Molecular Modeling and Nuclear Overhauser Enhancement Spectroscopy (NOESY): Tools for Studying the Regioselective Bromination of 3-Bromoanisole

The use of molecular modeling for predicting chemical reactivity has been highly successful in the industrial and academic research communities. For this reason, increased emphasis has been placed on molecular modeling in the undergraduate curriculum. In the described experiment, the bromination of 3-bromoanisole, students are encouraged to use molecular modeling software as a tool for predicting chemical reactivity. Besides introducing students to molecular modeling, this experiment incorporates the use of nontraditional, less hazardous reagents and solvents for electrophilic aromatic bromination reactions. Lastly, nuclear Overhauser enhancement spectroscopy (NOESY) is introduced as a tool for structural elucidation. Although there are a number of aspects to this experiment, two 3-hour laboratory periods are sufficient because the results from semiempirical (AMI) geometry optimizations, which are complete in seconds, were almost identical to the higher order, more time-intensive ab initio (3-21G*) calculations. In addition, the experimental time was greatly shortened by the discovery that catalytic HCl(aq) reduces the reaction time from 5 hours to 18 minutes.