Greening the organic chemistry laboratory: a comparison of microwave-assisted and classical nucleophilic aromatic substitution reactions

An experiment is described for the undergraduate organic chemistry lab which compares microwave-induced organic reaction enhancement (MORE) to that of more traditional synthetic procedures. MORE and traditional reflux procedures for substituting thiocyanate, ethylamine and diethylamine nucleophiles for bromide in nucleophilic aromatic substitution reactions on 1-bromo-2,4-dinitrobenzene are given. Recrystallization affords products of sufficient purity for characterization by C-13 NMR, mass spectrometry and melting point. As students compare the two synthetic methods, MORE procedures are consistently observed to be quicker, easier, greener and result in higher yields. Student instructions, instructor notes and example NMR and mass spectra obtained by students are provided in Supplemental material.