Reduction potentials of thiuram disulfide/dithiocarbamate couples in acetone/water

1982 ◽  
Vol 35 (12) ◽  
pp. 2455 ◽  
Author(s):  
PJ Nichols ◽  
MW Grant
Keyword(s):  
Dissociation Constants ◽  
Saturated Calomel Electrode ◽  
Substituent Effects ◽  
Acid Dissociation ◽  
Reduction Potentials ◽  
Half Wave ◽  
Acetone Water ◽  
Potentiometric Measurements ◽  
Dithiocarbamic Acid ◽  
Reducing Properties

Reduction potentials relative to the saturated calomel electrode, E�, of a series of thiuram disulfide/ dithiocarbamate couples have been measured in 30% v/v water in acetone and at ,μ 0.2 moll-1 (NaNO3) by a combination of potentiometric measurements and equilibrium constant determinations for thiolate/disulfide interchange reactions. E� values lie in the range -250 to -340 mV which place dithiocarbamates as intermediate between thiophenolate (E� - 540 mV) and ethylxanthate (E� -206 mV) in reducing properties. The significant effect on EO of varying the substituents on the nitrogen in the dithiocarbamates correlates with the substituent effects on the acid dissociation constants of the parent dithiocarbamic acid and with trends in the half-wave potentials for metal-based oxidation and reduction of transition metal dithiocarbamate complexes.

Substituent effects on polarographic reduction of some photographic color intermediates

1976 ◽  
Vol 54 (8) ◽  
pp. 1205-1210 ◽  
Author(s):  
Ahmad S. Shawali ◽  
Bahgat E. El-Anadouli
Keyword(s):  
Dissociation Constants ◽  
Substituent Effects ◽  
Protonated Form ◽  
Acid Dissociation ◽  
Polarographic Reduction ◽  
Substituent Constant ◽  
Acid Dissociation Constants ◽  
Controlled Potential Electrolysis ◽  
Half Wave ◽  
Controlled Potential

Polarographic reduction of two series of benzoylacetanilides has been investigated in 40% (by volume) ethanolic Britton–Robinson buffers. One series (A) contains substituents on the anilide moiety, and the second (B) has substituents on both the anilide and benzoyl moieties. Polarographic controlled-potential electrolysis data indicate that the electroactive species in both series is the protonated form (ArCOCH2CONHAr′)H+. The reduction half-wave potentials of anilides of series A were found to be independent of the nature of the substituent, whereas those of series B show a good linear relationship when plotted vs. the σ substituent constant of the substituent on the benzoyl moiety (ρ = 0.284, r = 0.995). Values of the acid dissociation constants of the keto (K1) and enol (K2) tautomers of the anilides of series A were calculated; unlike their E1/2 values, the pK1 data show a linear correlation with the Hammett substituent constant, σ. The pK2 values show, however, little variation with σ.

Merostabilization in radical ions, triplets, and biradicals. 4. Substituent effects on the half-wave reduction potentials and n,π* triplet energies of aromatic ketones

1980 ◽  
Vol 58 (23) ◽  
pp. 2537-2549 ◽  
Author(s):  
William J. Leigh ◽  
Donald R. Arnold ◽  
Robert W. R. Humphreys ◽  
Po Cheong Wong
Keyword(s):  
Substituent Effects ◽  
Radical Ions ◽  
Normal Behaviour ◽  
Reduction Potentials ◽  
Half Wave ◽  
Substituent Constants ◽  
Parameter Function ◽  
Two Parameter ◽  
Wave Reduction ◽  
Abinitio Calculations

The half-wave reduction potentials, measured by cyclic voltammetry, and n,π* triplet energies, measured by phosphorescence spectroscopy, were determined for a series of eighteen symmetrically and unsymmetrically substituted benzophenones. Attempts are made to correlate the results with Hammett substituent constants. Better correlations are observed when the data are correlated with a two-parameter function consisting of Hammett substituent constants and a set of substituent parameters describing variations in free radical stability. Significant deviations from "normal" behaviour are observed for benzophenones substituted by both electron-donating and electron-withdrawing substituents. These deviations are attributed to merostabilization of the radical-like species, and an empirical approach designed to evaluate the importance of this effect is developed. Abinitio calculations of molecular orbital energies in meta- and para-substituted benzaldehydes are used to evaluate the substituent effects on E1/2red and ETn,π* in terms of the effect on the energies of the n- and π*-orbitals.

Substituenteneffekte und Störung von π-Systemen, XXXV Radikalanionen Zinn-substituierter Naphthaline/ Substituent Effects and Perturbation of n Systems, XXXV Radical Anions of Tin-Substituted Naphthalenes

1978 ◽  
Vol 33 (11) ◽  
pp. 1223-1226 ◽  
Author(s):  
Hans Bock ◽  
Wolfgang Kaim ◽  
Holger Tesmann
Keyword(s):  
Charge Transfer ◽  
Substituent Effects ◽  
Esr Spectra ◽  
Group Iv ◽  
Ionization Potentials ◽  
Radical Anions ◽  
Spin Distribution ◽  
Reduction Potentials ◽  
Half Wave ◽  
Wave Reduction

Abstract Novel radical anions of trimethylstannyl substituted naphthalenes and their ESR spectra are reported. Both 119 Sn and 117 Sn coupling can be assigned unequivocally. The perturbation of π systems by R3X substituents of group IV b elements X = C, Si, Ge, Sn and Pb is discussed with respect to photoelectron ionization potentials, charge transfer excitations, half-wave reduction potentials and ESR spin distribution.

Substituent effects on acid dissociation constants of N,N-substituted dithiocarbamic acids

1973 ◽  
Vol 45 (2) ◽  
pp. 363-367 ◽  
Author(s):  
Vernon L. Frampton ◽  
William J. Evans ◽  
James C. Kuck
Keyword(s):  
Dissociation Constants ◽  
Substituent Effects ◽  
Acid Dissociation ◽  
Acid Dissociation Constants

Preparation and nuclear magnetic resonance studies of diaryloxytriphenylphosphoranes. Correlation of substituent effects with 31P N.M.R. chemical shifts

1984 ◽  
Vol 37 (12) ◽  
pp. 2447 ◽  
Author(s):  
Mv Itzstein ◽  
ID Jenkins
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Dissociation Constants ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Acid Dissociation ◽  
Linear Free Energy Relationship ◽  
Acid Dissociation Constants ◽  
Magnetic Resonance Studies ◽  
Linear Free Energy ◽  
Electron Donating Groups

Triphenylphosphine and diisopropyl azodicarboxylate react with phenols in tetrahydrofuran or chloroform at 0° to give diaryloxytriphenylphosphoranes. A linear free-energy relationship has been found between the 31P n.m.r. chemical shifts of many of these phosphoranes and the acid dissociation constants of the corresponding phenols. In general, electron-withdrawing groups on the phenol result in downfield 31P n.m.r. chemical shifts, while electron donating groups result in up-field shifts.

Spectroscopic and electrochemical properties of intramolecularly hydrogen-bonded compounds. Ortho-hydroxyazobenzenes

1981 ◽  
Vol 59 (5) ◽  
pp. 821-827 ◽  
Author(s):  
Salvatore Millefiori ◽  
Arcangelo Millefiori
Keyword(s):  
Bond Formation ◽  
Substituent Effects ◽  
Lone Pair ◽  
Intramolecular Hydrogen Bonding ◽  
Photoelectron Spectra ◽  
Polarographic Reduction ◽  
Reduction Potentials ◽  
Half Wave ◽  
Experimental Findings ◽  
Intramolecular Hydrogen

The gas-phase uv photoelectron spectra and the half-wave polarographic reduction potentials in acetonitrile solutions of a series of 2-hydroxy-5-methylazobenzene have been determined. The first three IP's and the E1/2 values were linearly correlated with σ+ and σ constants, respectively. E1/2 can also be linearly related to the energy of the lowest unoccupied molecular orbital. Effects of the intramolecular hydrogen bonding on the pe spectra and on the polarographic reduction of the title compounds were evaluated by comparing the experimental findings in 2-hydroxy-5-methylazobenzene, 2-methoxy-5-methylazobenzene, and p-hydroxyazobenzene. On H-bond formation, the antibonding combination of the two nitrogen lone-pairs, n−, and the oxygen lone-pair is ionized at a slightly higher energy and at a lower energy, respectively, than in the non H-bonded compound. The first π-ionization band is slightly lowered in energy in the non H-bonded structure, probably owing to a normal substituent effect. These features are not maintained in the 4'-nitro derivative, where the band encompassing the n− ionization remains at the same potential in both structures, while the first π band in the non H-bonded compound moves toward higher IP. Spectral differences between the bonded and nonbonded structures are the result of a balance of substituent effects, and of both hydrogen bond and orbital interactions. The solution electron affinity of the studied compounds increases on H-bond formation by an amount comparable with the experimental strength of the H-bonding. INDO/S-CI calculations are in qualitative agreement with the experimental results.

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