Collect. Czech. Chem. Commun. 2004, 69, 2134-2146

Protic Acidity of Some Aliphatic and Alicyclic Hydrocarbons in the Gas Phase and in Solution. An Empirical and Computational Link

Esther Quintanillaa, Juan Z. Dávalosa, Rebeca Herreroa, Pilar Jiméneza, Ibon Alkortab and José-Luis M. Abbouda,*

a Instituto de Química Física Rocasolano, CSIC. C/Serrano, 119. E-28006 Madrid, Spain
b Instituto de Química Médica, CSIC. C/Juan de la Cierva, 3. E-28006 Madrid, Spain


Here we report the results of the study of a set of thirteen hydrocarbons R-H not leading to extensively charge-delocalized anions R- upon ionization, R-H → R- + H+. It essentially involves the following: (i) The computation at the G2 level of the changes in thermodynamic state functions for this process in the gas phase. The reliability of the computational method was further assessed by comparison with CCSD(T)/Aug-cc-pVTZ results. (ii) A direct comparison of the experimentally available thermodynamic (gas phase) and kinetic (solution) data pertaining to this reaction. (iii) A careful re-examination of the experimental data sets and the Brønsted-type relationships derived therefrom by using the computed thermodynamic data. This treatment suggests the existence of mechanistic features affecting the experimental data and indicates the need for further experimental and computational work.

Keywords: Carbanions; Thermodynamics; Gas-phase reactivity; Charge-delocalized anions; Alicyclic hydrocarbons; Protic acidity; Ab initio calculations; CCSD(T).

References: 42 live references.