Tautomerism of 5-nitro-2-furylnitromethane

1981 ◽  
Vol 46 (12) ◽  
pp. 3122-3127
Author(s):  
Iva Sroková ◽  
Pavel Vetešník ◽  
Adolf Jurášek ◽  
Jaroslav Kováč
Keyword(s):  
Kinetic Study ◽  
Temperature Dependence ◽  
Thermodynamic Parameters ◽  
Rate Constants ◽  
Strong Acid ◽  
Ion Pair ◽  
Aprotic Solvents ◽  
Protic Solvents ◽  
Parallel Reactions ◽  
Experimental Values

UV study of properties of 5-nitro-2-furylnitromethane (I) in various solvents has shown that this compound is a very strong acid (pKa 3.98) forming an ion pair in protic solvents (water, alcohols) and existing exclusively as nitro-form in aprotic solvents (tetrachloromethane, chloroform, n-hexane, diethyl ether, dioxane). Kinetic study of tautomerism in water has given experimental values of combined rate constants of parallel reactions. Thermodynamic parameters of the tautomeric transformations have been calculated from temperature dependence of the rate constants.

scholarly journals Reactivity of cyclohex-1-enylcarboxylic and 2-methylcyclohex-1-enylcarboxylic acids with diazodiphenylmethane in aprotic solvents

2000 ◽  
Vol 65 (12) ◽  
pp. 839-846
Author(s):  
Jasmina Nikolic ◽  
Gordana Uscumlic ◽  
Vera Krstic
Keyword(s):  
Hydrogen Bond ◽  
Rate Constants ◽  
Kinetic Data ◽  
Linear Regression Analysis ◽  
Spectroscopic Method ◽  
Reaction Rates ◽  
Aprotic Solvents ◽  
Experimental Conditions ◽  
Hydrogen Bond Acceptor ◽  
Protic Solvents

Rate constants for the reaction of diazodiphenylmethane with cyclohex-1-enylcarboxylic acid and 2-methylcyclohex-1-enylcarboxylic acid were determined in nine aprotic solvents, as well as in seven protic solvents, at 30?C using the appropriate UV-spectroscopic method. In protic solvents the unsubsituted acid displayed higher reaction rates than the methyl-substituted one. The results in aprotic solvents showed quite the opposite, and the reaction rates were considerably lower. In order to explain the obtained results through solvent effects, reaction rate constants (k) of the examined acids were correlated using the total solvatochromic equation of the form: log k=logk0+s?*+a?+b?, where ?* is the measure of the solvent polarity, a represents the scale of the solvent hydrogen bond donor acidities (HBD) and b represents the scale of the solvent hydrogen bond acceptor basicities (HBA). The correlation of the kinetic data were carried out by means of multiple linear regression analysis and the opposite effects of aprotic solvents, as well as the difference in the influence of protic and aprotic solvents on the reaction of the two examined acids with DDM were discussed. The results presented in this paper for cyclohex-1-enylcarboxylic and 2-methylcyclohex-1-enylcarboxylic acids were compared with the kinetic data for benzoic acid obtained in the same chemical reaction, under the same experimental conditions.

Reactivity of nucleophiles in dimethyl sulfoxide and its comparison with nucleophilic reactivity in protic medium

1989 ◽  
Vol 54 (10) ◽  
pp. 2715-2720 ◽  
Author(s):  
Vítězslav Zima ◽  
Oldřich Pytela ◽  
Jaromír Kaválek ◽  
Miroslav Večeřa
Keyword(s):  
Dimethyl Sulfoxide ◽  
Electrostatic Interaction ◽  
Rate Constants ◽  
Reaction Medium ◽  
Correlation Equation ◽  
Regression Coefficients ◽  
Aprotic Solvents ◽  
Protic Solvents ◽  
Nucleophilic Reactivity

Reactions of 2,4-dinitrophenyl acetate and 2,4-dinitrofluorobenzene as model substrates with 12 nucleophiles have been studied in dimethyl sulfoxide. The rate constants obtained have been discussed with regard to the nucleophilic reactivity differences in dimethyl sulfoxide and protic solvents inclusive of the different manifestation of the charge of nucleophiles. The applicability of an earlier-suggested correlation equation to the data obtained has been verified. The reaction medium markedly affects the reactivity of nucleophiles, the effect of charge being substantially greater in aprotic solvents (electrostatic interaction) than in protic ones (solvation). In spite of these differences the correlation with application of an empirical nucleophilicity scale suggested earlier is satisfactory, the regression coefficients obtained reflect changes in the nature of medium.

scholarly journals Investigations of the reactivity of pyridine carboxylic acids with diazodiphenylmethane in protic and aprotic solvents, Part I: Pyridine mono-carboxylic acids

2005 ◽  
Vol 70 (4) ◽  
pp. 557-567 ◽  
Author(s):  
Aleksandar Marinkovic ◽  
Sasa Drmanic ◽  
Bratislav Jovanovic ◽  
Milica Misic-Vukovic
Keyword(s):  
Carboxylic Acids ◽  
Rate Constants ◽  
Kinetic Data ◽  
Reaction Rate ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Aprotic Solvents ◽  
Solvent Parameters ◽  
Protic Solvents ◽  
Pyridine Carboxylic

Rate constants for the reaction of diazodiphenylmethane with isomeric pyridine carboxylic acids were determined in chosen protic and aprotic solvents at 30 ?C, using the well known UV spectrophotometric method. The values of the rate constants of the investigated acids in protic solvents were higher than those in aprotic solvents. The second order rate constants were correlated with solvent parameters using the Kamlet-Taft solvatochromic equation in the form: logk = logk0 + s?*+ a? + b?. The correlation of the obtained kinetic data were performed by means of multiple linear regression analysis taking appropriate solvent parameters. The signs of the equation coefficients were in agreement with the postulated reaction mechanism. The mode of the influence of the solvent on the reaction rate in all the investigated acids are discussed on the basis of the correlation results.

OH radicals reactivity towards phenol-related pollutants in water: temperature dependence of the rate constants and novel insights into the [OH–phenol]˙ adduct formation

2020 ◽  
Vol 22 (3) ◽  
pp. 1324-1332 ◽  
Author(s):  
Ana Kroflič ◽  
Thomas Schaefer ◽  
Matej Huš ◽  
Hoa Phuoc Le ◽  
Tobias Otto ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Transition State ◽  
Kinetic Study ◽  
Temperature Dependence ◽  
Water Temperature ◽  
Aqueous Phase ◽  
State Formation ◽  
Rate Constants ◽  
Adduct Formation ◽  
Oh Radicals

Relevance: a kinetic study on aqueous-phase reactions between OH˙ and phenolic compounds reveals structure-related differences in the transition state formation.

scholarly journals Effects of solvent and structure on the reactivity of 6-substituted nicotinic acids with diazodiphenylmethane in aprotic solvents

2009 ◽  
Vol 74 (12) ◽  
pp. 1359-1370 ◽  
Author(s):  
Sasa Drmanic ◽  
Aleksandar Marinkovic ◽  
Bratislav Jovanovic
Keyword(s):  
Rate Constants ◽  
Substituent Effect ◽  
Reaction Rate ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Aprotic Solvents ◽  
Solvent Interaction ◽  
Protic Solvents ◽  
Linear Solvation Energy ◽  
Nucleophilic Solvation

The rate constants for the reactions of diazodiphenylmethane (DDM) with 6-substituted nicotinic acids in aprotic solvents at 30?C were determined. The obtained second order rate constants in aprotic solvents, together with literature data for benzoic and nicotinic acids in protic solvents, were used for the calculation of solvent effects, employing the Kamlet-Taft solvatochromic equation (linear solvation energy relationship - LSER) in the form: log k = log k0 + + s?*+ a? + b?. The correlations of the kinetic data were performed by means of multiple linear regression analysis taking appropriate solvent parameters. The sign of the equation coefficients (s, a and b) were in agreement with the postulated reaction mechanism, and the mode of the solvent influences on the reaction rate is discussed based on the correlation results. A similar contribution of the non-specific solvent effect and electrophilic solvation was observed for all acids, while the highest contribution of nucleophilic solvation was influenced by their high acidity. Correlation analysis of the rate data with substituent ?p parameters in an appropriate solvent using the Hammett equation was also performed. The substituent effect on the acid reactivity was higher in aprotic solvents of higher dipolarity/polarizability. The mode of the transmission of the substituent effect is discussed in light of the contribution of solute-solvent interaction on the acid reactivity.

Oxidation of (1-hydroxybenzyl)ferrocene and its derivatives substituted in phenyl ring with bis(triphenylsilyl) chromate

1982 ◽  
Vol 47 (12) ◽  
pp. 3375-3380 ◽  
Author(s):  
Jaroslav Holeček ◽  
Karel Handlíř ◽  
Milan Nádvorník ◽  
Milan Vlček
Keyword(s):  
Linear Dependence ◽  
Rate Constants ◽  
Oxidation Rate ◽  
Phenyl Ring ◽  
Equilibrium Constants ◽  
Aprotic Solvents ◽  
Protonation Equilibrium ◽  
Oxidation Of Alcohols ◽  
Hammett Σ Constants ◽  
Sulphuric Acid Medium

Kinetics have been studied of oxidation of (1-hydroxybenzyl)ferrocenes substituted in phenyl ring with bis(triphenylsilyl) chromate in benzene solutions as well as protonation of these alcohols in sulphuric acid medium. Logarithms of the oxidation rate constants (kobs, 20-40 °C) and those of the protonation equilibrium constants (KR+, 25 °C) show linear dependence on the Hammett σ constants, the ρ constant values being -0.86 to -0.40 and -2.50, respectively. These negative values suggest that the both processes are influenced by the same effects and confirm the mechanism proposed earlier for oxidation of alcohols with ferrocenyl substituent by action of bis(triphenylsilyl) chromate in aprotic solvents.

Salt effect in hydrolysis of 3-acyl-1,3-diphenyltriazenes

1981 ◽  
Vol 46 (12) ◽  
pp. 3104-3109 ◽  
Author(s):  
Miroslav Ludwig ◽  
Oldřich Pytela ◽  
Miroslav Večeřa
Keyword(s):  
Sodium Chloride ◽  
Temperature Dependence ◽  
Potassium Chloride ◽  
Rate Constants ◽  
Zinc Sulphate ◽  
Salt Effect ◽  
Sodium Sulphate ◽  
Potassium Sulphate ◽  
Lithium Sulphate ◽  
Hydrolysis Of

Rate constants of non-catalyzed hydrolysis of 3-acetyl-1,3-diphenyltriazene (I) and 3-(N-methylcarbamoyl)-1,3-diphenyltriazene (II) have been measured in the presence of salts (ammonium chloride, potassium chloride, lithium chloride, sodium chloride and bromide, ammonium sulphate, potassium sulphate, lithium sulphate, sodium sulphate and zinc sulphate) within broad concentration ranges. Temperature dependence of the hydrolysis of the substrates studied has been measured in the presence of lithium sulphate within temperature range 20° to 55 °C. The results obtained have been interpreted by mechanisms of hydrolysis of the studied substances.

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