Hydrogenation of Biphenyl Using a Hydrogen Storage Alloy as a Hydrogenation Reagent

Article abstract of DOI:10.1246/bcsj.69.1599

A detailed investigation of the hydrogenation reaction of biphenyl with MmNi_3.5Co_0.7Al_0.8H_4.2 [Mm: mixture of La, Ce, Pr, and Nd (30 : 52 : 5 : 13 wt ratio)] to give either cyclohexylbenzene or bicyclohexyl was performed. Time profiles of the amounts of hydrogen evolved from the alloy and that introduced into biphenyl during the reaction were measured; it was suggested that the hydrogen absorbed by the alloy could predominantly react with the substrate, and the hydrogen released into the gas phase played only a minor role in the reaction. The deuteration of biphenyl with the deuterated alloy, MmNi_3.5Co_0.8Al_0.8D_3.5, was also examined; a GC-MS analysis of the reaction mixture indicated that a H-D exchange between the hydrogen in the substrate and the deuterium in the alloy took place as a parallel reaction to hydrogenation of the aromatic rings, and, as a result, the product cyclohexylbenzene appeared to contain 3-9 deuterium atoms.