Free radicals are formed by a process called homolytic fission. This is the
symmetric
breaking of a covalent bond, where each atom either side of the
bond gains one electron
from the pair. When the molecule has an unpaired
electron its stability decreases
making it more reactive. Radicals have an
odd number of electrons (often 7) and would
ideally have there stable
noble-gas configuration. They achieve this stable octet in
several ways. The
radicals are often short lived due to this unstable configuration
and
extremely reactive. A few free radicals do not fall into this category
and are
discussed under the heading "stable radicals" on the index page or by
clicking the link. Often these
reactions are hard to study due to the increased rate of
reaction and must be
carried out at very low concentrations. The kinetics of free
radical
reactions become more complicated and the reaction rate is a lot faster than
would be expected for other unimolecular reactions.
There are three steps that free radical reactions can be split into. These
are: