The effect of electrochemically generated positive bromine species in acetonitrile on the cleavage of C-Br and C-Cl bonds

The fate of bromine formed from C-Br cleavage during the course of anodic oxidation of alkyl bromides in acetonitrile on platinum has been investigated potentiostatically. It is suggested that positive bromine species are formed and they are potentially reactive towards alkyl bromides, yielding similar products to those obtained by direct anodic oxidation of the same bromides. Furthermore, whereas alkyl chlorides do not undergo C-Cl fission by direct anodic oxidation it is shown that positive bromine species are energetically sufficient to break C-Cl bonds, although not very efficiently. We suggest that a possible structure for the complex between acetonitrile and positive bromine species is mainly [(CH₃CN)₂Br]⁺Br₃^- or [CH₃CNBr]⁺Br₃^- and the mechanism for its formation is discussed. The spectrum of this species found identical to that of Br₃^- (269 nm) in acetonitrile.