Learning Green Chemistry Principles by Comparing Three Synthetic Routes to a Copper-NHC (NHC = N-heterocyclic carbene) Complex

The implementation of a laboratory exercise in an undergraduate chemistry course, where students perform a comparison of three different synthetic methods toward [Cu(Cl)(IPr)]-complexes (IPr = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), is described. The students are introduced to the continuous improvement of reactions in terms of green chemistry and are provided a taste of mechanochemistry as a synthetic methodology. The direct comparison of three methods leading to the copper complexes provides an opportunity to teach green chemistry metrics including atom economy, environmental factor, mass intensity, reaction mass efficiency, and optimum efficiency, as well as Green Star; and challenges them to question the use of solvents in chemical syntheses.