Provide the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HBr, H₂O₂.
(d)

Verified step by step guidance

1. Identify the structure of the alkene in part (d). Alkenes are hydrocarbons with a carbon-carbon double bond, which is the site of reactivity in these reactions.
2. For the reaction with HBr (hydrobromic acid), apply Markovnikov's rule. This rule states that in the addition of HX to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached, and the halide (Br) will attach to the carbon with fewer hydrogen atoms.
3. Write the mechanism for the reaction with HBr. The double bond will attack the hydrogen in HBr, forming a carbocation intermediate on the more substituted carbon. The bromide ion will then attack the carbocation, resulting in the Markovnikov product.
4. For the reaction with HBr and H₂O₂ (hydrogen peroxide), apply anti-Markovnikov's rule. In the presence of peroxides, the addition of HBr to alkenes proceeds via a radical mechanism, where the bromine atom attaches to the less substituted carbon.
5. Write the mechanism for the reaction with HBr and H₂O₂. Initiation begins with the formation of radicals from H₂O₂. The alkene reacts with the bromine radical, forming a new radical on the less substituted carbon. This radical then reacts with HBr, completing the anti-Markovnikov addition.

Key Concepts

Markovnikov's Rule

Markovnikov's Rule states that in the addition of HX (where X is a halogen) to an alkene, the hydrogen atom will attach to the carbon with more hydrogen substituents, while the halogen will attach to the carbon with fewer hydrogen substituents. This rule helps predict the major product in electrophilic addition reactions.

Anti-Markovnikov Addition

Anti-Markovnikov addition occurs when HBr is added to an alkene in the presence of peroxides (H₂O₂). The reaction proceeds via a radical mechanism, leading to the bromine atom attaching to the less substituted carbon atom, opposite to Markovnikov's Rule. This results in the formation of the anti-Markovnikov product.

Radical Mechanism

A radical mechanism involves the formation of free radicals, which are highly reactive species with unpaired electrons. In the presence of peroxides, the addition of HBr to alkenes follows a radical pathway, initiating with the homolytic cleavage of the peroxide bond, leading to the generation of bromine radicals that drive the anti-Markovnikov addition.