An analytical model for mechanochemical reaction kinetics

2021 ◽  
Author(s):  
Maria Carta ◽  
Francesco Delogu ◽  
Andrea Porcheddu
Keyword(s):  
Reaction Kinetics ◽  
Analytical Model ◽  
Chemical Reactions ◽  
Solvent Free ◽  
Mechanochemical Reaction ◽  
Synthetic Routes ◽  
Chemical Products

With its ability to enable solvent-free chemical reactions, mechanochemistry promises to open new and greener synthetic routes to chemical products of industrial interest. Its practical exploitation requires understanding the relationships...

Temperature Dependent Green Synthesis of 3-Carboxycoumarins and 3,4-unsubstituted Coumarins

2019 ◽  
Vol 16 (1) ◽  
pp. 130-135 ◽  
Author(s):  
Jack van Schijndel ◽  
Dennis Molendijk ◽  
Luiz Alberto Canalle ◽  
Erik Theodorus Rump ◽  
Jan Meuldijk
Keyword(s):  
Knoevenagel Condensation ◽  
Ammonium Bicarbonate ◽  
Solvent Free ◽  
Temperature Dependent ◽  
Step Procedure ◽  
Synthetic Routes ◽  
High Yields ◽  
Temperature Optima ◽  
Solvent Free Synthesis ◽  
Full Conversion

Aim and Objective: Because of the low abundance of 3,4-unsubstituted coumarins in plants combined with the complex purification process required, synthetic routes towards 3,4-unsubstituted coumarins are especially valuable. In the present work, we explore the possibilities of a solvent-free Green Knoevenagel condensation on various 2-hydroxybenzaldehyde derivatives and malonic acid without the use of toxic organocatalysts like pyridine and piperidine but only use ammonium bicarbonate as the catalyst. Materials and Methods: To investigate the scope of the Green Knoevenagel condensation for the synthesis of 3,4-unsubstituted coumarins, various 2-hydroxybenzaldehyde derivatives were screened as starting material in the optimized two-step procedure developed for 2-hydroxybenzaldehyde. </P><P> Results: This study shows that the intramolecular esterification and the decarboxylation are in competition, but show different temperature optima. In order to suppress premature decarboxylation and maximize the yield of coumarin, a two-step procedure was adopted. The reaction mixture containing ammonium bicarbonate is initially kept at 90ºC for 1 hour. After completion of the cyclization, the temperature of the reaction mixture is increased to 140ºC for 2 hours. Following this protocol, coumarin could be isolated with a yield of 95%. Conclusion: A two-step procedure for the solvent-free synthesis of several 3,4-unsubstituted coumarins was developed using ammonium bicarbonate, resulting in high yields of the desired products. Moreover, this procedure has a low E-factor and is, therefore an environmental friendly reaction in line with the principles of Green Chemistry. It was shown that by initially capping the temperature at 90ºC, premature decarboxylation can be suppressed. After full conversion to the intermediate 3-carboxycoumarin, the temperature can be increased to 140ºC finalizing the reaction. Ammonium bicarbonate was shown to catalyze both the Green Knoevenagel condensation and the decarboxylation step.

Normal approximations for distributions arising in the stochastic approach to chemical reaction kinetics

1981 ◽  
Vol 18 (01) ◽  
pp. 263-267 ◽  
Author(s):  
F. D. J. Dunstan ◽  
J. F. Reynolds
Keyword(s):  
Reaction Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Stochastic Approach ◽  
Algebraic Functions ◽  
Chemical Reaction Kinetics ◽  
Normal Approximations ◽  
Formal Solutions

Earlier stochastic analyses of chemical reactions have provided formal solutions which are unsuitable for most purposes in that they are expressed in terms of complex algebraic functions. Normal approximations are derived here for solutions to a variety of reactions. Using these, it is possible to investigate the level at which the classical deterministic solutions become inadequate. This is important in fields such as radioimmunoassay.

Determination of the Stress Distribution at the Interface Metal-Oxide: Numerical and Theoretical Considerations

2005 ◽  
Vol 237-240 ◽  
pp. 145-150 ◽  
Author(s):  
Sébastien Garruchet ◽  
A. Hasnaoui ◽  
Olivier Politano ◽  
Tony Montesin ◽  
J. Marcos Salazar ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Stress Distribution ◽  
Oxide Film ◽  
Metal Oxide ◽  
Reaction Kinetics ◽  
Analytical Model ◽  
Equilibrium Thermodynamics ◽  
Theoretical Considerations ◽  
Molecular Dynamics Results

In this paper we give a brief presentation of the approaches we have recently developed on the oxidation of metals. Firstly, we present an analytical model based on non-equilibrium thermodynamics to describe the reaction kinetics present during the oxidation of a metal. Secondly, we present the molecular dynamics results obtained with a code specially tailored to study the oxidation and growth of an oxide film of aluminium. Our simulations present an excellent agreement with experimental results.

scholarly journals The mechanochemical synthesis of quinazolin-4(3H)-ones by controlling the reactivity of IBX

2018 ◽  
Vol 14 ◽  
pp. 2396-2403 ◽  
Author(s):  
Md Toufique Alam ◽  
Saikat Maiti ◽  
Prasenjit Mal
Keyword(s):  
Chemical Reactions ◽  
Mechanochemical Synthesis ◽  
Exothermic Reaction ◽  
Amide Group ◽  
Solvent Free ◽  
Hypervalent Iodine ◽  
Maximum Contact

Performing any synthesis using several arylamines and hypervalent iodine(V) reagents by direct mixing is unrealistic because of the high exothermic reaction or explosion. Herein we demonstrate, when anilines were substituted with an amide group at the ortho-position, successful chemical reactions could be performed due to intramolecular control. At maximum contact of the reacting substances, i.e., under solvent-free mechanochemical conditions, 2-aminobenzamides, aryl-, alkylaldehydes and the iodine(V) reagent o-iodoxybenzoic acid (IBX) led to substituted quinazolin-4(3H)-one derivatives in fair yields.

Chemical Reaction Kinetics in Solution

2004 ◽  
Author(s):  
W. Ronald Fawcett
Keyword(s):  
Reaction Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Physical Property ◽  
Theoretical Description ◽  
Time Range ◽  
Chemical Changes ◽  
Elementary Reactions ◽  
Chemical Reaction Kinetics ◽  
Liquid Solutions

The kinetics of chemical reactions were first studied in liquid solutions. These experiments involved mixing two liquids and following the change in the concentration of a reactant or product with time. The concentration was monitored by removing a small sample of the solution and stopping the reaction, for example, by rapidly lowering the temperature, or by following a physical property of the system in situ, for example, its color. Although the experiments were initially limited to slow reactions, they established the basic laws governing the rate at which chemical changes occur. The variables considered included the concentrations of the reactants and of the products, the temperature, and the pressure. Thus, the reacting system was examined using the variables normally considered for a system at equilibrium. Most reactions were found to be complex, that is, to be made up of several elementary steps which involved one or two reactants. As the fundamental concepts of chemical kinetics developed, there was a strong interest in studying chemical reactions in the gas phase. At low pressures the reacting molecules in a gaseous solution are far from one another, and the theoretical description of equilibrium thermodynamic properties was well developed. Thus, the kinetic theory of gases and collision processes was applied first to construct a model for chemical reaction kinetics. This was followed by transition state theory and a more detailed understanding of elementary reactions on the basis of quantum mechanics. Eventually, these concepts were applied to reactions in liquid solutions with consideration of the role of the non-reacting medium, that is, the solvent. An important turning point in reaction kinetics was the development of experimental techniques for studying fast reactions in solution. The first of these was based on flow techniques and extended the time range over which chemical changes could be observed from a few seconds down to a few milliseconds. This was followed by the development of a variety of relaxation techniques, including the temperature jump, pressure jump, and electrical field jump methods. In this way, the time for experimental observation was extended below the nanosecond range.

Solvent-Free Polymorphism Control in a Covalent Mechanochemical Reaction

2011 ◽  
Vol 12 (1) ◽  
pp. 44-48 ◽  
Author(s):  
Dominik Cinčić ◽  
Ivana Brekalo ◽  
Branko Kaitner
Keyword(s):  
Solvent Free ◽  
Mechanochemical Reaction

Solvent-free iodine-promoted synthesis of 3,2′-pyrrolinyl spirooxindoles from alkylidene oxindoles and enamino esters under ball-milling conditions

2017 ◽  
Vol 53 (92) ◽  
pp. 12477-12480 ◽  
Author(s):  
Hui Xu ◽  
Hong-Wei Liu ◽  
Hao-Sheng Lin ◽  
Guan-Wu Wang
Keyword(s):  
Ball Milling ◽  
Solvent Free ◽  
Mechanochemical Reaction ◽  
Free Iodine

A solvent-free mechanochemical reaction of alkylidene oxindoles with enamino esters via an iodine-promoted tandem Michael/cyclization sequence has been developed to provide a variety of spirocyclic oxindoles in moderate to good yields with excellent diastereoselectivities.

An Analytical Model of Phase Changing Chemically Reacting Mixture Flows

2003 ◽  
Author(s):  
George S. Dulikravich ◽  
Marcelo J. Colac¸o
Keyword(s):  
Mathematical Model ◽  
Analytical Model ◽  
Chemical Reactions ◽  
Continuum Mechanics ◽  
Multiphase Flows ◽  
Phase Changes ◽  
Chemically Reacting

A complete and consistent mathematical model of multiphase flows allowing for chemical reactions and/or phase changes has been derived from basic continuum mechanics principles. Comparison of elements of this model with models published by other sources has been elaborated. A set of analytic relations linking mixture and fluid components has been derived. Conclusions about closure of the system have been drawn based on these derivations.

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