Clay-Kinnear-Perren condensation

What is Clay-Kinnear-Perren condensation?

The Clay-Kinnear-Perren condensation, also known as the Kinnear-Perren-Clay reaction or simply the Kinnear-Perren reaction, involves the synthesis of alkylphosphonic dichlorides from alkyl chlorides, phosphorous trichloride, and aluminum chloride. Clay first reported this reaction in 1951, and it was later extended by Kinnear and Perren in 1952. The resulting alkylphosphonic dichlorides can be further converted into alkylphosphonic acids or other phosphorus-containing derivatives.

Clay-Kinnear-Perren condensation
Clay-Kinnear-Perren condensation

The success of this reaction depends on several factors, including the order in which the reagents are mixed, the control of the reaction temperature, anhydrous conditions of the reagents and apparatus, and the final molar ratio of water to ionic complex in hydrolysis. If AlCl3 is dissolved in alkyl chloride before the addition of PCl3, no reaction occurs, and the molar ratio of H2O to complex being hydrolyzed must be between 7:1 and 11:1. The complex formed from alkyl chloride, PCl3, and AlCl3 has high thermal stability and an ionic structure, as indicated by its conductivity in nitromethane. The reaction yields rearranged products when using propyl or higher primary or secondary alkyl chlorides, similar to the Friedel-Crafts alkylation. However, no rearrangement occurs with the complex from chloromethyltrimethylsilane, even though this compound undergoes a Wagner-Meerwein rearrangement to chlorodimethylethylsilane when treated with AlCl3. Chlorosilane does not undergo this reaction either. Thus, the utility of this reaction is limited by the tendency of rearrangement and the specific molar ratio requirements.

The reaction presents a convenient approach to synthesizing alkyl phosphonic chloride, a crucial intermediate in the production of alkyl phosphonic acid and its corresponding esters.

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