A chain-propagating reaction, or more simply a propagating reaction, is an elementary step in a
chain reaction in which one
chain carrier is converted into another. The conversion can be a
unimolecular reaction or a
bimolecular reaction with a reactant molecule.
Source:
PAC, 1996, 68, 149
(A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996))
on page 157