Polymer Supported Reagent – Chromic Acid on Anion Exchange Resin and Kinetics of Oxidation of Alcohol to Ketone
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Polymer supported oxidizing agents are very useful in organic synthesis, due to easy recovery and regeneration. The selective formation of 4- fluoro acetophenone from 4-fluorophenyl ethanol by using chromic acid supported on anion exchange resin Amberlyst A-26 (Cl) with divinylbenzene containing a quaternary functional group has been investigated in detail. It was found to be through ester formation. In a slow step the ester decomposes and produces Cr(IV). Then Cr(IV)oxidizes with another molecule of 4- fluorophenyl ethanol to generate a free radical in a fast step. The free radical reacts with another polymeric reagent to form Cr (V). Finally Cr (V) reacts with 4- flouorophenyl ethanol to produce 4-fluoro acetophenone. We have obtained interesting results in the oxidation of alcohol to carbonyl compound by using a HCrO4– resin. The various activation parameters have been calculated and suitable mechanism is proposed.
KEYWORDS:Kinetics; oxidation; polymer support; chromic acid
