the raw experimental data. In this study, using the appropriate statistical model, both the experimental expectation values and the associated uncertainties are revised. For the 133-196 and 223-297 K temperature ranges, 668 ± 20 and 653 ± 125 cal mol(-1), respectively, are recommended as reference values. Furthermore, to show that present-day quantum chemistry is a favorable alternative to experimental techniques in the determination of enthalpy differences of conformers, a focal-point analysis, based on coupled-cluster electronic structure computations, has been performed that included contributions of up to perturbative quadruple excitations as well as small correction terms beyond the Born-Oppenheimer and nonrelativistic approximations. For the 133-196 and 223-297 K temperature ranges, in exceptional agreement with the corresponding revised experimental data, our computations yielded 668 ± 3 and 650 ± 6 cal mol(-1), respectively. The most reliable enthalpy difference values for 0 and 298.15 K are also provided by the computational approach, 680.9 ± 2.5 and 647.4 ± 7.0 cal mol(-1), respectively.
authors.affiliation: Department of Applied and Environmental Chemistry, University of Szeged , Rerrich B. tér 1, H-6720 Szeged, Hungary.
authors.forename: Dóra
authors.initials: D
authors.lastname: Barna
authors.affiliation: Department of Applied and Environmental Chemistry, University of Szeged , Rerrich B. tér 1, H-6720 Szeged, Hungary.
authors.forename: Balázs
authors.initials: B
authors.lastname: Nagy
authors.affiliation: Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics , P.O. Box 91, H-1521 Budapest, Hungary.
authors.forename: József
authors.initials: J
authors.lastname: Csontos
authors.affiliation: Institute of Chemistry, Laboratory of Molecular Spectroscopy, Loránd Eötvös University , P.O. Box 32, H-1518 Budapest 112, Hungary.
authors.forename: Attila G
authors.initials: AG
authors.lastname: Császár
authors.affiliation: Department of Applied and Environmental Chemistry, University of Szeged , Rerrich B. tér 1, H-6720 Szeged, Hungary.
authors.forename: Gyula
authors.initials: G
authors.lastname: Tasi