OXIDATION OF STYRYLPYRIDINIUM DYES BY PERMANGANATE ION

The oxidation of N-alkyl substituted strylpyridinium bromides in both KMnO4 and cetyltrimethylammonium permanganate (CTAP) results in the fo rmation of corresponding substituted benzaldehydes. The oxidation in a queous medium is catalyzed by acid whereas in chloroform medium the re action proceeds at neutral condition, However, the reaction proceeds t hrough the same mechanism in both the media. The faster rate of oxidat ion in aqueous medium by KMnO4 than that in chloroform medium by CTAP has been rationalized through hydrophobic effect. The overall rate equ ation can be represented as rate=k[Substrate](1.5)[Oxidant](-0.75) in aqueous medium and rate=k[Substrate](0.5)[Oxidant](-1) in chloroform m edium. From the substituent effect a transition state with low electro n density at the olefinic carbon has been proposed.