Let's break down the solution for the **addition of HBr to styrene (C₆H₅-CH=CH₂)** under **two conditions**: --- ## **1. Addition of HBr to Styrene in the Absence of Peroxides (Markovnikov Addition)** ### **Step 1: Protonation of the Double Bond** - The π electrons of the alkene attack the proton (H⁺) from HBr. - The benzyl position (CH₂ next to the benzene ring) stabilizes the carbocation via resonance, so the **more stable carbocation is formed at the benzylic position**. **Curved Arrow Mechanism:** - Double bond electrons form a bond with H⁺, generating a carbocation. **Intermediate:** ```plaintext H | C6H5-CH-CH3 (benzylic carbocation) + ``` ### **Step 2: Nucleophilic Attack by Bromide Ion** - Br⁻ attacks the carbocation. **Product:** ```plaintext Br | C6H5-CH-CH3 (Markovnikov product) ``` ### **Summary Mechanism (Markovnikov):** 1. Electrons from the double bond attack H⁺ → benzylic carbocation (stabilized by resonance). 2. Br⁻ attacks carbocation → **C6H5-CH(Br)-CH3**. --- ## **2. Addition of HBr to Styrene in the Presence of Peroxides (Anti-Markovnikov Addition, Free Radical Mechanism)** ### **Step 1: Initiation (Formation of Br Radical)** - Peroxide decomposes to form alkoxy radicals. - Alkoxy radical abstracts H from HBr → Br• radical is formed. ### **Step 2: Propagation (Radical Addition)** - The Br• radical adds to the **less substituted carbon** of the double bond (terminal carbon) to produce the more stable benzylic radical. **Intermediate:** ```plaintext C6H5-CH•-CH2Br (benzylic radical) ``` ### **Step 3: Radical Abstraction of H from HBr** - The benzylic radical abstracts H from another molecule of HBr, regenerating Br•. **Product:** ```plaintext C6H5-CH2-CH2Br (Anti-Markovnikov product) ``` ### **Summary Mechanism (Anti-Markovnikov):** 1. Br• adds to terminal carbon → benzylic radical. 2. Benzylic radical abstracts H from HBr → **C6H5-CH2-CH2Br**. --- ## **Final Answers (with Structures):** ### **Markovnikov Product (No Peroxides):** ``` Br | C6H5-CH-CH3 ``` **Name:** 1-Phenyl-1-bromopropane ### **Anti-Markovnikov Product (With Peroxides):** ``` C6H5-CH2-CH2Br ``` **Name:** 1-Phenyl-2-bromopropane --- ## **Electron Flow with Curved Arrows (Summary):** ### **Markovnikov:** 1. π electrons (double bond) → H⁺ of HBr; Br⁻ leaves. 2. Carbocation stabilized by resonance. 3. Br⁻ attacks carbocation. ### **Anti-Markovnikov:** 1. ROOR → 2RO• (heat/light). 2. RO• + HBr → ROH + Br• 3. Br• + alkene → benzylic radical. 4. Benzylic radical + HBr → product + Br• --- If you need **illustrated curved arrow mechanisms**, let me know, and I can provide them as diagrams!