Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part III

Abstract

Group contribution (GC) methods to predict thermochemical properties are eminently important to process design. We report on a GC parametrization for the heat of formation of organic molecules exhibiting chemical accuracy, i.e., a maximum 1 kcal/mol (4.2 kJ/mol) difference between experimental and model values, whilst having a minimum number of parameters to avoid overfitting. We report an extension of recent findings to chloro-alkanes, fluoro-hydrocarbons, benzylhalides, nitro-alkanes, and acetals. Compared to the existing literature, we obtained a superior model exhibiting chemical accuracy, with exceptions when the inherent GC assumption on linearity and additivity is not valid. Moreover, to have a reliable method and not only a low absolute average deviation as reported in most publications, we accepted no or exceptionally few outliers. The example of the 1,3-dioxolane acetals revealed that by adopting the appropriate size of a group representing the acetal leads to a model showing good accuracy. The overall conclusion of the three papers on this topic is that it is feasible to achieve chemical accuracy when using high-quality experimental data and the judicious definition of chemical groups. Despite the GC method being old, the present work shows substantial and necessary increase in performance can still be achieved.

Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy”

“…and understood based on physico-chemical information. We have illustrated this with various examples [5][6][7][8].…”

“…We started an attempt to revise the GC approach for ∆H f and, in the meantime, we succeeded in achieving this goal [5][6][7][8]. Compared to previous approaches, this positive outcome was the result of a number of specific actions.…”

“…Rather than looking at individual data, more parameters are introduced to obtain better agreement with the experimental data, which easily leads to overfitting and incorrect predictions for molecules that were not involved in establishing the group contribution parameter values. Our procedure, as we learned through our recent investigations [5][6][7][8], resulted in an absolute minimum number of GC parameters, thereby avoiding overfitting, as additional parameters are only added based on concrete information on deviations between the model and experimental data and understood based on physico-chemical information. We have illustrated this with various examples [5][6][7][8].…”

“…Our procedure, as we learned through our recent investigations [5][6][7][8], resulted in an absolute minimum number of GC parameters, thereby avoiding overfitting, as additional parameters are only added based on concrete information on deviations between the model and experimental data and understood based on physico-chemical information. We have illustrated this with various examples [5][6][7][8].…”

Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part V

“…Due to the lack of experimental data (the space of organic molecules comprises many billions of different molecules), predictive models are highly desired. This work is the continuation of work that resulted in four earlier papers [1][2][3][4]. The aim is to have a method available which allows accurate predictions to be obtained for the heat of formation of organic molecules, i.e., with chemical accuracy.…”