Stereochemistry of Dichlorocarbene Addition to Alkenes: A Collaborative, Discovery-Based Experiment for the Organic Chemistry Laboratory

摘要

A multifaceted experiment, accessible to students either in an introductory organic chemistry course or in a more advanced laboratory setting, is described for investigating the addition of dichlorocarbene to E- and Z-beta-methylstyrenes. The innovative exercise, which integrates elements of synthesis, mechanisms, instrumental analysis, computational chemistry, and collaboration, provides students with an opportunity to learn important laboratory skills while highlighting key concepts covered in class. In particular, the coupling constants from H-1 NMR spectroscopy are used to diagnose the stereochemistry of addition, and integral ratios are evaluated to determine percent conversion of the starting alkenes into dichlorocyclopropanes. The experimental observations are correlated with results from calculations of the singlet-triplet energy gap in the carbene.