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In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical reaction occurs. [1]A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage of an overall chemical reaction.
The international pictogram for oxidizing chemicals. Dangerous goods label for oxidizing agents. An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "accepts"/"receives" an electron from a reducing agent (called the reductant, reducer, or electron donor).
The word strong is used since the strong interaction is the "strongest" of the four fundamental forces. At a distance of 10 −15 m, its strength is around 100 times that of the electromagnetic force , some 10 6 times as great as that of the weak force, and about 10 38 times that of gravitation .
Fluoroantimonic acid is the strongest superacid based on the measured value of its Hammett acidity function (H 0), which has been determined for various ratios of HF:SbF 5. The H 0 of HF is −15. [5] A solution of HF containing 1 mol % of SbF 5 is −20. The H 0 is −21 for 10 mol%. For > 50 mol % SbF 5, the H 0 is between −21 and −23.
The determining factor when both S N 2 and S N 1 reaction mechanisms are viable is the strength of the Nucleophile. Nuclephilicity and basicity are linked and the more nucleophilic a molecule becomes the greater said nucleophile's basicity. This increase in basicity causes problems for S N 2 reaction mechanisms when the solvent of choice is protic.
Following the addition elimination mechanism first a nucleophilic NH 2 − is added while a hydride (H −) is leaving. The reaction formally is a nucleophilic substitution of hydrogen S N H. Ciganek describes an example of an intramolecular Chichibabin reaction in which a nitrile group on a fused ring is the source of nitrogen in amination. [2]
In these reactions, the conjugate acid of the carbonyl group is a better electrophile than the neutral carbonyl group itself. Depending on the chemical species that act as the acid or base, catalytic mechanisms can be classified as either specific catalysis and general catalysis. Many enzymes operate by general catalysis.
At fuel-rich conditions, due to lack of oxygen, reaction 2 becomes weak, hence, a third reaction is included in the mechanism, also known as extended Zel'dovich mechanism (with all three reactions), [5] [6]