Abstract
The thermodynamic properties of a substance are key to predicting its behavior in physical and chemical systems. Specifically, the enthalpy of formation and entropy of a substance can be used to predict whether reactions involving that substance will proceed spontaneously under conditions of constant temperature and pressure, and if they do, what the heat and work yield of those reactions would be. Prediction of enthalpy and entropy of substances is therefore of value for substances for which those parameters have not been experimentally measured. We developed a database of 2869 experimental values of enthalpy of formation and 1403 values for entropy for substances composed of stable small molecules, derived from the literature. We developed a model for predicting enthalpy of formation and entropy from semiempirical quantum mechanical calculations of energy and atom counts, and applied the model to a comprehensive database of 16,417 small molecules. The database of small-molecule thermodynamic properties will be useful for predicting the outcome of any process that might involve the generation or destruction of volatile products, such as atmospheric chemistry, volcanism, or waste pyrolysis. Additionally, the collected experimental thermodynamic values will be of value to others developing models to predict enthalpy and entropy.
Highlights
Summary We present a dataset for the prediction of thermodynamic parameters for compounds and its application to a set of 16,411 small molecules [1]
The dataset contains a compilation of measured enthalpy of formation for 2869 compounds, measured entropy for 1403 compounds, and temperature dependence of parameters for 172 compounds
These can be used as a reference source in their own right, or used to build a model for predicting these values for new compounds. We describe building such a model and applying it to 16,411 small molecules in the ‘All Small Molecules’ collection [1]
Summary
Note that what is listed in this dataset is absolute entropy S, not entropy of formation ∆S. Entropy of formation can readily be derived from absolute entropy from Equation (3). As was the case for the enthalpy data, only molecules with conventional bonding, and not radicals or isolated ions, were included, and sources with multiple entries are represented by multiple columns. A subset of data was taken from Yaws. Entropy data on 1403 compounds were collected. Predicted values for entropy calculated by the QM semiempirical method, in kCal/mol
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