Thermochemistry of Hydrocarbons. Back to Extended Hückel Theory
1Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain, and Institute of Computational Chemistry, Universitat de Girona, 17071 Girona, Spain.
Abstract:
A modified Extended Hückel method that provides accurate values of heats of formation and structural parameters of hydrocarbons is described. The results are reported for an extensive set of molecules and radicals belonging to different classes. The calculated heats of formation for 120 molecules and 26 radicals are close to the experimental data with the mean absolute error of 1.90 kcal/mol. The internal consistency of the calculated data allows reliable prediction of the reaction enthalpy for various hydrocarbon transformations. The proposed scheme is computationally very efficient, and the calculation of a large system requires only a few seconds on a PC. A computer program for the calculation is provided in the Supporting Information .
Related Concept Videos
Hess's Law
Enthalpy and Heat of Reaction
Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control
Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Reduction of Alkenes: Catalytic Hydrogenation
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...


