Effects of Quinones on the Protonation Reaction of TCNQ Anion Radical; The Role of a Protonated Quinone as a Strong Electron Acceptor

Various kinds of substituted p-benzoquinones (Q) have been found to accelerate the rate of the reaction between 7,7,8,8-tetracyanoquinodimethane(TCNQ) anion radical and hydrogen chloride in acetonitrile. The stoichiometry of the reaction is altered by the presence of Q from 2TCNQ+2H+=TCNQ+H2TCNQ to 2TCNQ+2H++Q=2TCNQ+QH2. In case of p-benzoquinone, the rate of the disappearance of TCNQ is expressed by v=k[TCNQ] [Q] [H+], where k=3.0×108 M−2 s−1 at 8 °C. From these results, it is concluded that a protonated quinone QH+ is an active species which accepts an electron from TCNQ.