Revised Group Additivity Values for Enthalpies of Formation (at 298 K) of Carbon–Hydrogen and Carbon–Hydrogen–Oxygen Compounds

Abstract

A program has been undertaken for the evaluation and revision of group additivity values (GAVs) necessary for predicting, by means of Benson’s group additivity method, thermochemical properties of organic molecules. This review reports on the portion of that program dealing with GAVs for enthalpies of formation at 298.15 K (hereinafter abbreviated as 298 K) for carbon–hydrogen and carbon–hydrogen–oxygen compounds. A complete database of experimental data for gas, liquid, and crystal (solid) phase enthalpies of formation is presented. The GAVs, ring strain corrections, and non-nearest neighbor interactions derived from the database are presented in tabular form, together with a description of their evaluation and comments on reliability, uncertainties, and missing or questionable data.

Detailed Kinetic Study of the Ring Opening of Cycloalkanes by CBS-QB3 Calculations

“…RSE obtained at a CBS-QB3 level from direct electronic energies and those obtained from isodesmic reactions are in a very good agreement with values proposed by Cohen [56] and based on group additivity method. For a linear alkane, the bond dissociation energy (BDE) can be assimilated with the activation enthalpy since the recombination of the two free radicals is barrierless.…”

Fischer-Tropsch Synthesis: Development of a Microkinetic Model for Metal Catalysis

“…The standard enthalpy of a surface reaction is defined as: (18) where the enthalpy of the analogous surface reaction in gasphase is: (19) The same type of equations holds for the calculation of standard entropies of surface reactions. Enthalpies and entropies of the analogous surface species in gas-phase are calculated with an in-house algorithm based on Benson's group additivity values for alkanes, alkenes and radical species [18,[22][23][24]. Gas-phase empirical data for the molecules involved in the chain initiation reactions (equations (1) to (8)) are taken from tabulated values [25].…”

Calculation of Molecular Thermochemical Data and Their Availability in Databases

“…In addition, ring strain and nonbonded interactions are also taken into account, such as the repulsive 1,4 or gauche interaction of two methyl groups, and the cis and ortho interactions. Attempts were made to evaluate other noncovalent interactions, for example hydrogen-bonding interactions between two OH groups in vicinal diols and related compounds (Cohen 1996). However, not many went into common practice, partly due to the lack of accurate experimental data, and partly because of the intrinsic non-additivity of the contributions of such extended It is important that care should be paid to the proper consideration of symmetry numbers when entropy contributions are calculated.…”