Efficient Ab Initio Estimation of Formation Enthalpies for Organic Compounds: Extension to Sulfur and Critical Evaluation of Experimental Data

Abstract

The efficient protocol for the estimation of gas-phase enthalpies of formation developed previously for C, H, O, N, and F elements was extended to sulfur. The protocol is based on a local coupled cluster with single, double, and perturbative triple excitation [CCSD(T)] approximation and allows rapid evaluation of compounds with sizes computationally prohibitive to canonical CCSD(T) using quadruple zeta basis sets. As a part of model development, a comprehensive review and critical evaluation of experimental data were performed for 87 sulfurcontaining organic and inorganic compounds. A compact model with only three empirical parameters for sulfur introduced to address the effects beyond frozen core CCSD(T) was developed. The model exhibits approximately 2 kJ•mol −1 standard deviation over a set of experimental values for a diverse collection of sulfur-containing compounds. The complete basis set version of the model demonstrates a similar performance and requires only one empirical parameter. Multiple problems with the existing experimental data were identified and discussed. In addition, a lack of reliable data for certain important classes of sulfur compounds was found to impede the model generalization and confident performance assessment.

Reconciliation of Experimental and Computed Thermodynamic Properties for Methyl-Substituted 3-Ring Aromatics. Part 1: 9-Methylanthracene

“…To further refine this estimate of the torsion barrier, singlepoint LCCSD(T) energy calculations with aug-cc-pVQZ and aug-cc-pV5Z basis sets were performed, followed by a twopoint extrapolation to a complete basis set (CBS). 77 The best theoretical geometries, computed with DF-MP2/aug-cc-pVQZ, were used. The results are shown in the lower portion of Table 17.…”

Current Practices and Continuing Needs in Thermophysical Properties for the Chemical Industry

“…This absence is often due to a lack of experimental data caused by component instability or insufficient sample purity. Methods based on quantum density functional theory (QDFT) are approaching uncertainties that are close to experimental data in predicting heats of reactions . Gupta et al suggest using QDFT to supplement experimental heats of reaction in order to develop new groups or update some of the existing parameters in the Benson estimation method while ensuring consistent and reliable results for all unit operations .…”

Industrial Expectations of a Pure Component Database for Thermodynamic and Transport Properties

“…We note that the estimation error could be reduced by coupling optimized geometries from DFT with higher level methods such as CCSD(T), as has been performed by Kazakov and Paulechka for many classes of ideal gas molecules. 214,215 Quantum chemistry can also be coupled with the Benson group contribution approach for the estimation of ideal gas thermochemical properties. Quantum chemistry is computationally tractable and accurate for small molecules such as those in Table 8, but performs less well when many possible molecular conformations exist (e.g., for polymers).…”

“…In all cases, we find agreement to within the expected error of 5–7 kcal/mol. We note that the estimation error could be reduced by coupling optimized geometries from DFT with higher level methods such as CCSD­(T), as has been performed by Kazakov and Paulechka for many classes of ideal gas molecules. , …”