Question

What green principles are satisfied by the replacement of traditional hydrogenation using H2 with transfer hydrogenation using ammonium formate? What principles are negatively impacted by switching from H2 to NH4O2CH?

Answer 1

In comparison with catalytic reduction using molecular hydrogen, transfer reduction using hydrogen donors has advantages based on green principle. Molecular hydrogen is a gas and hence easily ignited and presents considerable hazards, particularly on the large scale. In the case of hydrogen donors, there is no usage of gas and no pressure vessels are needed. It requires only simple stirring of solutions. It also provides enhanced selectivity in reduction.

Negative impact upon usage of hydrogen donors: Possible variations with hydrogenation using a catalyst and molecular hydrogen ; change of catalyst, solvent and temperature are possible in hydrogenation. But in hydrogen donors, a new dimension opened up because the choice of hydrogen donor can affect the reaction through its competitive adsorption onto the catalyst surface. Thus, rate and specificity of reduction are amenable to control through choice of hydrogen donors.