Selective Oxidation of Saturated Hydrocarbons by the Gif and Gif-Orsay Systems

Abstract

The Gif system1,2 for the selective oxidation of saturated hydrocarbons consists of pyridine (as solvent), acetic acid (or other carboxylic acid), zinc powder (as source of electrons), oxygen and an iron salt as catalyst. The iron salt is rapidly complexed with ortho-dlpyrldyl (produced by reduction of pyridine). This system is interesting because it oxidizes hydrocarbons selectively at the secondary positions giving mainly ketones. Primary and tertiary positions give minor amounts of products. This substitution pattern excludes a radical attack (as in the Fenton reagent). However, adamantane shows exceptional behavior in that tertiary oxidation products arise, at least in part, from carbon radical. This radical partitions itself between oxygen and pyridine. Reduction of oxygen pressure increases the apparent selectivity of the reaction and leads to increased formation of tertiary pyridine coupled products. No such behavior is seen at the secondary position which is, therefore, oxidized without involving carbon radicals.