91158-75-7Relevant academic research and scientific papers
Electrogenerated Bases: The Role of Weak Electroinactive Proton Donors and the Effect of Electrocatalysis on the Redox Behavior of Azobenzene
Cheng, Spencer,Hawley, M. Dale
, p. 3388 - 3392 (1985)
The stepwise electrochemical reduction of PhN=NPh in DMF-0.1 M (CH3)4NPF6 can give, depending upon proton availability, three anionic products.The basicities of these electrogenerated bases increase in the order PhN=NPh- radical -Ph -N-Ph.Water (pKaMe2SO=31.6), which is capable only of protonating PhN-N-Ph, causes the reversible PhN=NPh- radical/PhN-N-Ph redox couple to shift to more positive potential.From the magnitude of the potential shift and the reported value of pKaDMF(H2O) = 34.7, pKaDMF(PhNHN-Ph) is estimated to be 38.1 Ph2C=NNH2 and PhNHNHPh both protonate PhN-N-Ph irreversibly.The PhNHN-Ph that is produced in this reaction is subsequently consumed in an electrocatalytic cycle which involves PhN=NPh as the oxidant, the less easily oxidized PhNHN-Ph as the reductant, and proton transfer from PhNHNPh to the conjugate base of the added proton donor as the rapid, irreversible follow-up reaction.The anodic peak for the irreversible oxidation of PhNHN-Ph is discernible only at scan rates in excess of about 1 V/s at -51 deg C.Protonation of PhNHN-Ph by both diethyl malonate (pKaMe2SO=16.4) and fluorene (pKaMe2SO=22.6) and of PhN=NPh- radical by diethyl malonate is irreversible and affords PhNHNHPh and the conjugate base of the added proton donor as the principal electroactive products.
