Green Hydrogenation: Solvent-Free Hydrogenation of Pinenes for An Undergraduate Organic Chemistry Laboratory

Reorienting organic chemistry laboratories with an emphasis on systemic thinking can only be beneficial to students. Addressing the challenges of climate change and the development of renewable resources with a fundamental reaction, such as the hydrogenation of an alkene, will allow students to see organic chemistry as a science beneficial to society. For this purpose, a green organic laboratory experiment in which students performed solvent-free catalytic hydrogenation of beta- or alpha-pinene was developed. Using a homemade high- or low-pressure autoclave, solvent-free hydrogenation of beta- or alpha-pinene over Pd/C produced a mixture of cis- and trans-pinanes. The monitoring of the reaction by NMR, IR, and GC-MS allowed the students to be familiar with the isomerization of an alkene and the shift of an equilibrium according to Le Chatelier's principle. The filtration of the catalyst near the halftime of reaction and the continuation of the hydrogenation off catalyst allowed the students to confirm the heterogeneous nature of the hydrogenation.