Studies of Organic Catalytic Reactions. V. The Function of the Chelates formed in the Hydrolysis of 2-Cyanopyridine with Metal Oxide Catalysts

Abstract

Abstract When 2-cyanopyridine is refluxed with water in the presence of nickel or copper oxide, it is easily hydrolyzed and affords a chelate compound of the acid with nickel or copper. On the other hand, 3- or 4-cyanopyridine affords only the corresponding free amide by the same reaction. The interfering effect of thiophene is not observed in the reaction of 2-cyanopyridine, but it is observed in the case of the 3- or 4-cyanopyridine. When 2-cyanopyridine is refluxed with an aqueous solution of nickel or cupric chloride, it is hydrated to form a chelate of the amide with nickel or copper. These chelates are hydrolyzed with the metal oxides in water to afford the chelates of the acid. Pyridine-2-carboxylic acid amide is also hydrolyzed to the chelate of the acid, but the hydrolysis of the 3- or 4-amide isomer does not occur under the same conditions. The four chelates of the acid and amide are excellent catalysts for the hydration of 2-cyanopyridine, giving the free amide in a high yield. From these facts, it may be presumed that: 1) The adsorption of 2-cyanopyridine or its amide on the catalysts is stereospecific and results in the formation of a kind of chelate. Upon forming the acid, the metal atom of the catalyst is drawn out of the catalyst to form the chelate. 2) The metal oxide is the most suitable catalyst for the chelate-type adsorption and for the chelate formation. 3) The chelate of the acid formed during the hydrolysis of 2-cyanopyridine acts as another catalyst in the formation of the free amide, then, the amide is further converted into the chelate of the acid by means of the metal oxide catalyst.