Indirect measurement of the rate constants for the diazotisation of substituted anilines by nitrosyl chloride and nitrosyl thiocyanate

1977 ◽  
pp. 502 ◽  
Author(s):  
D. Lyn H. Williams
Keyword(s):  
Rate Constants ◽  
Indirect Measurement ◽  
Nitrosyl Chloride ◽  
Substituted Anilines

A STUDY OF PROTON EXCHANGE REACTIONS OF SUBSTITUTED ANILINES IN TRIFLUOROACETIC ACID

1964 ◽  
Vol 42 (12) ◽  
pp. 2641-2656 ◽  
Author(s):  
W. F. Reynolds ◽  
T. Schaefer
Keyword(s):  
Trifluoroacetic Acid ◽  
Rate Constants ◽  
Ion Pair ◽  
Proton Exchange ◽  
Free Energies ◽  
Exchange Reactions ◽  
Kcal Mole ◽  
Substituted Anilines ◽  
Ionic Reaction ◽  
Acid Proton

The acid proton exchange rates of solutions of some halo-substituted anilines in trifluoroacetic acid have been determined by measuring the acid proton signal width. In addition, the proton exchange rate of protonated N,N-dimethylaniline in trifluoroacetic acid is discussed. It is suggested that proton exchange occurs via the following reaction:[Formula: see text]The reaction is believed to occur in two steps: the oppositely charged ions form ion pairs which then transfer protons internally. Experimental evidence indicates that the ion–pair dissociation constant is less than, or equal to, one.The activation energies range from 10 to 24 kcal/mole. The rate constants at 25 °C for a possible bi-ionic reaction are calculated. Ionic activity coefficients are estimated by the Debye–Hückel equation. Another set of rate constants is calculated, assuming that the ions exist partly or completely as ion pairs.The free energies, enthalpies, and entropies of activation are calculated for an ion-pair reaction and for an overall bi-ionic reaction. The free energies of activation range from 10 to 17 kcal/mole and for haloanilines are less than that of aniline. In the ortho- and para-substituted anilines, ΔF≠, in general, decreases with decreasing halogen electronegativity. ΔF≠ values for metasubstituted anilines decrease with increasing substituent electronegativity. ΔF≠ values are largest for parahaloanilines and smallest for orthohaloanilines. The ΔF≠ values for haloanilines can be rationalized by reasonable combinations of inductive and mesomeric effects. The values of entropies of activation are determined largely by the positions of the substituents. ΔS≠ values range from 35 to −10 entropy units (e.u.) with aniline and para-substituted anilines having the largest positive values and orthosubstituted anilines having negative values. The value of ΔF≠ for protonated N,N-dimethylaniline is larger than that for protonated aniline, as would be expected. ΔS≠ is quite small. This is attributed to steric hindrance of solvation of the dimethylanilinium ion.

scholarly journals INFLUENCE OF SUBSTITUTES ON THE RATE OF REACTION OF SUBSTITUTED ANILINES WITH A BENZOIC ACID, CATALYZED BY POLYBUTOXYTITANATES

2020 ◽  
Vol 86 (1) ◽  
pp. 36-59
Author(s):  
Leon Shteynberg
Keyword(s):  
Benzoic Acid ◽  
Rate Constants ◽  
Atmospheric Oxygen ◽  
Titanium Atom ◽  
Electron Acceptors ◽  
Hammett Equation ◽  
Substituted Anilines ◽  
Strong Electron ◽  
Oxidation Processes ◽  
Carbonyl Bond

The catalytic production of benzanilide by the interaction of benzoic acid with aniline is an important model process recently intensively developed in the field of the concept of «green chemistry», direct catalytic amidation, and its study is an urgent scientific and practical task.  To solve this problem, the effect of substituents in the aniline core on the catalysis by polybut-oxytitanates on acylation of substituted  anilines  by benzoic  acid  was  studied. The rate constants of this the second-order reaction (the first with respect to substituted aniline and benzoic acid; boiling ortho-xylene, 145 °С, nitrogen flow)  are well correlated according to the Hammett equation with three straight lines for individual groups of substituents with ρ = –0.86 (electron donors), 1.12 (weak electron acceptors),  –2.83 (strong  electron  acceptors). To explain this dependence, a variant of the catalytic amidation mechanism is proposed, which takes into account the formation of titanium butoxybenzoates in the first minutes of the reaction — a true  amidation  catalyst;  coordination (polarization of the carbonyl bond in the interaction with the catalyst titanium atom) and acid (polarization of the carbonyl bond in the interaction with the complex of the formed substitu- ted benzanilide with the titanium butoxyben-zoates)  catalysis   routes. Inhibition of the catalytic reaction is associated with the presence in the mass of water, relative excess of  benzoic acid and a possible amide–imide tautomerism of substituted benzanilides, accompanied by the interaction of the imide form of the latter with titanium  butoxybenzoates, which does not lead to the route of acid catalysis. The rate constants for catalytic acylation of substituted anilines, containing  electron-donating substituents, with benzoic acid in the  air are correlated according to the Hammett equation by a straight line segment with ρ = 0.99, which is associated with the predominant influence  of  the  oxidation  processes  of  the  corresponding   amines. Catalytic acylation under comparable conditions of substituted anilines, containing electron-withdrawing substituents, oxidation processes due to atmospheric  oxygen  have  little  effect  on.

scholarly journals Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

2013 ◽  
Vol 9 ◽  
pp. 1620-1629 ◽  
Author(s):  
Andreas Gansäuer ◽  
Meriam Seddiqzai ◽  
Tobias Dahmen ◽  
Rebecca Sure ◽  
Stefan Grimme
Keyword(s):  
Rate Constants ◽  
Activation Barrier ◽  
Computational Study ◽  
Theoretical Data ◽  
Radical Addition ◽  
Radical Center ◽  
Substituted Anilines ◽  
London Dispersion ◽  
Reaction Barriers ◽  
Experimental Values

The intramolecular radical addition to aniline derivatives was investigated by DFT calculations. The computational methods were benchmarked by comparing the calculated values of the rate constant for the 5-exo cyclization of the hexenyl radical with the experimental values. The dispersion-corrected PW6B95-D3 functional provided very good results with deviations for the free activation barrier compared to the experimental values of only about 0.5 kcal mol−1 and was therefore employed in further calculations. Corrections for intramolecular London dispersion and solvation effects in the quantum chemical treatment are essential to obtain consistent and accurate theoretical data. For the investigated radical addition reaction it turned out that the polarity of the molecules is important and that a combination of electrophilic radicals with preferably nucleophilic arenes results in the highest rate constants. This is opposite to the Minisci reaction where the radical acts as nucleophile and the arene as electrophile. The substitution at the N-atom of the aniline is crucial. Methyl substitution leads to slower addition than phenyl substitution. Carbamates as substituents are suitable only when the radical center is not too electrophilic. No correlations between free reaction barriers and energies (ΔG ‡ and ΔG R) are found. Addition reactions leading to indanes or dihydrobenzofurans are too slow to be useful synthetically.

scholarly journals INFLUENCE OF SUBSTITUTES ON THE RATE OF THE REACTION OF ORTHOSUBSTITUTED BENZOIC ACIDS WTH ANILINE, CATALYZED BY POLYBUTOXYTITANATES

2021 ◽  
Vol 87 (3) ◽  
pp. 18-40
Author(s):  
Leon Shteinberg
Keyword(s):  
Benzoic Acid ◽  
Rate Constants ◽  
Nucleophilic Attack ◽  
Benzoic Acids ◽  
Substituted Anilines ◽  
Hydrogen Atoms ◽  
Active Centers ◽  
Straight Line ◽  
Catalytically Active ◽  
Substituted Benzoic Acids

The polybutoxytitanates catalysis of aniline acylation by orthosubstituted benzoic acids leads to the production of substituted benzanilides. Catalytic rate constants of the second order reaction (the first with respect to aniline and ortho-substituted benzoic acid; boiling ortho=xylene, 145°C) correlate well according to the Hammett and Bronsted equations with straight line segments with ρ=1.93 and α=0.66, in contrast to the reaction of aniline with meta- and parasubstituted benzoic acids and substituted anilines with benzoic acid. This dependence drops out 2=nitrobenzoic and 1=naphthoic acids, which have relatively low reactivity and the greatest steric hindrances both for nucleophilic attack by aniline and for possible coordination with catalytically active centers of the corresponding ortho-substituted titanium polybutoxybenzoates formed in situ. Based on these data, the previously proposed mechanism of bifunctional catalysis due to titanium polybutoxybenzoates and their complexes with meta- and parasubstitutedbenzanilides was supplemented by the possibility of the steric inhibition of reaction by the most bulky substituents and chelate structures formation of orthosubstituted benzoic acids and their anilides with individual titanium atoms of the catalyst, as well as the simulta­neous H-bonding of the amino group hydrogen atoms of aniline, which leads to its activation to a nucleophilic attack, with a carbonyl group and an orthopositioned substituent of the orthobenzoate ligand in the coordination sphere of titanium. Taking into account such chelation and steric barriers, as well as inhibition of acid catalysis due to the formation of the imide form of anilides, containing electron-withdrawing substituents, the equations for the rate constants of the catalytic reaction of ortho-substituted benzoic acids with aniline are derived, corresponding to the experimentally obtained Hammett dependence.

Inhibition in Purified Systems and in Human Plasma of Chimaeric Plasminogen Activators Consisting of the NH2-Terminal Region of Tissue-Type Plasminogen Activator and the COOH-Terminal Region of UrokinaseType Plasminogen Activator

1988 ◽  
Vol 60 (02) ◽  
pp. 247-250 ◽  
Author(s):  
H R Lijnen ◽  
L Nelles ◽  
B Van Hoef ◽  
F De Cock ◽  
D Collen
Keyword(s):  
Plasminogen Activator ◽  
Rate Constants ◽  
Plasminogen Activators ◽  
Second Order ◽  
Tissue Type ◽  
Single Chain ◽  
Chain Molecules ◽  
Order Rate ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator

SummaryRecombinant chimaeric molecules between tissue-type plasminogen activator (t-PA) and single chain urokinase-type plasminogen activator (scu-PA) or two chain urokinase-type plasminogen activator (tcu-PA) have intact enzymatic properties of scu-PA or tcu-PA towards natural and synthetic substrates (Nelles et al., J Biol Chem 1987; 262: 10855-10862). In the present study, we have compared the reactivity with inhibitors of both the single chain and two chain variants of recombinant u-PA and two recombinant chimaeric molecules between t-PA and scu-PA (t-PA/u-PA-s: amino acids 1-263 of t-PA and 144-411 of u-PA; t-PA/u-PA-e: amino acids 1-274 of t-PA and 138-411 of u-PA). Incubation with human plasma in the absence of a fibrin clot for 3 h at 37° C at equipotent concentrations (50% clot lysis in 2 h), resulted in significant fibrinogen breakdown (to about 40% of the normal value) for all two chain molecules, but not for their single chain counterparts. Preincubation of the plasminogen activators with plasma for 3 h at 37° C, resulted in complete inhibition of the fibrinolytic potency of the two chain molecules but did not alter the potency of the single chain molecules. Inhibition of the two chain molecules occurred with a t½ of approximately 45 min. The two chain variants were inhibited by the synthetic urokinase inhibitor Glu-Gly-Arg-CH2CCl with apparent second-order rate constants of 8,000-10,000 M−1s−1, by purified α2-antiplasmin with second-order rate constants of about 300 M−1s−1, and by plasminogen activator inhibitor-1 (PAI-1) with second-order rate constants of approximately 2 × 107 M−1s−1.It is concluded that the reactivity of single chain and two chain forms of t-PA/u-PA chimaers with inhibitors is very similar to that of the single and two chain forms of intact u-PA.

Effect of Calcium ion on the interaction between Thrombin and Heparin. Thermal Denaturation

1977 ◽  
Vol 38 (03) ◽  
pp. 0677-0684 ◽  
Author(s):  
Raymund Machovich ◽  
Péter Arányi
Keyword(s):  
Calcium Ions ◽  
Rate Constants ◽  
Thermal Denaturation ◽  
Time Course ◽  
Complex Analysis ◽  
Heat Inactivation ◽  
Second Phase ◽  
Denaturation Kinetics ◽  
Enzyme Protection ◽  
Enzyme Denaturation

SummaryHeat inactivation of thrombin at 54° C followed first order kinetics with a rate constant of 1.0 min−1 approximately. Addition of heparin resulted in protection against thermal denaturation and, at the same time, rendered denaturation kinetics more complex. Analysis of the biphasic curve of heat inactivation in the presence of heparin revealed that the rate constants of the second phase changed systematically with heparin concentrations. Namely, at 4.5 × 10−6M, 9 × 10−6M, 1.8 × 10−5M and 3.6 × 10−5M heparin concentrations, the rate constants were 0.27 min−1, 0.17 min−1, 0.11 min−1 and 0.06 min−1, respectively.Sulfate as well as phosphate ions displayed also enzyme protection against heat inactivation, however, the same effect was obtained already at a heparin concentration, lower by three orders of magnitude.The kinetics of enzyme denaturation was not affected by calcium ions, whereas in the presence of heparin the inactivation rate of thrombin changed, i. e. calcium ions abolished the biphasic character of time course of thermal denaturation.Thus, the data suggest that calcium ions contribute to the effect of heparin on thrombin.

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