Kinetics and Mechanism of the 2+ 2 Cycloaddition of Tetracyanoethylene to 2,5-Dimethyl-2,4-Hexadiene

1988 ◽  
Vol 43 (5) ◽  
pp. 435-441 ◽  
Author(s):  
Adel N. Asaad ◽  
Gunnar Aksnes
Keyword(s):  
Complex Formation ◽  
Transition State ◽  
Thermodynamic Parameters ◽  
Cycloaddition Reaction ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Kinetics And Mechanism ◽  
Eda Complex ◽  
Kinetics Of ◽  
Cyclobutane Derivative

The kinetics of the 2 + 2 cycloaddition reaction between tetracyanoethylene and 2,5-dimethyl- 2,4-hexadiene in different solvents has been studied by following the disappearance of the intermediate EDA-complex spectrophotometrically. It is concluded that the EDA-complex is transformed through a concerted cyclicpolar transition state to give the vinyl cyclobutane derivative (III). The effects of various solvents on the reaction rates have been analysed using a multiparameter approach. The thermodynamic parameters (ΔH0 and ΔS0), of EDA-complex formation and the activation parameters (ΔH# and ΔS#) of the cycloaddition have been discussed.

Kinetics and mechanism of the reaction of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione

1990 ◽  
Vol 55 (8) ◽  
pp. 1984-1990 ◽  
Author(s):  
José M. Hernando ◽  
Olimpio Montero ◽  
Carlos Blanco
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Activation Parameters ◽  
Enol Form ◽  
Kinetics And Mechanism ◽  
Kinetic Constants ◽  
Steric Factors ◽  
Kinetics Of ◽  
Mechanism Of The Reaction

The kinetics of the reactions of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione to form the corresponding monocomplexes have been studied spectrophotometrically in the range 5 °C to 16 °C at I 25 mol l-1 in aqueous solution. In the proposed mechanism for the two complexes, the enol form reacts with the metal ion by parallel acid-independent and inverse-acid paths. The kinetic constants for both pathways have been calculated at five temperatures. Activation parameters have also been calculated. The results are consistent with an associative activation for Fe(H2O)63+ and dissociative activation for Fe(H2O)5(OH)2+. The differences in the results for the complexes of heptanediones studied are interpreted in terms of steric factors.

scholarly journals Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Khémesse Kital ◽  
Moumouny Traoré ◽  
Diégane Sarr ◽  
Moussa Mbaye ◽  
Mame Diabou Gaye Seye ◽  
...  
Keyword(s):  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Initial Rate ◽  
Reaction Medium ◽  
Standard Entropy ◽  
Step Size ◽  
Formation Reaction ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Complex Formation Process

Abstract The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

Solvolysis of isopropyl bromide in ethanol–water mixtures. Dissection into initial state and transition state contributions

1976 ◽  
Vol 54 (24) ◽  
pp. 3944-3948 ◽  
Author(s):  
Wiendelt Drenth ◽  
Michael Cocivera
Keyword(s):  
Vapor Pressure ◽  
Transition State ◽  
Thermodynamic Parameters ◽  
Activation Parameters ◽  
Solvent Composition ◽  
Initial State ◽  
Partial Vapor Pressure ◽  
State Variation

Rates were determined for the solvolysis of isopropyl bromide in ethanol–water mixtures (20 to 80% by volume of ethanol) at 50 and 75 °C and the corresponding activation parameters calculated. From the partial vapor pressure of isopropyl bromide over the various solutions at 50 and 75 °C, the variations in its initial state thermodynamic parameters were calculated. Thus, the variation in the activation parameters with solvent composition could be analyzed in terms of initial and transition state contributions. The initial state variation dominates according to a unimolecular as well as to a bimolecular treatment of data.

scholarly journals Reactivity of Phenol and Aniline towards Quinolinium Chloro Chromate: A Comparative Oxidation Kinetic Study

2015 ◽  
Vol 59 ◽  
pp. 81-92
Author(s):  
Seplapatty Kalimuthu Periyasamy ◽  
H. Satham Hussain ◽  
R. Manikandan
Keyword(s):  
Oxidation Kinetic ◽  
Activation Parameters ◽  
Dipole Interaction ◽  
Reaction Rates ◽  
Hydrogen Ion ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
First Order ◽  
Different Temperatures ◽  
Kinetics Of

The kinetics of Oxidation of Phenol and aniline by quinolinium Chlorochromate (QCC) in aqueous acetic acid medium leads to the formation of quinone and azobenzene respectively. The reactions are first order with respect to both Phenol and aniline. The reaction is first order with respect to quinolinium chlorochromate (QCC) and is catalyzed by hydrogen ion. The hydrogen-ion dependence has the form: kobs = a+b [H+]. The rate of oxidation decreases with increasing dielectric constant of solvent, indicating the presence of an ion-dipole interaction. The reaction does not induced the polymerization of acrylonitrile. The retardation of the rate by the addition of Mn2+ ions confirms that a two electron transfer process is involved in the reaction. The reaction rates have been determined at different temperatures and the activation parameters have been calculated. From the above observations kinetic results a probable mechanism have been proposed.

A KINETICS AND MECHANISTIC STUDY OF THE OXIDATION OF L-ARGININE BY QDC IN DMF-WATER MEDIUM

2021 ◽  
pp. 11-12
Author(s):  
Deepika Jain ◽  
Shilpa Rathor
Keyword(s):  
Perchloric Acid ◽  
Reaction Rate ◽  
Main Product ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Mechanistic Study ◽  
Water Medium ◽  
Volume Percentage ◽  
Kinetics Of Oxidation ◽  
Kinetics Of

The present paper describes the kinetics of oxidation of l-Arginine by QDC in the presence of perchloric acid in 30% DMF-H O(v/v) medium at 2 + 40⁰C spectrophotometrically at λ =354nm. The reaction is rst order with respect to [QDC], [H ], and [substrate]. The reaction rate increased with max increasing volume percentage of DMF in reaction mixture. Michaelis- Menten type kinetic was observed with l-Arginine. The reaction rates were studied at different temperature and the activation parameters has been computed. The main product was identied as Cr (III) and 4-Guanidino buteraldehyde.

Kinetics of hydrosilylation of tert-butylphenylketone by diphenylsilane catalysed by [Rh(1,5-COD)(-)-DIOP]+ClO-4

1980 ◽  
Vol 45 (8) ◽  
pp. 2224-2239 ◽  
Author(s):  
Ivan Kolb ◽  
Jiří Hetflejš
Keyword(s):  
Activation Parameters ◽  
Reaction Rates ◽  
Reaction Model ◽  
Initial Reaction ◽  
Title Reaction ◽  
Rate Determining Step ◽  
Kinetic Isotope ◽  
Arene Complex ◽  
Kinetics Of

Kinetic analysis of the title reaction has been made by the method of initial reaction rates. On the basis of the rate data, kinetic isotope effect and spectroscopic study of the reaction of the organosilicon hydride with the catalyst, the reaction model was proposed involving the following steps: the displacement of the diene by reaction with the silicon hydride from a rhodium-arene complex in an induction period of the hydrosilylation, the oxidative addition of the organosilicon hydride to the rhodium-arene complex, followed by the interaction of the ketone with the silylhydridorhodium (III) species in the rate determining step. The process is characterized by the following activation parameters: ΔU = 54.5 ± 8.5 kJ mol-1 and ΔS = -88± 25 J mol-1.K-1. The significant role of the entropic factor was supported by the analysis of the temperature dependence of the asymmetric efficiency of the catalyst.

Kinetics and mechanism of aminolysis of (Z)-4-arylidene-2-phenyl-5(4H)oxazolones

1992 ◽  
Vol 70 (10) ◽  
pp. 2515-2519 ◽  
Author(s):  
Sharifa S. Alkaabi ◽  
Ahmad S. Shawali
Keyword(s):  
Rate Constants ◽  
Activation Parameters ◽  
Order Conditions ◽  
Kinetics And Mechanism ◽  
Hammett Equation ◽  
Third Order ◽  
First Order ◽  
Different Temperatures ◽  
Pseudo First Order ◽  
Kinetics Of

The kinetics of the reactions of a series of (Z)-4-arylidene-2-phenyl-5(4H)oxazolones 1 with n-butylamine and piperidine were studied spectrophotometrically in dioxane, ethanol, and cyclohexane under pseudo-first-order conditions and at different temperatures. The relation k1(obs) = k2[amine] + k3[amine]2 was found applicable for all reactions studied in either dioxane or ethanol. However, in cyclohexane the n-butylaminolysis of 1 followed only third-order kinetics k1(obs) = k3[n-BuNH2]2. The kinetics of the reaction of 1 with n-butylamine in the presence of catalytic amounts of triethylamine in dioxane followed the equation: k1(obs)k2 = [n-BuNH2] + k3[n-BuNH2]2[Formula: see text] [Et3N]. The rate constants k2 and k3 correlated well with the Hammett equation and the corresponding activation parameters were determined. The results were interpreted in terms of a mechanism involving solvent- and amine-catalyzed processes.

Kinetics of Proton Transfer Reactions of Carbon Acids. II. Reaction of Di-(4-nitrophenyl)methane with Alkoxide Bases

1972 ◽  
Vol 50 (1) ◽  
pp. 24-30 ◽  
Author(s):  
A. Jarczewski ◽  
K. T. Leffek
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Rate Constants ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Activation Process ◽  
Proton Transfers ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Kinetics Of

The second-order rate constants have been measured over a range of temperatures for the proton-transter reactions from di-(4-nitrophenyl)methane to ethoxide, isopropoxide, and t-butoxide ions in solvents consisting of the corresponding alcohols containing 10% toluene by volume. The activation parameters ΔH≠ and ΔS≠ have been calculated and an interpretation of them is given in terms of solvation effects during the activation process. A comparison between the activation parameters for proton transfers and E2 olefin-forming β-elimination reactions is made and discussed with respect to transition state character of the latter reactions.

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