Modeling S_N2 and E2 Reaction Pathways and Other Computational Exercises in the Undergraduate Organic Chemistry Laboratory

Computational chemistry techniques have become increasingly important tools for chemists seeking to address scientific questions. As such, it is important that undergraduate chemistry students develop competence in this emerging field of chemistry. One strategy to gain proficiency involves exposing students to computational methods of increasing depth and complexity during each year of their laboratory curriculum, rather than solely at late stages of their education. The computational chemistry exercises described herein are designed to be completed in one introductory-level organic chemistry laboratory period, and they build upon concepts covered in traditional organic lecture and lab curricula. Students generate electrostatic potential maps for substituted acetic acids to analyze bond polarity and pK_a, model acetate to explore resonance, and conduct conformation searches for monosubstituted cyclohexanes to examine the influence of sterics on conformational preference. They also generate reaction coordinate diagrams for substitution and elimination reactions between 2-bromobutane and various alkoxide bases. Students are asked to examine the energetics of starting materials, possible products, and theoretical transition states. All aspects of the exercises align with traditional topics, and thus reinforce their significance.