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.

Substituent effects on electroreduction of the carbon-halogen bond

1981 ◽  
Vol 34 (11) ◽  
pp. 2331 ◽  
Author(s):  
RS Abeywickrema ◽  
EW Della
Keyword(s):  
Reduction Potential ◽  
Halogen Bond ◽  
Substituent Effects ◽  
High Yield ◽  
Polarographic Reduction ◽  
Electric Field Effects ◽  
Controlled Potential Electrolysis ◽  
Half Wave ◽  
Controlled Potential ◽  
Substituted 1

Polarographic reduction of a series of 4-substituted 1-iodobicyclo[2,2,2]octanes has been examined in an attempt to assess the effect of substituents on the half-wave reduction potential. It is found that the values of E� do not show a linear correlation with the relevant σ1 constants; the deviations are discussed in terms of the relative importance of the steric and electric field effects of the substituent. Controlled-potential electrolysis of a number of the substrates reveals that the hydrocarbon corresponding to fission of the carbon-iodine bond is formed in high yield.

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 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.

The polarography of beryllium halides in acetonitrile

1967 ◽  
Vol 20 (2) ◽  
pp. 211 ◽  
Author(s):  
PJ Shirvington ◽  
TM Florence ◽  
AJ Harle
Keyword(s):  
Dissociation Constants ◽  
Experimental Results ◽  
Acid Dissociation ◽  
Polarographic Reduction ◽  
Insufficient Evidence ◽  
Acid Dissociation Constants ◽  
Beryllium Chloride ◽  
Halogen Acid

Polarographic reduction steps for various beryllium salts in acetonitrile have been recorded in tetrapropylammonium perchlorate, chloride, bromide, and iodide supporting electrolytes. The experimental results indicate that free halogen acid (which is strongly associated in acetonitrile) is produced as a result of solvolysis of beryllium. The concentration of water affects the degree of solvolysis by altering the halogen acid dissociation constants. A water to beryllium ratio of 4 : 1 brings about almost complete (99%) solvolysis of 3mM beryllium chloride. However, insufficient evidence was obtained to prove conclusively that water was the solvolytic agent.

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