What is chain propagation and termination in free radical halogenation?
1 Answer
Propagation is the portion of the radical halogenation mechanism where most of the action occurs. The product usually is created at this step, although it might also be created in the termination steps.
Termination is merely when the reaction finishes, as suggested by the name; the reactants react in such a way that they become no longer reactive (i.e. they form the product, form an alkane, and reform the original dihalogen), hence finishing the reaction.
The parts of the whole mechanism are listed below, with some representative steps that fall under each category.
(Note that these are not supposed to illustrate a conservation of mass---it is assumed that it is the case. So don't count the atoms.)
-
Initiation
(Without this step, the reaction cannot proceed.) -
Propagation
(Here, the reactants form the necessary intermediates to form the product.) -
Termination
(Here, the reactants react such that they no longer become reactive, hence finishing the reaction.)
