Alkene Hydrogenation via Manganese-Catalyzed Hydrogen Atom Transfer: An Undergraduate Organic Chemistry Experiment

Catalytic hydrogenation of unsaturated bonds, particularly alkenes, is fundamentally important to synthetic chemistry. Conventional alkene hydrogenation methods typically rely on molecular hydrogen (H 2 ) in the presence of noble-metal catalysts, employing either homogeneous or heterogeneous systems. Although these methods are well-established in organic synthesis, their widespread adoption within teaching environments remains limited due to the high cost of noble metals and safety concerns associated with handling H 2 gas. To address these challenges, a cost-effective manganese-catalyzed alkene hydrogenation of citronellyl benzoate via a hydrogen atom transfer (HAT) process was introduced into undergraduate organic chemistry experiments. This method is characterized by mild conditions, high efficiency, and operational simplicity. The experimental procedure includes setting up the reaction under a N 2 atmosphere, monitoring the reaction by thin-layer chromatography (TLC), isolating the product by flash column chromatography, and characterizing the structure by 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. This experiment provides students with practical skills in modern catalytic alkene hydrogenation techniques while enhancing their comprehension of these reactions and the analytical methods. By merging theoretical knowledge with practical laboratory work, this approach not only encourages students to actively participate in organic chemistry experiments but also equips them with the skills needed for future scientific research.