Novel Improvement of the Van Der Waals Forces Characterization from Published Vaporization Enthalpies

Abstract

It has been proposed in 2020 to characterize the intermolecular Van der Waals and hydrogen bonding forces of volatile organic compounds (VOCs) by means of four molecular descriptors (or parameters) established from known and easily obtained molecular properties. These properties are: refractive index at 25°C, intrinsic molecular volume, molecular polar surface area, normal boiling point, number of hydroxyl radicals and number of pentavalent nitrogens. The sum of the four molecular parameters thus defined was found to equal the normal boiling enthalpy with a high correlation coefficient (r = 0.95) for a first dataset of 445 VOCs, and confirmed in a second one of 180 compounds including liquids, solids and gases. The normal boiling enthalpy values for these two datasets being between 20 and 55 kJ/mol, the first purpose of the present study has been to test the validity of the proposed 2020 model for a total of 616 compounds whose boiling enthalpy range is between 20 and 75 kJ/mol. Since the 2020 model was inaccurate for normal boiling enthalpy values above 55kJ/mol, the second objective of this study has been to overcome this
limitation.