Consider the free radical chain mechanism for the addition of to an alkene in the presence of peroxi — Reaction Mechanism Chemistry Question
Question
Consider the free radical chain mechanism for the addition of $HBr$ to an alkene in the presence of peroxides. How many distinct chemical steps are involved strictly in the "Chain Propagation" phase?
💡 Solution & Explanation
The chain propagation phase consists of exactly two repeating steps: Step 1 involves the attack of the bromine free radical ($Br^\cdot$) on the alkene $\pi$ -bond to form a carbon-centered free radical. Step 2 involves this new carbon free radical abstracting a hydrogen atom from a fresh molecule of $HBr$, generating the alkyl bromide product and regenerating a $Br^\cdot$ radical to continue the chain.