The effect of crown ethers on the reactivity of alkoxides. Part 2. The reaction of potassium isopropoxide and 2,4-dinitrohalogenobenzenes in propan-2-ol-benzene

Abstract

The reaction between potassium isopropoxide and 1-chloro-(3) or 1-iodo-(4) 2,4-dinitrobenzene has been studied in propan-2-ol-benzene (1 : 1) with and without added crown ethers dicyclohexano-18-crown-6 (1), and 18-crown-6 (2). Substantial amounts of 2,4-dinitrophenol are formed upon addition of the crown ethers together with the expected 1-isopropoxy-2,4-dinitrobenzene derived from normal nucleophilic substitution. The kinetic order in base in the presence of the potassium complexing agents is less than unity. The radical anion of 1-chloro-2,4-dinitrobenzene has been identified in the system containing (1). These results are explained in terms of the intervention of a nucleophilic-radical reaction pathway of the S_RN1 type leading to the phenol.