Let's break down and solve the problems step by step: --- ## 1. Predict the products and mechanisms ### (a) Benzene + HCl(g) **Reaction:** Benzene does not react with HCl(g) under these conditions because benzene is not reactive towards simple acids without a strong electrophile or catalyst (like AlCl₃ in Friedel-Crafts reactions). **Product:** No reaction. --- ### (b) 2-methylbut-2-ene + cat. HCl in methanol **Mechanism:** 1. Protonation of alkene forms a carbocation (markovnikov, more stable). 2. Carbocation intermediate. 3. Methanol attacks the carbocation (nucleophile). 4. Deprotonation gives the ether. **Product:** - The major product is **2-methoxy-2-methylbutane**. **Racemic?** - No chiral center is formed; product is **achiral**. --- ### (c) Cyclohexene + HBr(g) (inert solvent) **Mechanism:** 1. Protonation of alkene to carbocation (at more substituted carbon). 2. Bromide ion attacks the carbocation. **Product:** - **Bromocyclohexane** **Racemic?** - No chiral center is generated; product is **achiral**. --- ### (d) 2-methylbut-2-ene + HBr(g) in toluene **Mechanism:** 1. Protonation forms the most stable carbocation. 2. Br⁻ attacks carbocation. **Product:** - **2-Bromo-2-methylbutane** **Racemic?** - No chiral center; **achiral**. --- ### (e) Toluene + HCl(g) in dry toluene **Reaction:** No reaction under these conditions (toluene is not reactive with HCl without a strong electrophile/catalyst). **Product:** No reaction. --- ### (f) 3-pentene + cat. HCl(g) in methanol **Mechanism:** 1. Protonation of alkene at C-2 or C-3 gives the more stable secondary carbocation at C-3. 2. Methanol attacks carbocation, then deprotonation. **Product:** - **3-methoxypentane** **Racemic?** - If a stereocenter is formed, a racemic mixture forms. Here, the product is **achiral** (no stereocenter at C-3). --- ## 2. Carbocation Stability Draw hydrogens and rank stability: - (i) Cyclopropylmethyl carbocation (resonance stabilized) - (ii) Cyclohexyl carbocation (secondary) - (iii) Cycloheptyl carbocation (secondary) - (iv) Cyclopentyl carbocation (secondary) **Ranking:** **Cyclopropylmethyl > cycloheptyl ≈ cyclohexyl ≈ cyclopentyl** - Cyclopropylmethyl is more stable due to resonance (allylic stabilization). - The rest are secondary carbocations with little difference in stability. --- ## 3. (a) Cyclization with HO(CH₂)₄CH₃ + catalytic HCl in toluene ### Mechanism: 1. Protonation of the alcohol to form good leaving group (water). 2. Intramolecular attack by the terminal carbon (Friedel-Crafts-type cyclization). 3. Deprotonation to form cyclopentane ring. ### Product: - **Cyclopentylmethanol** (five-membered ring with methanol group attached). ### (b) Is the product chiral, racemic, or achiral? - The product is **achiral** as no chiral center is formed. --- ## **Summary Table** | Part | Product | Racemic/Achiral/Chiral | |------|---------|------------------------| | (a) | No reaction | - | | (b) | 2-methoxy-2-methylbutane | Achiral | | (c) | Bromocyclohexane | Achiral | | (d) | 2-bromo-2-methylbutane | Achiral | | (e) | No reaction | - | | (f) | 3-methoxypentane | Achiral | | 2 | Stability: cyclopropylmethyl > others | | | 3 | Cyclopentylmethanol | Achiral | --- ### Let me know if you want detailed curved-arrow mechanisms for any of these!