Voltammetric Reductions of Ring-Substituted Acetophenones. 3. A Collaborative Sophomore-Level Molecular Modeling Exercise Correlating Experimental and Theoretical Electrochemical and Spectroscopic Data

An experiment suitable for introductory organic chemistry students is described. In it, students perform relatively simple semi-empirical and ab initio calculations on a series of ring-substituted acetophenones. The calculated LUMO energies and bond-stretching frequencies derived from PM3, AM1, Hartree–Fock (3-21G*), and density functional theory (DFT) were compared against reduction potentials (E1/2) acquired using differential pulse voltammetry at a glassy carbon electrode and stretching frequencies for selected bonds using either DRIFT or absorbance FT–IR data. Correlation for the LUMO energies ranged from excellent (3-21G*) to very poor (DFT); for the stretching frequencies, agreement was best using PM3 and worst using DFT, but all correlations could be called fair only.