Rose and Geranium Scents from Lemongrass Oil: A Greener Reduction of Citral

Plant-derived perfumes are excellent examples of biorenewable chemicals and contribute pleasant fragrances to the laboratory. This microscale experiment is a greener adaptation of a conversion of citral (found in lemongrass oil) into nerol (in rose oil) and geraniol (in geranium oil). This updated version minimizes students' exposure to hazardous chemicals by using less solvent and greener solvents. Dichloromethane has been replaced with the greener alternative tert-amyl methyl ether (TAME) for the liquid-liquid extraction, hexane/ethyl acetate has been replaced with either heptane/ethyl acetate or TAME for thin-layer chromatography (TLC), and diethyl ether has been replaced with solventless procedures for gas chromatography-mass spectrometry (GC-MS) and for non-GC MS. Solvent volume has been reduced for the extraction and for MS and NMR analysis. This improved experiment is well suited for undergraduate organic chemistry teaching laboratories and illustrates concepts of biomimetic catalysis, chemoselectivity, spectroscopic characterization, and green chemistry.