Prediction of Standard Enthalpies of Formation Based on Hydrocarbon Molecular Descriptors and Active Subspace Methodology

Abstract

Standard enthalpy of formation is an important fuel thermochemical property for energy balance calculation and equilibrium dynamics determination in combustion reactions. In this study, an approach combining the quantitative structure–property relation and the active subspace method was applied to predict the standard enthalpies of formation of different hydrocarbon classes, including alkanes, cycloalkanes, alkenes, alkynes, and aromatics. The standard enthalpies of formation in a database of 1020 hydrocarbons were predicted by a one-dimensional active subspace model, with 902 molecule topological indices being used as input descriptors. The correlation coefficient between the measured and predicted values was 0.99, and the average absolute error was 6.74 kJ/mol. The sensitivity of the prediction output to each descriptor was further evaluated, which enables us to build simplified models by only considering the most representative descriptors. Also, to assess the influences of model simplification on the prediction performance, the relation between the descriptor number and the prediction accuracy was explored. It was observed that simplified but well-predictive models can be established when the top 10 influential descriptors were selected for model building, and the correlation coefficient between the predicted and measured standard enthalpies of formation was as high as 0.96.