Reaction mechanism

Curved arrows describing electron shifts: electron pair shift (left) and one-electron shift (right).

A reaction mechanism describes the process from reactant to product of a mostly chemical reaction , whereby intermediate products and transition states are fully characterized. It must be consistent with the rate equation , stoichiometry, and the observations of stereochemistry . Conclusions about the electron movements can be indicated with curved arrows (↷).

In organic chemistry, most of the steps in a reaction mechanism can be assigned to known elementary reactions . In nuclear physics, the series of decays are built up from the various types of decay as elementary steps. Another elementary step is nuclear fusion .

The elucidation of a reaction mechanism is an inverse problem in which not only model parameters have to be determined, but the structure of the model is initially unknown. Here, change experiment and modeling from. The dependencies of the reaction rate (see reaction kinetics ) or the product spectrum (see chemical analysis ), for example on the temperature or the pH value, as well as (often spectroscopically ) short-lived intermediates are observed . In chemical reaction engineering , this can be referred to as a reaction network.

Many reaction mechanisms are named after their discoverers and are referred to as name reactions . The Baker-Venkataraman rearrangement consists of several organic elementary reactions, the Belousov-Zhabotinsky reaction mainly consists of inorganic reactions and the Bethe-Weizsäcker cycle consists of nuclear fusions and decays.

literature

• Peter Sykes : How do chemical reactions work? Response mechanisms for beginners . 2nd edition, Wiley-VCH, Weinheim 2001, ISBN 978-3-527-30305-2 .
• Siegfried Hauptmann : Reaction and Mechanism in Organic Synthesis , BG Teubner Verlag, Stuttgart, 1991, ISBN 3-519-03515-4 .
• Hermann Höver: reaction mechanisms of organic chemistry , Verlag Chemie, Weinheim, 1973, ISBN 3-527-25442-0 .
• Ulrich Lüning: Organic reactions , Spectrum Akademischer Verlag / Elsevier GmbH, Munich 2007, 2nd edition, ISBN 978-3-8274-1834-0 .
• Reinhard Brückner: Reaction Mechanisms , Springer Verlag, Berlin and Heidelberg 2007, corrected reprint of the 3rd edition, ISBN 978-3-8274-1579-0 .

Web links

Wiktionary: reaction mechanism  - explanations of meanings, word origins, synonyms, translations

Wikibooks: Reaction Mechanisms in Organic Chemistry  - Learning and Teaching Materials

• Video: How do we describe the kinetics of more complex reactions . Jakob Günter Lauth (SciFox) 2019, made available by the Technical Information Library (TIB), doi : 10.5446 / 40357 .

Individual evidence

1. ↑ Entry on reaction mechanism . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.M03804 .