Phase-boundary-potential-driven azo coupling has been demonstrated for the reaction between
hydrophilic arenediazonium ions and lipophilic coupling components in 1,2-dichloroethane (DCE)|water (W)
two-phase systems. Instead of using phase-transfer catalysts, hydrophilic arenediazonium ions are driven into
the DCE phase by externally controlling the potential drop across the polarized DCE|W interface. The diffusion-controlled transfer of arenediazonium ions across the interface is followed by azo-coupling reactions with
coupling components in the DCE phase. The rate of the azo coupling in DCE has been accurately determined
by using potential-step chronoamperometry for the transfer for four arenediazonium ions having different
lipophilicity in the presence of one of four aromatic coupling components in DCE. No appreciable contribution
of the adsorbed reactants to the overall azo-coupling process is detected. An electrochemical approach using
liquid|liquid two-phase systems is advantageous in determining the rate of two-phase chemical reactions and
is promising for elucidating the mechanism of phase-transfer catalysis.
The rate of the interfacial nucleophilic reaction of 1-p-toluenesulfonyl-2,4-dinitronaphthalene (TSDNN) with OH -ions at the polarized nitrobenzene (NB)-water (W) interface was studied using a polarographic technique. The TSDNN partitioned into the aqueous phase underwent a displacement of the p-toluenesulfonyl moiety with OH -. The transfer of one of the products, 2,4-dinitronaphthalate (DNN -), from the W phase to the NB phase was monitored as the current across the interface. The rate constant of the reaction of TSDNN with OH -in the aqueous phase was estimated to be 1.03±0.23 dm 3 mol -1 s -1 at 25˚C, which is ten-times higher than the rate constant of the displacement of 2,4-dinitrofluorobenzene with OH -in the aqueous phase, 1.01±0.13×10 -1 dm 3 mol -1 s -1 . The contribution from the reactions in the NB phase and at the interface to the formation of DNN -seems to be negligible, suggesting the absence of an interfacial facilitation of the reaction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.