For 10 points, name this class of reactions which forms long chains of monomers.
Tromsdorff's "gel effect" explains the increase in the rate of these reactions due to increased viscosity. Under metal catalysis, these reactions occur via ligand association, then a stereospecific migratory insertion, though beta-hydride eliminations can generate undesired side products. That's the Cossee-Arlman mechanism. In the "living" form of these reactions, a narrow product distribution is made. A ring-opening metathesis example of them is catalyzed by Grubbs' catalyst. Branching can be reduced in these reactions by adding titanium and aluminum-based Ziegler-Natta catalysts. Ethylene adds to a double bond in a radical mechanism in an example of the chain-growth type of these reactions. For 10 points, name this class of reactions which forms long chains of monomers.
Tromsdorff's "gel effect" explains the increase in the rate of these reactions due to increased viscosity.
polymerizations [or addition polymerizations; or condensation polymerizations; or chain-growth polymerizations; or step-growth polymerizations; or radical polymerizations; or other types of polymerizations]