Functional group analysis and machine learning techniques for MIE prediction

Abstract

The successful prediction of minimum ignition energies (MIEs) for 55 flammable organic molecules has been accomplished through group contribution and machine learning methods. The applied techniques include least squares regression, Huber regression, and kernel ridge regression, with the Marrero/Gani method applied to determine structurally dependent descriptors to uniquely characterize each molecule. These descriptors were used as predictors for the aforementioned regressions techniques to develop four predictive models. The rudimentary least squares regression resulted in a modest R2 of 0.939 on the at-large data set, but overpredicted the MIEs of several compounds. An improved least squares regression featured a lower R2 of 0.840, but with virtually no overprediction. Outlier analysis was conducted with the Huber and kernel ridge techniques, and these models exhibited reduced outlier influence and considered the non-linear relationship between predictors and MIEs. These improved algorithms also used L2 regularization to reduce sensitivity of MIE predictions on statistically insignificant descriptors. Resulting R2 values for models developed using the Huber and kernel ridge techniques came out to be 0.878 and 0.991, respectively, when applied to the at-large data set, and featured little overprediction. Thus, it is concluded that simple group contribution methods, optimized by Huber and kernel ridge techniques, are potential modeling alternatives for simple and accurate prediction of organic molecule MIEs.