Reactive intermediate
In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these compounds be isolated and stored, e.g. low temperatures, matrix isolation. When their existence is indicated, reactive intermediates can help explain how a chemical reaction takes place.[1][2][3][4]
Most chemical reactions take more than one
spectroscopic methods. It is stable in the sense that an elementary reaction
forms the reactive intermediate and the elementary reaction in the next step is needed to destroy it.
When a reactive intermediate is not observable, its existence must be
inferred through experimentation. This usually involves changing reaction conditions such as temperature or concentration and applying the techniques of chemical kinetics, chemical thermodynamics, or spectroscopy. Reactive intermediates based on carbon are radicals, carbenes, carbocations, carbanions, arynes, and carbynes
.
Common features
Reactive intermediates have several features in common:
- low concentration with respect to reaction substrate and final reaction product
- with the exception of carbanions, these intermediates do not obey the lewis octet rule, hence the high reactivity
- often generated on chemical decomposition of a chemical compound
- it is often possible to prove the existence of this species by spectroscopic means
- cage effectshave to be taken into account
- often stabilisation by resonance
- often difficult to distinguish from a transition state
- prove existence by means of chemical trapping
Carbon
-
Radical -
Carbene -
Carbocation -
Carbanion -
Carbyne -
Benzyne (an aryne)
Other reactive intermediates
- Carbenoid
- Ion-neutral complex
- Keto anions
- Nitrenes
- Oxocarbenium ions
- Phosphinidenes
- Phosphoryl nitride
- carbonyladdition reactions
See also
References
- ISBN 0-306-41198-9.
- ISBN 0-471-60180-2
- ISBN 9780306500268.
- ISBN 9780471721499.
Extranol links
Media related to Reactive intermediates at Wikimedia Commons
