Medium: monosubstituted, conjugated alkenes
Propose a reason why the medium group undergoes more rapid polymerisation than the slow group.Ī) Fast: disubstituted, conjugated alkenes. Propose a reason why the fast group undergoes more rapid polymerisation than the other groups. For each of the three groups (fast, medium and slow), identify what structural features the members of the group have in common that distinguishes them from the other groups. The figure below shows a number of monomers that are commonly polymerised under radical conditions. Radical polymerisation is a critical method of preparing polymers. One way would be to take some styrene, heat it up until it melts, and add some benzoyl peroxide. There are lots of ways to carry out this reaction. As a result, the newly-formed radical just gobbles up another alkene. Either they are very concentrated in solution or else they are neat (with no solvent at all). However, in a polymerisation reaction, alkene molecules are intentionally packed closely together. The newly-formed radical, in regular alkene addition, would then react with something to abstract an atom and achieve stable, closed-shell configuration. During the reaction, a radical adds to the double bond of the alkene. Polystyrene is one example of a material that is frequently prepared via radical conditions. 
This step is really a propagation step in terms of types of radical elementary reactions, because one radical leads to a new radical. That radical then initiates chain growth. The radical initiator has already undergone its reaction to form a radical. The term "initiator" here is used in a slightly different way than we have used it with other radical reactions. A chain reaction results in which other alkenes are enchained into a polymer.
Like other polymerisation reactions involving alkenes, it involves the formation of a reactive intermediate by the action of an initiator on an alkene. Radical addition to alkenes can be applied to the production of macromolecules.
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