20.3 : 自由基的形成：概述

Radicals can be made from spin-paired molecules or other radicals.

There are two possible routes from spin-paired compounds. First, homolysis, where one spin-paired molecule can form two radicals. Secondly, electron transfer or reduction.

Alternatively, there are three ways to create radicals from other radicals. Here, in general, one spin-paired molecule and one radical can interact to yield either a radical or a spin-paired molecule and a radical.

First is the substitution or abstraction method that involves the interaction of a radical with a spin-paired molecule to generate the corresponding spin-paired molecule and a radical.

Second is the addition method where a radical adds to an alkene to produce a new radical.

Last is the elimination method, which is the reverse of the addition method, and yields a new spin-paired molecule and a radical.