Terms in Kinetic Models for Nonelementary Reactions

The types of intermediates we may postulate are suggested by the chemistry
of the materials. These may be grouped as follows.


Free Radical
Free atoms or larger fragments of stable molecules that contain one or more unpaired electrons are called free radicals.The unpaired electron is designated by a dot in the chemical symbol for the substance. Some free
radicals are relatively stable, such as triphenylmethyl


Ions and Polar Substances

Electrically charged atoms, molecules, or fragments of molecules. such as
N3-, Na+, OH-, 
called ions. These may act as active intermediates in reactions.


Transition Complexes.

The numerous collisions between reactant molecules result in a wide distribution of energies among the individual molecules. This can result in strained bonds, unstable forms of molecules, or unstable association
of molecules which can then either decompose to give products, or by further collisions return to molecules in the normal state. Such unstable forms are called transition complexes. Postulated reaction schemes involving these four kinds of intermediates can be of two types.
Nonchain Reactions.
Chain Reactions.






By Rajendra