HOST-GUEST INTERACTION OF PESTICIDE BIFENOX WITH CYCLODEXTRIN MOLECULES. AN ELECTROCHEMICAL STUDY

The reduction of nitroaromatic compound bifenox (methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate) was studied in aprotic solvents in the absence or presence of cyclodextrin (CD) molecules of different cavity sizes. beta CD and gamma CD form complexes with bifenox in DMSO with the complex formation constants (5 +/- 2) x 10(2) M(-1) [beta CD-bifenox] and (3 +/- 1) x 10(2) M(-1) [gamma CD -bifenox], respectively. Bifenox yields a relatively stable anion radical in dimethyl sulfoxide, which is further reduced at more negative potentials by an overall addition of three electrons and four protons to the corresponding phenylhydroxylamine. In the presence of beta CD the first reduction wave of bifenox becomes irreversible, it is shifted towards more positive potentials and the uptake of more than one electron is observed (up to four electrons during the exhaustive electrolysis). The first reduction wave of bifenox is not affected by the addition of glucose confirming that a simple availability of protons from the OH groups is not the main factor in further transformation of anion radical in the presence of beta CD. The complex formation with beta CD facilitates the protonation and additionally protects the molecule from disintegration into 2,4-dichlorophenol. A yield of 2,4-dichlorophenol decreases in the order beta CD, gamma CD and alpha CD, respectively.