Let's break down the problem step by step. ### Step 1: Identify the Reactants and Product - **Reactants:** Cyclohexane (C₆H₁₂) and isopropyl bromide (or isopropyl chloride, C₃H₇X) - **Product:** sec-Butylcyclohexane ### Step 2: Compare the Structures Product: The product is cyclohexane with a sec-butyl (–CH(CH₃)CH₂CH₃) group attached. ### Step 3: Analyze Carbon Sources - Cyclohexane provides the cyclohexyl ring (6 carbons). - Isopropyl group (from isopropyl halide) has 3 carbons. - The sec-butyl group has 4 carbons: CH(CH₃)CH₂CH₃. Thus, we need to combine the isopropyl group and one more carbon to get sec-butyl. ### Step 4: Reaction Mechanism The most logical reaction is a **Friedel–Crafts alkylation**. #### Friedel–Crafts Alkylation Steps: 1. **Preparation of sec-butyl cation:** Isopropyl halide (e.g., isopropyl chloride, (CH₃)₂CHCl) cannot directly give a sec-butyl group. But if isopropyl halide reacts with an **alkene** in the presence of acid, it can form a sec-butyl group. However, with only the given reactants, another step is needed. 2. **Convert isopropyl halide to propene:** Isopropyl halide can undergo elimination (E2) to form propene (CH₂=CH–CH₃). **Reagent:** Strong base (e.g., KOH/EtOH) 3. **Friedel–Crafts Alkylation with Propene:** Cyclohexane + propene + acid (e.g., H₂SO₄ or AlCl₃) The propene forms a secondary carbocation (CH₃–CH⁺–CH₃) which adds to cyclohexane to give sec-butylcyclohexane. --- ## **Step-by-Step Solution** ### **Step 1: Convert isopropyl halide to propene** - Isopropyl halide + strong base → propene + halide ion ### **Step 2: Friedel–Crafts Alkylation** - Cyclohexane + propene + acid → sec-butylcyclohexane --- ## **Final Reaction Sequence** 1. **Elimination:** Isopropyl halide \(\xrightarrow{\text{KOH/EtOH}}\) propene 2. **Friedel–Crafts Alkylation:** Cyclohexane + propene \(\xrightarrow{\text{H}^+}\) sec-butylcyclohexane --- ## **Final Answer** **Reagents Needed:** 1. Strong base (KOH/EtOH) 2. Acid catalyst (H₂SO₄ or AlCl₃) **Steps:** 1. Isopropyl halide → propene (via elimination) 2. Cyclohexane + propene + acid → sec-butylcyclohexane --- ### **Summary Table** | Step | Reactant(s) | Reagent/Condition | Product | |------|-------------------------|-------------------|---------------------------| | 1 | Isopropyl halide | KOH/EtOH | Propene | | 2 | Cyclohexane + Propene | Acid (H₂SO₄/AlCl₃)| sec-Butylcyclohexane | --- ### **Explanation** - **All carbons** in the product come from the starting materials. - You use elimination followed by Friedel–Crafts alkylation to achieve the transformation. --- Let me know if you need the mechanism details or structures!