Question

How does the presence of benzoquinone inhibit the free radical polymerisation of a vinyl derivative?

Answer 1

In the free radical polymerization of vinyl derivative, a reactive intermediate($R^{\ast }$) is formed which is responsible for the further progress of the chain reaction. Benzoquinone traps this reactive intermediate radical and changes it into non-reactive radical by stabilising it through resonance. In the absence of this reactive intermediate, further progress of the chain reaction is stopped.