Benzoquione combines with free radical intermediate to form a non-reactive free radical, which is highly stabilized by resonance, free radical, which is highly stabilized by resonanace. Because of the lack of reactivity of this intermediate, it inhibits the further progress of the chain reaction and the reaction stops.
![image](https://learnqa.s3.ap-south-1.amazonaws.com/images/16096514442045232304nlU9u0HiSreiOftY.png)