Pressure Hydrogenation of Phenols over Rhodium Catalysts

Low-Pressure Hydrogenation of Phenols over Rhodium Catalysts 

A solution of resorcinol (11 g) in sodium hydroxide solution (4.8 g of sodium hydroxide in 20 ml of water) is hydrogenated in the presence of 1.1 g of 5 % rhodium on alumina for 16-18 hours at 50 psi initial pressure in a Parr apparatus. The reduction stops after the absorption of 1 equivalent of hydrogen. The catalyst is removed by filtration through celite, and the aqueous solution is carefully acidified with concentrated hydrochloric acid at 0°. The crude product is collected by filtration, dried in air, and recrystallized from benzene to give 1,3-cyclohexanedione, mp 105-107.  

A solution of hydroquinone (11.0 g) in 50 ml of acetic acid containing 1.1 g of 5 % rhodium on alumina is hydrogenated at 50 psi in a Parr apparatus. Three equivalents of hydrogen are rapidly absorbed. The catalyst is removed by filtration through celite. 

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II. Low-Pressure Hydrogenation of Phenols over Rhodium Catalysts... 

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