(189ac) Importance of Molecular Conformations on Dipole Moment and Thermophysical Properties Estimation

The knowledge of thermophysical properties, such as vapor viscosity and thermal conductivity, for a wide range of molecules is crucial for industrial applications. However, such properties are often not available for many species of interest, especially for proprietary compounds. Experimental measurement is expensive and time-consuming. Thermophysical property estimation methods are available that depend in part on the value of the gas phase dipole moment, which is difficult to measure experimentally. Alternatively, it has been shown that quantum chemical methods such as density functional theory (DFT) can be used to accurately estimate the dipole moment vector for simple molecules. However, dipole moments for molecules having a large number of conformational degrees of freedom have been very challenging to calculate. This is because the conformation of the molecule can greatly affect its dipole moment. In this work, we present an efficient computational formalism for estimating the gas phase dipole moment of molecules with many conformational degrees of freedom. We compare thermophysical properties estimated from dipole moments determined from experiments and from computations to establish the reliability of our approach.