Chemical reaction with a single step and transition state
An elementary reaction is a chemical reaction in which one or more chemical species react directly to form products in a single reaction step and with a single transition state. In practice, a reaction is assumed to be elementary if no reaction intermediates have been detected or need to be postulated to describe the reaction on a molecular scale.[1] An apparently elementary reaction may be in fact a stepwise reaction, i.e. a complicated sequence of chemical reactions, with reaction intermediates of variable lifetimes.
In a unimolecular elementary reaction, a molecule A dissociates or isomerises to form the products(s)
At constant temperature, the rate of such a reaction is proportional to the concentration of the species A
In a bimolecular elementary reaction, two atoms, molecules, ions or radicals, A and B, react together to form the product(s)
The rate of such a reaction, at constant temperature, is proportional to the product of the concentrations of the species A and B
The rate expression for an elementary bimolecular reaction is sometimes referred to as the law of mass action as it was first proposed by Guldberg and Waage in 1864. An example of this type of reaction is a cycloaddition reaction.
This rate expression can be derived from first principles by using collision theory for ideal gases. For the case of dilute fluids equivalent results have been obtained from simple probabilistic arguments.[2]
According to collision theory the probability of three chemical species reacting simultaneously with each other in a termolecular elementary reaction is negligible. Hence such termolecular reactions are commonly referred as non-elementary reactions and can be broken down into a more fundamental set of bimolecular reactions,[3][4] in agreement with the law of mass action. It is not always possible to derive overall reaction schemes, but solutions based on rate equations are often possible in terms of steady-state or Michaelis-Menten approximations.
^IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "elementary reaction". doi:10.1351/goldbook.E02035
^Gillespie, Daniel T. (2009-10-28). "A diffusional bimolecular propensity function". The Journal of Chemical Physics. 131 (16). doi:10.1063/1.3253798. ISSN 0021-9606. PMC 2780463. PMID 19894929.
^"Bimolecular routes to cubic autocatalysis - American Chemical Society - PDF Free Download". datapdf.com. Retrieved 2023-09-18.
^Aris, R.; Gray, P.; Scott, S. K. (1988-01-01). "Modelling cubic autocatalysis by successive bimolecular steps". Chemical Engineering Science. 43 (2): 207–211. doi:10.1016/0009-2509(88)85032-2. ISSN 0009-2509.
and 29 Related for: Elementary reaction information
An elementaryreaction is a chemical reaction in which one or more chemical species react directly to form products in a single reaction step and with...
different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementaryreactions, and the information on the...
react in an elementary (single-step) reaction and is equal to the sum of stoichiometric coefficients of reactants in the elementaryreaction with effective...
molecules. When so defined, for an elementary and irreversible reaction, v is the rate of successful chemical reaction events leading to the product. The...
consecutive elementaryreactions. In a stepwise reaction, not all bonds are broken and formed at the same time. Hence, intermediates appear in the reaction pathway...
A reaction step of a chemical reaction is defined as: "An elementaryreaction, constituting one of the stages of a stepwise reaction in which a reaction...
called partial orders of reaction and their sum is the overall order of reaction. In a dilute solution, an elementaryreaction (one having a single step...
decomposed into elementary processes (collisions, or steps, or elementaryreactions). It states that at equilibrium, each elementary process is in equilibrium...
the reaction rate to temperature. There are two objections to associating this activation energy with the threshold barrier for an elementaryreaction. First...
In chemistry, a reaction mechanism is the step by step sequence of elementaryreactions by which overall chemical reaction occurs. A chemical mechanism...
sequence of a stepwise chemical reaction. It is formed as the reaction product of an elementary step, from the reactants and/or preceding intermediates, but...
an elementary treatment that gives the quantitative basis of the relationship between the activation energy and the reaction rate at which a reaction proceeds...
the composition of a reaction mixture at equilibrium and 2) the kinetic aspect concerning the rate equations for elementaryreactions. Both aspects stem...
the titration is done with an automated Karl Fischer titrator. The elementaryreaction responsible for water quantification in the Karl Fischer titration...
enable the reaction at lower temperatures. This effect can be illustrated with an energy profile diagram. In the catalyzed elementaryreaction, catalysts...
It is stable in the sense that an elementaryreaction forms the reactive intermediate and the elementaryreaction in the next step is needed to destroy...
{\displaystyle A+B\rightleftharpoons 2B} with the rate equations (for an elementaryreaction) d d t [ A ] = − k + [ A ] [ B ] + k − [ B ] 2 {\displaystyle {d...
In electrochemistry, an electrochemical reaction mechanism is the step-by-step sequence of elementary steps, involving at least one outer-sphere electron...
the Arrhenius equation is a formula for the temperature dependence of reaction rates. The equation was proposed by Svante Arrhenius in 1889, based on...
Laminar flow reactors are often used to study an isolated elementaryreaction or multi-step reaction mechanism. Laminar flow reactors employ the characteristics...
of concentration), first order reactions, and second order reactions, and can be derived for others. Elementaryreactions follow the law of mass action...
the field of physical chemistry, a nonthermal surface reaction refers to an elementaryreaction between a thermally accommodated adsorbed surface species...
The December 14, 2012, Sandy Hook Elementary School shooting—in which a gunman shot and killed his mother at home, 20 students, 6 teachers, then himself—received...
chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive...
enzyme-catalysed chemical reactions. In enzyme kinetics, the reaction rate is measured and the effects of varying the conditions of the reaction are investigated...
B and the backward reaction in which B is converted into A. If both reactions are elementaryreactions, then the rate of reaction is given by d [ A ]...
in a reaction.[citation needed] Chemical reactions, as macroscopic unit operations, consist of simply a very large number of elementaryreactions, where...
{\text{B}}]=k[A][B]} unit mol⋅dm−3⋅s−1. Consider the bimolecular elementaryreaction: A + B → C In collision theory it is considered that two particles...
Global Information
![{\displaystyle {\frac {d[{\mbox{A}}]}{dt}}=-k[{\mbox{A}}].}](https://wikimedia.org/api/rest_v1/media/math/render/svg/dd60e0eed0d75c439483d4df73e4dfe1cb25def2)
![{\displaystyle {\frac {d[{\mbox{A}}]}{dt}}={\frac {d[{\mbox{B}}]}{dt}}=-k[{\mbox{A}}][{\mbox{B}}].}](https://wikimedia.org/api/rest_v1/media/math/render/svg/f53691c918b011c6bcf181176343ca7195d383c9)