Chain propagation (sometimes referred to as propagation) is a process in which a
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 comp ...
is continuously regenerated during the course of a
chemical chain reaction. For example, in the
chlorination of
methane, there is a two-step propagation cycle involving as chain carriers a chlorine atom and a
methyl radicalChain reaction
IUPAC Gold Book which are regenerated alternately:
:•Cl + CH4 → HCl + •CH3
:•CH3 + Cl2 → CH3Cl + •Cl
The two steps add to give the equation for the overall chain reaction:
:CH4 + Cl2 → CH3Cl + HCl.
Polymerization
In a chain-growth polymerization
Chain-growth polymerization (American English, AE) or chain-growth polymerisation (British English, BE) is a polymerization technique where Unsaturated compound, unsaturated monomer molecules add onto the active site on a growing polymer chain one ...
reaction, the reactive end-groups of a polymer chain react in each propagation step with a new monomer molecule transferring the reactive group to the last unit. Here the chain carrier is the polymer molecule with a reactive end-group, and at each step it is regenerated with the addition of one monomer unit:
:
External links
* IUPAC Gold Book definition
chain-propagating reaction
References
Chemical reactions
Polymer chemistry
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