Studies on the decomposition of tetra-alkylammonium salts in solution. Part II. Dependence of the activation parameters on the structure of the substrate

1969 ◽  
Vol 47 (20) ◽  
pp. 3725-3728 ◽  
Author(s):  
J. T. Burns ◽  
K. T. Leffek
Keyword(s):  
Free Energy ◽  
Nitrogen Atom ◽  
Tertiary Amine ◽  
Chloroform Solution ◽  
Activation Parameters ◽  
Decomposition Reaction ◽  
Energy Correlation ◽  
Entropy Of Activation ◽  
Alkylammonium Salts ◽  
Enthalpy And Entropy

The enthalpy and entropy of activation for the decomposition reaction of seven tetra-alkylammonium iodides in chloroform solution have been measured. All the salts contained the benzyl group attached to the nitrogen atom and decomposed to yield benzyl iodide and a tertiary amine as the only products.A Hammett free energy correlation is made and used to deduce the nature of the transition state, and a rationalization of the variation of the enthalpy and entropy of activation with the structure of the substrate is given.

Dielectric relaxation of some aliphatic ketones in dilute solutions

1976 ◽  
Vol 54 (7) ◽  
pp. 794-799 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Free Energy ◽  
Relaxation Time ◽  
Dielectric Relaxation ◽  
Relaxation Mechanism ◽  
Relaxation Data ◽  
Nonpolar Solvents ◽  
Aliphatic Ketones ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy ◽  
Dielectric Relaxation Behavior

The dielectric relaxation behavior of 2-butanone, 2-pentanone, 2-heptanone, and 3-nonanone in dilute nonpolar solvents, n-heptane, cyclohexane, benzene, and carbon tetrachloride has been studied in the microwave region at a number of temperatures. The relaxation data have been used to estimate the free energy, enthalpy, and entropy of activation for the relaxation mechanism. The values of the relaxation time for those solutions for which there are available known data agree well with other determinations. The results have been discussed in terms of dipole reorientation by intramolecular and overall molecular rotation and compared, wherever possible, with other similar studies on aliphatic molecules.

Studies on the decomposition of tetra-alkylammonium salts in solution. Part III: Interpretation of Hammett correlations

1970 ◽  
Vol 48 (12) ◽  
pp. 1865-1868 ◽  
Author(s):  
E. C. F. Ko ◽  
K. T. Leffek
Keyword(s):  
Free Energy ◽  
Nitrogen Atom ◽  
Phenyl Group ◽  
Acetone Solution ◽  
Reaction Site ◽  
Decomposition Reactions ◽  
Linear Plot ◽  
Alkylammonium Salts ◽  
Alkylammonium Halides

Hammett free energy correlations are reported for the decomposition reactions of tetra-alkylammonium halides in chloroform and acetone solution. All the salts contained a substituted benzyl group attached to the nitrogen atom and decomposed to yield a benzyl iodide and dimethylaniline as the only products.The curved Hammett plots for para-substituted benzyl compounds are compared to the linear plot found previously for a series of salts each containing a para-substituted phenyl group, and it is concluded that curved Hammett plots cannot be used as evidence for a change of mechanism, unless direct conjugative effects between substituent and reaction site are absent.

scholarly journals Activation Parameters for Inversion of 1-(1-Naphthyl)-isoquinoline. II. Determination of the Enthalpy and Entropy of Activation for the Free Base.

1974 ◽  
Vol 28a ◽  
pp. 213-216 ◽  
Author(s):  
Jörgen R. Pedersen ◽  
Per Andersen ◽  
F. Lindeløv ◽  
Terje Østvold ◽  
Alf Bjørseth ◽  
...  
Keyword(s):  
Activation Parameters ◽  
Free Base ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy

Kinetics in Solution

2008 ◽  
Author(s):  
José A. Martinho Simões ◽  
Manuel Minas da Piedade
Keyword(s):  
Analytical Method ◽  
Activation Parameters ◽  
Analytical Techniques ◽  
Frequency Factor ◽  
Nonequilibrium Kinetics ◽  
Entropy Of Activation ◽  
Concentration Changes ◽  
Enthalpy And Entropy ◽  
Reaction In Solution

The main equations used to extract thermochemical data from rate constants of reactions in solution were presented in section 3.2. Here, we illustrate the application of those equations with several examples quoted from the literature. First, however, recall that the rate constant for any elementary reaction in solution, defined in terms of concentrations, is related to the activation parameters through equations 15.1 or 15.2. Equation 15.1 yields the enthalpy and the entropy of activation respectively from the slope and the intercept of a ln(k/T) versus 1/T plot (an Eyring plot). Equation 15.2 leads to the Arrhenius activation energy and the frequency factor, respectively, from the slope and the intercept of a ln k versus 1/T plot (an Arrhenius plot). All the parameters refer to the mean temperature of the plot, and Δ‡Ho is related to Ea by equation 15.3. Finally, recall that if the activation parameters are available for the forward (subscript 1) and the reverse (subscript −1) reaction, the enthalpy of this reaction is calculated by equation 15.4. In the preceding chapter on equilibrium in solution, it was pointed out that any analytical method suitable for determining equilibrium compositions of a reaction mixture at several temperatures can be used to obtain the enthalpy and entropy of that reaction. A similar statement can be made here: Any analytical method suitable for monitoring concentration changes with time at several temperatures can be used to derive the activation parameters of a reaction. Therefore, the analytical techniques used in equilibrium experiments are also applied in nonequilibrium (kinetics) studies. However, in this case, the choice of the analytical method will have an additional and important restriction, for it must consider the reaction rate. An instrumental technique suitable for determining the concentration of a given species under equilibrium conditions may be inappropriate for determining a fast concentration change of the same species.

Studies on the decomposition of tetra-alkylammonium salts in solution. Part I. Phenylbenzylmethylallylammonium iodide

1968 ◽  
Vol 46 (8) ◽  
pp. 1215-1220 ◽  
Author(s):  
K. T. Leffek ◽  
F. H.-C. Tsao
Keyword(s):  
Reaction Kinetics ◽  
Isotope Effect ◽  
Optical Activity ◽  
Chloroform Solution ◽  
Activation Parameters ◽  
Deuterium Isotope Effect ◽  
Alkylammonium Salts ◽  
Triple Ion

The loss of optical activity from phenylbenzylmethylallylammonium iodide in chloroform solution has been found to be entirely due to decomposition; racemization as such does not take place. The products are benzyl iodide and allylmethylaniline. A mechanism involving decomposition via a triple ion is deduced from the reaction kinetics. The activation parameters (ΔH≠ and ΔS≠) and a secondary deuterium isotope effect are reported.

Studies on the kinetics of racemization of 2,4-disubstituted-5(4H)-oxazolones

1988 ◽  
Vol 66 (10) ◽  
pp. 2540-2544 ◽  
Author(s):  
Marek Slebioda ◽  
Marc A. St-Amand ◽  
Francis M. F. Chen ◽  
N. Leo Benoiton
Keyword(s):  
Nitrogen Atom ◽  
Tertiary Amine ◽  
Thermodynamic Data ◽  
Activation Parameters ◽  
Steric Effects ◽  
Tertiary Amines ◽  
Electronic Effects ◽  
Catalyzed Reactions ◽  
Kinetics Of ◽  
Benzyl Substituent

The kinetics of racemization of 2,4-disubstituted-5(4H)-oxazolones obtained from N-acetyl, N-benzoyl, and N-benzyloxycarbonylglycyl-L-leucine, -valine, and -phenylalanine have been studied in several solvents alone and in the presence of tertiary amines. The influence of the nature of the substituents on the rate of the reaction has been evaluated, and the values of the activation parameters ΔH≠ and ΔS≠ for the base-catalyzed reactions have been determined. The racemization process is governed by electronic effects of the C(2)-substituents and steric effects of the C(4)-substituents of the oxazolones. The thermodynamic data suggest that the 2-substituted-4-benzyl-5(4H)-oxazolones racemize more readily than the 4-alkyl analogues (alkyl ≠ benzyl) because of the unique conformation assumed by the benzyl substituent. The rate of the base-catalyzed reaction depends on the extent of hindrance about the nitrogen atom of the tertiary amine as well as on its basicity. The data suggest that the relative rates of racemization of oxazolones are not a true reflection of the relative tendencies to racemize of the pertinent residues during couplings of the parent acids.

scholarly journals Poly(N-isopropylacrylamide-co-methacrylic acid) microgel stabilized copper nanoparticles for catalytic reduction of nitrobenzene

2015 ◽  
Vol 33 (3) ◽  
pp. 627-634 ◽  
Author(s):  
Zahoor H. Farooqi ◽  
Zonarah Butt ◽  
Robina Begum ◽  
Shanza Rhauf Khan ◽  
Ahsan Sharif ◽  
...  
Keyword(s):  
Copper Nanoparticles ◽  
Methacrylic Acid ◽  
Catalytic Reduction ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Reducing Agent ◽  
Different Temperatures ◽  
Entropy Of Activation ◽  
Micro Reactors

Abstract Poly(N-isopropylacrylamide-co-methacrylic acid) microgels [p(NIPAM-co-MAAc)] were synthesized by precipitation polymerization of N-isopropylacrylamide and methacrylic acid in aqueous medium. These microgels were characterized by dynamic light scattering and Fourier transform infrared spectroscopy. These microgels were used as micro-reactors for in situ synthesis of copper nanoparticles using sodium borohydride (NaBH4) as reducing agent. The hybrid microgels were used as catalysts for the reduction of nitrobenzene in aqueous media. The reaction was performed with different concentrations of cat­alyst and reducing agent. A linear relationship was found between apparent rate constant (kapp) and amount of catalyst. When the amount of catalyst was increased from 0.13 to 0.76 mg/mL then kapp was increased from 0.03 to 0.14 min-1. Activation parameters were also determined by performing reaction at two different temperatures. The catalytic process has been discussed in terms of energy of activation, enthalpy of activation and entropy of activation. The synthesized particles were found to be stable even after 14 weeks and showed catalytic activity for the reduction of nitrobenzene.

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