A solventless carbonyl addition reaction as a guided inquiry laboratory activity for second-year undergraduate organic students

A less hazardous, environmentally friendly, and energy-efficient Knoevenagel reaction performed using proline as a catalyst has been designed and implemented within a sophomore-level organic chemistry laboratory as a guided inquiry activity. The main learning objective is to enable students to identify and understand various green chemistry principles such as atom economy, use of safer chemicals, design for energy efficiency, and inherently safer chemistry for accident prevention. Students were successful in synthesizing α,β-unsaturated diesters using unknown substituted benzaldehydes (later identified by the students spectroscopically) and Meldrum’s acid at room temperature in the presence of proline as a catalyst without the need for an additional base. By analyzing 1H NMR spectroscopic data, infrared spectroscopy, and mass spectrometry to identify the synthesized product, the unknown benzaldehyde starting material, and the major reaction pathway, students have enhanced their spectroscopy skills and developed a deeper understanding of the mechanism of the reaction that may not be covered in the lecture course.