Accurate prediction of enthalpies of formation for a large set of organic compounds

Abstract

This article describes a multiparameter calibration model, which improves the accuracy of density functional theory (DFT) for the prediction of standard enthalpies of formation for a large set of organic compounds. The model applies atom based, bond based, electronic, and radical environmental correction terms to calibrate the calculated enthalpies of formation at B3LYP/6-31G(d,p) level by a least-square method. A diverse data set of 771 closed-shell compounds and radicals is used to train the model. The leave-one-out cross validation squared correlation coefficient q(2) of 0.84 and squared correlation coefficient r(2) of 0.86 for the final model are obtained. The mean absolute error in enthalpies of formation for the dataset is reduced from 4.9 kcal/mol before calibration to 2.1 kcal/mol after calibration. Five-fold cross validation is also used to estimate the performance of the calibration model and similar results are obtained.

Understanding Mechanism and Designing Strategies for Sustainable Synthesis of Zeolites: A Personal Story

“…[93] The choice of AlPO-5 was due to its advantages such as excellent hydrothermal and thermal stabilities, large micropores (0.73 nm), and easy substitution of aluminum sites in the tetrahedral framework with a wide range of metal ions. [94] The ordinary organic templates for the synthesis of AlPO-5 are triethylamine (TEA), [95,96] tripropylamine (TPA), [97] piperidine, and dicyclohexylamine, which are toxic. [98] The design of non-toxic templates for the synthesis of AlPO-5 zeolite involved the search for products containing nitrogen atoms with stable molecular structure in animal metabolism, because these compounds are always non-toxic.…”

Empirically Corrected Electronic Structure Calculations Applied to the Enthalpy of Combustion Physical Chemistry Laboratory

“…Here, we present an extension of the traditional bomb calorimeter experiment in which we emphasize the use of electronic structure methods and symbolic mathematical software to gain a deeper understanding of the process of combustion. We recognize that the calculation of an accurate standard enthalpy of formation, and therefore, the standard enthalpy of combustion, Δ c H m ⊖ , for any particular hydrocarbon is quite difficult from an electronic structure perspective − and may therefore be prohibitively expensive in the typical teaching laboratory setting. Additionally, the conceptual complexity of these calculations may not be appropriate for an undergraduate physical chemistry course on chemical thermodynamics .…”