Kinetics Solvent Effect and Mechanism of Hydrolysis of Ethyl Caprylate Ester in Aqueous Organic Solvent Media

2021 ◽  
pp. 445-447
Author(s):  
A. K. Singh
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Organic Solvent ◽  
Reaction Kinetic ◽  
Specific Rate ◽  
Organic Solvent Media ◽  
Rate Of Reaction ◽  
Specific Rate Constant ◽  
Mechanism Of Hydrolysis ◽  
Hydrolysis Of

The specific rate constant of ethyl caprylate in alkali catalised hydrolysis in water-acetone mixture covering range of 30 to 70% (v/v) of acetone has been determined at temperature 20 to 400c. The rate of reaction decreases with increase in percentage of Acetone from 30 to 70% (v/v). The observed Activation energy decreases progressively with increase in acetone content of the medium. The effect of molar concentration of water and Dielectric constant on the reaction kinetic has also been studied. The thermodynamic parameters (DG*, DH* and DS*) has been determined which showed strong dependency on solvent composition.

A Raman Spectral Study of the Kinetics of Hydrolysis of Acetonitrile Catalyzed by Hg(II)

1975 ◽  
Vol 53 (3) ◽  
pp. 427-436 ◽  
Author(s):  
Yu-Keung Sze ◽  
Donald E. Irish
Keyword(s):  
Time Span ◽  
Water Molecules ◽  
Specific Rate ◽  
Ammine Complexes ◽  
Kinetics Of Hydrolysis ◽  
Specific Rate Constant ◽  
Rate Of Hydrolysis ◽  
Raman Spectral ◽  
Kinetics Of ◽  
Hydrolysis Of

Raman spectroscopy has been employed to follow the relatively slow rate of hydrolysis of acetonitrile, catalyzed by mercury(II). Raman lines at 2275 and 2305 cm−1 are characteristic of CH3CN bound to Hg2+, and are distinct from lines of bulk solvent. The intensities of these new lines decrease with time. From the intensities, concentrations of bound acetonitrile, [CH3CN]B were calculated for a time span of 400 min. The data fit a second order rate law: Rate = k[CH3CN]B[H2O]. The specific rate constant, k, obtained from four sets of data for the system Hg(ClO4)2–CH3CN–H2O equals 1.05 ± 0.06 × 10−4 mol−1 1 min−1 at 25 °C. The energy of activation is 18.9 kcal mol−1. In the proposed mechanism water molecules attack acetonitrile molecules which are bound to Hg2+ and form a mercury(II)–acetamide complex. Raman lines characteristic of this species are observed. This species slowly converts to mercury(II) ammine complexes and acetic acid. Anions which coordinate with Hg2+ more strongly than CH3CN, such as nitrate or acetate, slow or prevent the hydrolysis reaction.

Optimization of Chlorophyllase-catalyzed Hydrolysis of Chlorophyll in Monophasic Organic Solvent Media

2007 ◽  
Vol 142 (3) ◽  
pp. 263-275 ◽  
Author(s):  
Paula Arriagada-Strodthoff ◽  
Salwa Karboune ◽  
Ronald J. Neufeld ◽  
Selim Kermasha
Keyword(s):  
Organic Solvent ◽  
Organic Solvent Media ◽  
Hydrolysis Of

Phosphorylation of Ca2+-ATPase by Inorganic Phosphate in Water-Organic Solvent Media: Dielectric Constant and Solvent Hydrophobicity Contribution

1982 ◽  
Vol 37 (5-6) ◽  
pp. 527-531 ◽  
Author(s):  
Angela de Souza Otero ◽  
Leopoldo de Meis
Keyword(s):  
Dielectric Constant ◽  
Organic Solvent ◽  
Inorganic Phosphate ◽  
Mixed Solvents ◽  
Solvent Mixtures ◽  
Pronounced Increase ◽  
Calcium Gradient ◽  
Organic Solvent Media ◽  
Water Solvent ◽  
Reaction In Water

Abstract The effect of organic solvents on the phosphorylation of the Ca2+-dependent ATPase of sarcoplasmic reticulum by inorganic phosphate in the absence of a calcium gradient was investigated. Kinetic analysis of the reaction in water and water-organic solvent media according to a bireactant scheme shows no correlation between changes in kinetic parameters and the dieletric constant of the mixed solvents. The pronounced increase in equilibrium levels of phosphoenzyme in water-solvent mixtures is attributed to changes in the water activity of the medium.

Kinetic Study of the Acid Hydrolysis of Ethyl Hydrogen Succinate in Binary Solvent Mixtures

1978 ◽  
Vol 33 (12) ◽  
pp. 1479-1483 ◽  
Author(s):  
Fayez Y. Khalil ◽  
M. T. Hanna
Keyword(s):  
Organic Solvent ◽  
Free Water ◽  
Solvent Composition ◽  
Initial Increase ◽  
Binary Solvent ◽  
Specific Rate ◽  
Water Medium ◽  
Solvent Mixtures ◽  
Acetone Water ◽  
Hydrolysis Of

Abstract The specific rate constants for the acid-catalysed hydrolysis of ethyl hydrogen succinate in water and in a series of acetone-water and dioxane-water mixtures were determined at 30-45 °C. The solvent composition covered the range 0-90% by weight of the organic solvent. The rate was found to decrease to a minimum at about 80% of the organic solvent then to increase again with successive addition of the latter. In dioxane-water medium a slight initial increase in rate on the first addition of dioxane to water was observed and attributed to an increase in the number of "free" water molecules. The activation energy showed only slight dependence on solvent composition. The radius of the activated complex was calculated in the two media. The thermodynamic parameters were evaluated and discussed in terms of solvent composition. The reaction proved to be essentially an ion-dipole rather than an ion-ion interaction. A comparative discussion of the specific solvent effects of the two solvent systems under consideration is presented, based on the respective bond energies as given by the heats of mixing of the solvent components.

Kinetics of Acid-Catalysed Hydrolysis of Diethylsuccinate in Dioxane-Water Mixtures

1982 ◽  
Vol 37 (4) ◽  
pp. 390-394
Author(s):  
Fayez Y . Khalil ◽  
F. M. Abdel-Halim ◽  
Adel N. Asaad
Keyword(s):  
Dielectric Constant ◽  
Thermodynamic Parameters ◽  
Rate Constants ◽  
Solvent Composition ◽  
Specific Rate ◽  
Molecular Dipole ◽  
First Order ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Activated Complex

Abstract The specific rate constants k1 and k2 of the consecutive first-order acid-catalysed hydrolysis steps of diethylsuccinate in dioxane-water mixtures covering the range 0-95% (w/w) of dioxane are determined at 25-55 °C. As the concentration of dioxane increases, the rate of the reaction decreases to a minimum at about 90% (w/w) dioxane, after which it increases again. The ratio k1/k2 was found to be almost constant at the value 2.0. The activation energies of the reaction are independent of solvent composition. Available electrostatic theories regarding the effect of the dielectric constant on the rate are presented, from which the reaction is shown to be an ion-molecular dipole type of interaction. The thermodynamic parameters and the radii of the activated complex at different solvent compositions are calculated and discussed.

Kinetic and Mechanistic Studies of the Acid-Catalysed Hydrolysis of Ditert.-butyl Malonate in Dioxane-Water Media

1986 ◽  
Vol 41 (11) ◽  
pp. 1330-1334
Author(s):  
Fayez Y. Khalil ◽  
Morcos T. Hanna ◽  
Adel N. Asaad
Keyword(s):  
Dielectric Constant ◽  
Organic Solvent ◽  
Rate Constants ◽  
Maximum Concentration ◽  
Steric Effects ◽  
Kinetic Investigation ◽  
Mechanistic Studies ◽  
Water Media ◽  
Hydrolysis Of

A kinetic investigation of the consecutive acid-catalysed hydrolysis of ditert.-butyl malonate in dioxane-water mixtures is given. The rate constants of the first and second hydrolysis steps decrease by addition of the organic solvent, and both steps proceed concurrently by AA11 and AAc2 mechanisms. The kinetic ratio kI/kII depends on the solvent composition. The results are compared with those obtained previously for ditert.-butyl succinate in many aspects such as rate, percentage AA11 fission and the role of the inductive as well as steric effects. The maximum concentration of the intermediate, halfester, decreases with decrease in the ionising power of the solvent and has nearly the same value for malonate and succinate in isocomposition media. The effect of the dielectric constant on the rate constant and the activation thermodynamic parameters are discussed.

scholarly journals Tagasaste, leucaena and paulownia: three industrial crops for energy and hemicelluloses production

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Alberto Palma ◽  
Javier Mauricio Loaiza ◽  
Manuel J. Díaz ◽  
Juan Carlos García ◽  
Inmaculada Giráldez ◽  
...  
Keyword(s):  
Activation Energy ◽  
Acid Hydrolysis ◽  
Energy Production ◽  
Combustion Process ◽  
Operating Conditions ◽  
Raw Material ◽  
Energy Of Combustion ◽  
Increasing Temperature ◽  
Hydrolysis Of ◽  
Chamaecytisus Proliferus

Abstract Background Burning fast-growing trees for energy production can be an effective alternative to coal combustion. Thus, lignocellulosic material, which can be used to obtain chemicals with a high added value, is highly abundant, easily renewed and usually inexpensive. In this work, hemicellulose extraction by acid hydrolysis of plant biomass from three different crops (Chamaecytisus proliferus, Leucaena diversifolia and Paulownia trihybrid) was modelled and the resulting solid residues were used for energy production. Results The influence of the nature of the lignocellulosic raw material and the operating conditions used to extract the hemicellulose fraction on the heat capacity and activation energy of the subsequent combustion process was examined. The heat power and the activation energy of the combustion process were found to depend markedly on the hemicellulose content of the raw material. Thus, a low content in hemicelluloses resulted in a lower increased energy yield after acid hydrolysis stage. The process was also influenced by the operating conditions of the acid hydrolysis treatment, which increased the gross calorific value (GCV) of the solid residue by 0.6–9.7% relative to the starting material. In addition, the activation energy of combustion of the acid hydrolysis residues from Chamaecytisus proliferus (Tagasaste) and Paulownia trihybrid (Paulownia) was considerably lower than that for the starting materials, the difference increasing with increasing degree of conversion as well as with increasing temperature and acid concentration in the acid hydrolysis. The activation energy of combustion of the solid residues from acid hydrolysis of tagasaste and paulownia decreased markedly with increasing degree of conversion, and also with increasing temperature and acid concentration in the acid hydrolysis treatment. No similar trend was observed in Leucaena diversifolia (Leucaena) owing to its low content in hemicelluloses. Conclusions Acid hydrolysis of tagasaste, leucaena and paulownia provided a valorizable liquor containing a large amount of hemicelluloses and a solid residue with an increased heat power amenable to efficient valorization by combustion. There are many potential applications of the hemicelluloses-rich and lignin-rich fraction, for example as multi-components of bio-based feedstocks for 3D printing, for energy and other value-added chemicals.

Sign in / Sign up

Export Citation Format

Share Document