97732-44-0Relevant articles and documents
Oxidation of Substituted Hydrazines by Superoxide Ion: The Initiation Step for the Autoxidation of 1,2-Diphenylhydrazine
Calderwood, Thomas S.,Johlman, Carolyn L.,Roberts, Julian L. Jr.,Wilkins, Charles L.,Sawyer, Donald T.
, p. 4683 - 4687 (1984)
Superoxide ion (O2-.) in aprotic media and in the gas phase reacts with 1,2-disubstituted hydrazines to produce the anion radical of the 1,2-disubstituted azo compound.The latter species, upon exposure to molecular oxygen, is rapidly and cleanly oxidized to the pure azo compound.This combination of reactions represents a superoxide-catalyzed autoxidation; for 10 mM 1,2-diphenylhydrazine and O2 at 1 atm in dimethyl sulfoxide catalytic turnover numbers in excess of 200 are observed.The reaction cycle parallels the xanthine oxidase catalyzed autoxidation of reduced flavin/xanthine, which produces H2O2 and fractional quantities of O2-..Monosubstituted hydrazines (e.g., PhNHNH2) are oxidized by O2-. with a one-to-two stoichiometry; PhNHNH2 + 2O2-. -> PhH + N2 + 2H2O2-.Mechanisms are proposed for the O2-./hydrazine oxidation processes and for the O2-. induced autoxidation of 1,2-disubstituted hydrazines.
Electron Transfer Reactions. II. The Application of the Marcus Theory in Kinetic Studies of Electron Transfer from Aromatic Hydrocarbon Anion Radicals to Halogen-Substituted Azobenzene Anion Radicals in N,N-Dimethylformamide
Ingemann, Steen,Larsen, Kim V.,Haugshoej, Kenneth B.,Hammerich, Ole
, p. 981 - 989 (2007/10/02)
The kinetics of electron transfer from anion radicals of aromatic hydrocarbons (A) to anion radicals of azobenzene or halogen-substituted azobenzenes (X-AZ; X = H, F, Cl, Br) have been studied in N,N-dimethylformamide by derivative linear sweep voltammetry. .The dianions of the azobenzenes were rapidly protonated by residual water except for 4-bromoazobenzene and 4,4'-dibromoazobenzene where loss of bromide ion was the predominant reaction.The measured values of the rate constant, ki, varied from 3.8x104 M-1 s-1 (A = benzopyrene and X-AZ = azobenzene) to 2.9x107 M-1 s-1 (A = 9-phenylanthracene and X-AZ = 3-chloroazobenzene).The linear regression line, defined by the experimental data plotted as -RTlnki against the free energy difference, -Fo'(X-AZ-./X-AZ2-) - Eo'(A/A-.)> ca. ΔGo, where the formal potentials, Eo', refer to strictly non-aqueous conditions, has a slope of 0.68.This is close to the value, 0.66, predicted by the Marcus theory considering the range and magnitude of the free energy differences.The rate constants, ki, increased upon addition of water (0.1 M) to the solutions, which was accompanied by a decrease of the slope of -RTlnki against -Fo'(X-AZ-./X-AZ2-) - Eo'(A/A-.)> from 0.68 to 0.60.It is suggested that this effect is due to the participation of the hydrogen-bonded species, X-AZ-./H2O and X-AZ2-/H2O, in reactions (i) and (ii), which results in a shift of ΔGo towards lower values.
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 (2007/10/02)
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.
