Substituent effect in addition of cyanide ion to p-substituted 1-benzyl-3-carbamoylpyridinium chlorides

1983 ◽  
Vol 48 (5) ◽  
pp. 1401-1407 ◽  
Author(s):  
Františka Pavlíková-Raclová ◽  
Josef Kuthan
Keyword(s):  
Aqueous Solutions ◽  
Rate Constants ◽  
Substituent Effect ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Cyanide Ion ◽  
Quaternary Salts ◽  
Half Wave ◽  
Substituted 1 ◽  
Mechanism Of The Reaction

The rate constants k2 and equilibrium constants K = k2/k-2 of the title process (A) have been measured in aqueous solutions of eight quaternary salts of nicotinamide I (R = p-XC6H4CH2) at 298 K. The substituent effects of X = CH3O, CH3, H, F, Cl, COOCH3, CN, and NO2 exhibiting the Hammett dependence have been correlated with half-wave potentials of reduction of the depolarizers I, and the correlation results have been discussed with respect to mechanism of the reaction (A).

Kinetic and thermodynamic control of pseudobase formation from C-3 substituted 1-methylquinolinium cations

1984 ◽  
Vol 62 (7) ◽  
pp. 1301-1307 ◽  
Author(s):  
John W. Bunting ◽  
Norman P. Fitzgerald
Keyword(s):  
Aqueous Solutions ◽  
Rate Constants ◽  
Kinetic Data ◽  
Mixing Time ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Stopped Flow ◽  
Thermodynamic Control ◽  
Preferred Species ◽  
Substituted 1

The kinetic and thermodynamic control of pseudobase formation from 3-W-1-methylquinolinium cations has been studied for a variety of substituents (W). Spectral data indicate that, in both aqueous and methanolic solution, the C-2 pseudobases predominate at equilibrium for W = H and Br, while the C-4 pseudobases are the thermodynamically preferred species for W = CONH2, CO2CH3, CN, and NO2. Stopped-flow studies indicate that in all cases the C-2 pseudobases are the kineticallycontrolled products upon basification of the aqueous solutions of these cations. Equilibrium constants (pKR+) have been measured for pseudobase formation at both C-2 and C-4 for each W in all cases where they are experimentally accessible. Substituent effects upon [Formula: see text] correlate with σm for W, while [Formula: see text] depends upon σp−. These substituent effects allow the prediction of [Formula: see text] and [Formula: see text] for the 1-methylquinolinium cation. Rates of C-2 to C-4 pseudobase equilibration have been measured in all cases where the latter species is thermodynamically more stable. These kinetic data allow the evaluation of rate constants for C-4 pseudobase equilibration with each cation. In all cases except W = CN, C-2 pseudobase formation is complete within the mixing time of the stopped-flow instrument.

Substituent effect in electrochemical and ferricyanide oxidations of para-substituted 1-benzyl-3-carbamoyl-1,4-dihydropyridines

1983 ◽  
Vol 48 (5) ◽  
pp. 1408-1421 ◽  
Author(s):  
Františka Pavlíková-Raclová ◽  
Josef Kuthan
Keyword(s):  
Electrochemical Oxidation ◽  
Rate Constants ◽  
Substituent Effect ◽  
Potassium Ferricyanide ◽  
Rotating Disc Electrode ◽  
Disc Electrode ◽  
Rotating Disc ◽  
Half Wave ◽  
Substituted 1 ◽  
Dihydropyridine Derivatives

Half-wave potentials E1/2 of electrochemical oxidation of the title 1,4-dihydropyridine derivatives with the substituents N(CH3)2, OCH3, CH3, H, F, Cl, COOCH3, and CN have been measured on platinum rotating disc electrode in aqueous and anhydrous dimethylformamide, and apparent rate constants k2 of their oxidation with potassium ferricyanide have been measured in water at 298 K. The two quantities (E1/2 and k2) have been correlated both mutually and with empirical σp constants of the substituents. The found correlation relations have been discussed with respect to mechanism of the two transformations investigated.

Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1557-1570 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Ilmar A. Koppel
Keyword(s):  
Kinetic Study ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Substituent Effect ◽  
Substituent Effects ◽  
Alkyl Substituent ◽  
Solvent Parameters ◽  
Substituent Constants ◽  
Hydrolysis Of ◽  
Main Factor

The second-order rate constants k2 (dm3 mol-1 s-1) for the alkaline hydrolysis of substituted alkyl benzoates C6H5CO2R have been measured spectrophotometrically in aqueous 0.5 M Bu4NBr at 50 and 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH, CH2C6H5, CH2CH2Cl, CH2CH2OCH3, CH2CH3) and in aqueous 5.3 M NaClO4 at 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH). The dependence of the alkyl substituent effects on different solvent parameters was studied using the following equations:      ∆ log k = c0 + c1σI + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆EσI + c7∆YσI + c8∆PσI     ∆ log k = c0 + c1σ* + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆Eσ* + c7∆Yσ* + c8∆Pσ* .  ∆ log k = log kR - log kCH3. σI and σ* are the Taft inductive and polar substituent constants. E, Y and P are the solvent electrophilicity, polarity and polarizability parameters, respectively. In the data treatment ∆E = ES - EH2O , ∆Y = YS - YH2O , ∆P = PS - PH2O were used. The solvent electrophilicity, E, was found to be the main factor responsible for changes in alkyl substituent effects with medium. When σI constants were used, variation of the polar term of alkyl substituents with the solvent electrophilicity E was found to be similar to that observed earlier for meta and para substituents, but twice less when σ* constants were used. The steric term for alkyl substituents was approximately independent of the solvent parameters.

Separation of the Enthalpic and Entropic Contributions to Substituent Effects for the Equilibrium Constants of Aromatic Acids

1975 ◽  
Vol 53 (23) ◽  
pp. 3622-3633 ◽  
Author(s):  
T. M. Krygowski ◽  
W. R. Fawcett
Keyword(s):  
Substituent Effect ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Point Of View ◽  
Aromatic Acids ◽  
Resonance Effects ◽  
Equation Analysis ◽  
Reaction Constant ◽  
Enthalpy And Entropy Changes ◽  
Substituent Constants

Separation of the substituent effect ρσ into entropie ρSσS and enthalpic ρHσH contributions is presented within the framework of the general Hammett equation. Analysis of the experimental data for aromatic acids shows that, in general, entropie effects are the major contribution to the total substituent effect, the entropic reaction constant being approximately equal to the normal Hammett ρ A comparison of the present results with those based on a separation of inductive and resonance effects shows that the entropie and inductive effects are directly related. On the other hand, strongly resonance interacting substituents were found to be enthalpy controlled. The substituent effect on enthalpy and entropy changes is discussed from a molecular point of view and related to inductive and resonance effects. A list of 16 enthalpic (σH) and entropie (σS) substituent constants are presented.

scholarly journals Prediction of ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous acetonitrile

2013 ◽  
Vol 11 (12) ◽  
pp. 1964-1975 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Ilmar Koppel
Keyword(s):  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Substituent Effect ◽  
Substituent Effects ◽  
Benzoic Acids ◽  
Aqueous Acetonitrile ◽  
Substituent Constants ◽  
Substituted Benzoic Acids ◽  
Hydrolysis Of ◽  
Ortho Substituent

AbstractThe second-order rate constants k for the alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, in aqueous 50.9% acetonitrile have been measured spectrophotometrically at 25°C. The log k values for meta and para derivatives correlated well with the Hammett σm,p substituent constants. The log k values for ortho-substituted phenyl benzoates showed good correlations with the Charton equation, containing the inductive, σI, resonance, σ○ R, and steric, E s B, and Charton υ substituent constants. For ortho derivatives the predicted (log k X)calc values were calculated with equation (log k ortho)calc = (log k H AN)exp + 0.059 + 2.19σI + 0.304σ○ R + 2.79E s B − 0.0164ΔEσI — 0.0854ΔEσ○ R, where DE is the solvent electrophilicity, ΔE = E AN — E H20 = −5.84 for aqueous 50.9% acetonitrile. The predicted (log k X)calc values for phenyl ortho-, meta- and para-substituted benzoates in aqueous 50.9% acetonitrile at 25°C precisely coincided with the experimental log k values determined in the present work.The substituent effects from the benzoyl moiety and aryl moiety were compared by correlating the log k values for the alkaline hydrolysis of phenyl esters of substituted benzoic acids, X-C6H4CO2C6H5, in various media with the corresponding log k values for substituted phenyl benzoates, C6H5CO2C6H4-X.

Cefoxitin interferes with the "Clini-Skreen" column method for urinary 17-hydroxycorticosteroids.

1987 ◽  
Vol 33 (7) ◽  
pp. 1219-1222
Author(s):  
M H Kroll ◽  
A J Jackson ◽  
R J Elin
Keyword(s):  
Aqueous Solutions ◽  
Absorption Spectra ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Molar Absorptivity ◽  
The Other ◽  
Absorbance Maximum ◽  
Column Method ◽  
Apparent Concentration

Abstract Cefoxitin interferes with determination of urinary 17-hydroxycorticosteroids. The apparent concentration of hormone is increased from three- to 10-fold in samples from patients receiving cefoxitin when the Amberlite XAD-2 "Clini-Skreen" column is used. To determine the mechanism of interference, we reacted aqueous solutions of cefoxitin, cortisol, cortisone, and 11-deoxycortisol with phenylhydrazine; recorded the adsorption spectra; and determined the molar absorptivities and the equilibrium and rate constants. Also, we recorded the absorption spectra of phenylhydrazine with eight other cepha antibiotics and benzylpenicillin. Cortisol, cortisone, 11-deoxycortisol, and cefoxitin react with phenylhydrazine and absorb light with superimposable spectra and absorption maxima of 410 nm. The other antibiotics react with phenylhydrazine but absorbance maxima of the products vary, none being at 410 nm. Cortisol, cortisone, and 11-deoxycortisol react with phenylhydrazine 35-fold faster, have equilibrium constants ninefold greater, and have molar absorptivities 1.6 times that of cefoxitin. Thus, cefoxitin interferes with determination of urinary 17-hydroxycorticosteroids by forming a chromophore with the same absorbance maximum and with a molar absorptivity similar to cortisol, but much more slowly.

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.

scholarly journals Kinetik und Mechanismus der Substitutionsreaktionen von Komplexverbindungen, XLVIII / Kinetics and Mechanism of the Substitution Reactions of Complexes, XLVIII

1975 ◽  
Vol 30 (5-6) ◽  
pp. 393-398 ◽  
Author(s):  
J. Zsakó ◽  
Cs. Várhelyi ◽  
Z. Finta ◽  
J. Kiss-Jakab
Keyword(s):  
Activation Energy ◽  
Aqueous Solutions ◽  
Kinetic Parameters ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Ionic Species ◽  
Protolytic Equilibrium ◽  
Substitution Reactions ◽  
Basic Solutions ◽  
Ph Range

In aqueous solutions the nonelectrolyte [Co(DH)2(NO2)(H2O)] participates in protolytic eqilibria and thus it exists in 7 different forms. Rate constants of the aquation, which leads to the substitution of the nitro group, have been measured in the pH-range between 3.72 and 8 at various temperatures. From these data rate constants, activation energies and entropy values of the aquation of 2 ionic species have been derived, as well as equilibrium constants for the protolytic equilibrium between these species. The kinetic parameters obtained have been compared to those of the aquation of the ionic species which exist in acid and basic solutions and the correlation between structure and activation energy of the aquation has been discussed.

Hydride transfer reactions. Substituent effects in oxidation of N-benzylacridans by π acceptors

1983 ◽  
Vol 61 (11) ◽  
pp. 2544-2551 ◽  
Author(s):  
Allan K. Colter ◽  
Charles C. Lai ◽  
Terry W. Williamson ◽  
Raymond E. Berry
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Second Order ◽  
Face To Face ◽  
Order Rate ◽  
Linear Free Energy ◽  
Donor And Acceptor ◽  
Kinetics Of

The kinetics of oxidation of a series of eight N-(substituted benzyl)acridans (3, NBA's) by 1,4-benzoquinone (BQ), p-chloranil (CA), 2,3-dicyano-1,4-benzoquinone (DCBQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), and tetracyanoethylene (TCNE) in acetonitrile (AN) and by BQ in 50:50 (v/v) AN-water were measured at 25 °C. Equilibrium constants for pseudobase formation, [Formula: see text], from the corresponding acridinium ions (4) were measured in water at 25 °C. Hammett correlations of the second-order rate constants for reaction of the NBA's without ortho substitutents (3a–e) led to ρ values of −0.29 (BQ, AN), −0.55 (CA), −0.56 (DCBQ), −0.64 (TCNQ), −0.41 (TCNE), and −0.47 (BQ, 50:50 AN–water). The second-order rate constants for 3a–e also give good linear free energy correlations with the [Formula: see text] values of 4a–e. These correlations and the [Formula: see text] values for the ortho-substituted acridinium ions (4f, g, h) are used to calculate rate constants for oxidation of the corresponding ortho-substituted NBA's (3f, g, h). The rate constants calculated in this way are 4.7 to 6.6 times and 6.4 to 12 times larger, respectively, than the observed rate constants for N-(2,4,6-trimethylbenzyl) and N-(2,6-dichlorobenzyl)acridan (3g and h). The variations in ρ values are attributed mainly to differences in the amount of electrostatic stabilization in the transition state resulting from differences in the separation of donor and acceptor and the degree of delocalization of the negative charge. The rate retarding effect of a pair of ortho substituents is attributed to sterie effects in a preferred face-to-face transition state.

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