An Investigation of Intermolecular Forces via Computational Chemistry

By Madison Minvielle, Maria Schneider

Faculty Mentor: Leanna Giancarlo


Dipole moments can be investigated through several different methods including determining the polarity and electronegativity of a molecule and analyzing electrostatic maps. Computational chemistry is a useful tool that can calculate the value of a dipole moment without the need for a laboratory experiment. Semi-empirical basis sets incorporate experimental data to find the dipole moment, whereas ab initio basis sets do not rely on predetermined numerical values. In determining which of two basis sets, PM6, a semi-empirical method, and 3-21G, an ab initio method, provide more accurate data, the dipole moments of ethanol, glucose, phenolphthalein, phenylisothiocyanate, and glyphosate were calculated using computational techniques and the results were compared to literature values. The PM6 dipole values were 2.15 Debye for ethanol, 2.32 Debye for glucose, 5.81 Debye for benzaurin, and undetermined for phenylisothiocyanate and glyphosate. The 3-21G dipole values were 2.07 Debye for ethanol, 2.59 Debye for glucose, 5.66 Debye for benzaurin, 4.48 Debye for phenylisothiocyanate, and 4.00 for glyphosate. The percent errors for the semi-empirical method were -21.44% for ethanol, 38.9% for glucose, and 15.2% for benzaurin compared to literature values. The percent errors for the ab initio method were -22.5% for ethanol, 31.8% for glucose, 17.4% for benzaurin, -57.2% for phenylisothiocyanate, and 24.5% for glyphosate compared to literature values. These data indicate that the ab initio basis set was more accurate.


Leave a Reply

Your email address will not be published. Required fields are marked *