On the problem of empirical characteristics of a medium and their mutual relations

1983 ◽  
Vol 48 (5) ◽  
pp. 1237-1240 ◽  
Author(s):  
Vojtěch Bekárek ◽  
Marie Stolařová
Keyword(s):  
Free Energy ◽  
Refractive Index ◽  
Solvent Effects ◽  
Hyperfine Splitting ◽  
Ion Pairs ◽  
Life Time ◽  
Reaction Rates ◽  
Epr Spectra ◽  
Solvent Parameters ◽  
Mutual Relations

New parameters of polarity, acidity, and basicity of a medium, which are more suitable to characterize nonspectral solvent effects, were derived by dividing the Taft-Kamlet solvent parameters π*, α, and β by a function of the refractive index n, f(n) = (n2 - 1)/(2n2 + 1). The new parameters were used in evaluating the effect of the medium on reaction rates, equilibria, solubilities, hyperfine splitting constants in EPR spectra, fluorescence life time, free energy of dissolution of ions and ion pairs, and on the Snyder solvent factors of the elution strength in chromatography.

A contribution to evaluation of influence of medium in electronic and infrared spectroscopy

1982 ◽  
Vol 47 (4) ◽  
pp. 1060-1068 ◽  
Author(s):  
Vojtěch Bekárek ◽  
Jan Juřina
Keyword(s):  
Refractive Index ◽  
Infrared Spectroscopy ◽  
Correlation Coefficient ◽  
Solvent Effects ◽  
Electronic Spectra ◽  
Relative Permittivity ◽  
Solvent Parameters

Dependence of ET(30) of solvent parameters on relative permittivity (ε) and refractive index (n) of solvent has been found for forty solvents in the form ET(30)=29.87 + 72.03 (ε - 1/(2ε + 1)-29.16(ε - 1) (n 2 - 1)/(2ε + 1) (2n2 + 1), the correlation coefficient being 0.958. Relation has been discussed between ET(30) and π solvent parameters and significance of the term (ε - 1). (n2 - 1)/(2ε + 1) (2n2 + 1) has been tested for evaluation of solvent effects in electronic spectra.>

Kinetic Solvent Effects in Organic Reactions

2017 ◽  
Author(s):  
Belinda Slakman ◽  
Richard West
Keyword(s):  
Solvent Effect ◽  
Reaction Kinetics ◽  
Computational Methods ◽  
High Throughput ◽  
Kinetic Modeling ◽  
Solvent Effects ◽  
Reaction Rates ◽  
Prior Work ◽  
Solvent Phase ◽  
High Throughput Manner

<div> <div> <div> <p>This article reviews prior work studying reaction kinetics in solution, with the goal of using this information to improve detailed kinetic modeling in the solvent phase. Both experimental and computational methods for calculating reaction rates in liquids are reviewed. Previous studies, which used such methods to determine solvent effects, are then analyzed based on reaction family. Many of these studies correlate kinetic solvent effect with one or more solvent parameters or properties of reacting species, but it is not always possible, and investigations are usually done on too few reactions and solvents to truly generalize. From these studies, we present suggestions on how best to use data to generalize solvent effects for many different reaction types in a high throughput manner. </p> </div> </div> </div>

Kinetics of Ion-Pair Effect of Aquation of Bromopentaammine Cobalt(III) Complex in Different Dicarboxylate Media

2011 ◽  
Vol 324 ◽  
pp. 166-169 ◽  
Author(s):  
Farah Zeitouni ◽  
Gehan El-Subruiti ◽  
Ghassan Younes ◽  
Mohammad Amira
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Compensation Effect ◽  
Ion Pairing ◽  
Reaction Rates ◽  
Ion Pair ◽  
Free Energy Of Activation ◽  
Different Types ◽  
Different Temperatures ◽  
Kinetics Of

The rate of aquation of bromopentaammine cobalt(III) ion in the presence of different types of dicarboxylate solutions containing tert-butanol (40% V/V) have been measured spectrophotometrically at different temperatures (30-600°C) in the light of the effects of ion-pairing on reaction rates and mechanism. The thermodynamic and extrathermodynamic parameters of activation have been calculated and discussed in terms of solvent effect on the ion-pair aquation reaction. The free energy of activation ∆Gip* is more or less linearly varied among the studied dicarboxylate ion-pairing ligands indicating the presence of compensation effect between ∆Hip* and ∆Sip*. Comparing the kip values with respect of different buffers at 40% of ter-butanol is introduced.

Solvent effects on the nitrogen and β-hydrogen hyperfine splitting constants of aminoxyl radicals obtained in spin trapping experiments

1982 ◽  
Vol 60 (21) ◽  
pp. 2725-2733 ◽  
Author(s):  
Edward G. Janzen ◽  
Gregory A. Coulter ◽  
Uwe M. Oehler ◽  
John P. Bergsma
Keyword(s):  
Linear Relationship ◽  
Solvent Effects ◽  
Hyperfine Splitting ◽  
Spin Trapping ◽  
Tert Butyl ◽  
Aminoxyl Radicals ◽  
Structural Significance

The nitrogen and β-hydrogen hyperfine splitting constants (hfsc) for phenyl, 4-nitrophenyl, 4-pyridyl, benzoyl, and trichloromethyl spin adducts of α-phenyl tert-butyl nitrone (PBN) as well as for the tert-butoxyl adduct of 5,5-dimethylpyrroline-N-oxide (DMPO) have been obtained as a function of solvent (30 solvents). A useful linear relationship between the β-H hfsc and the N-hfsc of each aminoxyl is found except for the benzoyl adduct of PBN. Some speculations regarding the structural significance of these correlations is presented.

scholarly journals The comparative study of linear solvatation energy relationship for the reactivity of pyridine carboxylic acids with diazodiphenylmethane in protic and aprotic solvents

2012 ◽  
Vol 77 (10) ◽  
pp. 1311-1338 ◽  
Author(s):  
Sasa Drmanic ◽  
Jasmina Nikolic ◽  
Aleksandar Marinkovic ◽  
Bratislav Jovanovic
Keyword(s):  
Solvent Effects ◽  
Kinetic Data ◽  
Aprotic Solvent ◽  
Isonicotinic Acid ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Reaction Rates ◽  
Aprotic Solvents ◽  
Pyridine Carboxylic ◽  
The Comparative Study

Protic and aprotic solvent effects on the reactivity of picolinic, nicotinic and isonicotinic acid, as well as of some substituted nicotinic acids with diazodiphenylmethane (DDM) were investigated. In order to explain the kinetic results through solvent effects, the second-order rate constants for the reaction of the examined acids with DDM were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of the multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and the transition state. The signs of the equation coefficients support the already known reaction mechanism. The solvatation models for all the investigated acids are suggested and related to their specific structure.

Experimental evidence for the need of thermodynamic considerations in modelling of anaerobic environmental bioprocesses

1997 ◽  
Vol 36 (10) ◽  
pp. 109-115 ◽  
Author(s):  
Choon-Yee Hoh ◽  
Ralf Cord-Ruwisch
Keyword(s):  
Free Energy ◽  
Experimental Evidence ◽  
Positive Reaction ◽  
Rate Equation ◽  
Dynamic Equilibrium ◽  
Reaction Rates ◽  
Product Inhibition ◽  
Experimental Results ◽  
Biological Processes ◽  
Laws Of Thermodynamics

For modeling of biological processes that operate close to the dynamic equilibrium (eg. anaerobic processes), it is critical to prevent the prediction of positive reaction rates when the reaction has already reached dynamic equilibrium. Traditional Michaelis-Menten based models were found to violate the laws of thermodynamics as they predicted positive reaction rates for reactions that were endergonic due to high endproduct concentrations. The inclusion of empirical “product inhibition factors” as suggested by previous work could not prevent this problem. This paper compares the predictions of the Michaelis-Menten Model (with and without product inhibition factors) and the Equilibrium Based Model (which has a thermodynamic term introduced into its rate equation) with experimental results of reactions in anaerobic bacterial environments. In contrast to the Michaelis-Menten based models that used traditional inhibition factors, the Equilibrium Based Model correctly predicted the nature and the degree of inhibition due to endproduct accumulation. Moreover, this model also correctly predicted when reaction rates must be zero due to the free energy change of the conversion reaction being zero. With these added advantages, the Equilibrium Based Model thus seemed to provide a scientifically correct and more realistic basis for a variety of models that describe anaerobic biosystems.

Solvent effects on the reactivity of solvated electrons with ammonium and nitrate ions in 1-butanol–water solvents

1993 ◽  
Vol 71 (9) ◽  
pp. 1303-1310 ◽  
Author(s):  
Ruzhong Chen ◽  
Gordon R. Freeman
Keyword(s):  
Solvent Effects ◽  
Pure Water ◽  
Reaction Rates ◽  
Dielectric Relaxation Time ◽  
Unusual Behavior ◽  
Solvated Electrons ◽  
Water Solvent ◽  
Electrical Conductances ◽  
Average Size ◽  
Effective Reaction

Values of the rate constants, k2 (106 m3 mol−1 s−1), of solvated electrons,[Formula: see text] with several related salts, in pure water and pure 1-butanol solvents at 298 K are, respectively, as follows: LiNO3, 9.2, 0.19; NH4NO3, 10, 8.3; NH4ClO4, 1.5 × 10−3, 12 in 20 mol% water; LiClO4, 1.0 × 10−4, < 1.0 × 10−4. The value of [Formula: see text] in water solvent is 48 times larger than that in 1-butanol solvent, whereas [Formula: see text] in water is 10−4 times smaller than the value in 1-butanol. This enormous reversal of solvent effects on [Formula: see text] reaction rates is the first observed for ionic reactants. The solvent participates chemically in the [Formula: see text] reaction, and the overall rate constant increases with increasing viscosity and dielectric relaxation time. This unusual behavior is attributed to a greatly increased probability of reaction of an encounter pair with increasing duration of the encounter. Effective reaction radii κRr for [Formula: see text] and [Formula: see text] were estimated with the aid of measured electrical conductances of the salt solutions in all the solvents. Values of κRr are (2–7) × 10−10 m, except for NH4,s+ in 100 and 99 mol% water, which are 2.6 and 2.7 × 10−14 m, respectively. The effective radii of the ions for mutual diffusion increase with increasing butanol content of the solvent, from ~50 pm in water to ~150 pm in 1-butanol, due to the increasing average size of the molecules that solvate the ions.

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