# Step-by-Step Solutions --- ## **3. Arrow-Pushing and Mechanism** ### **i. Mechanism for Dimerization of 1-Phenyl-1-butene** **Reaction:** 2 × 1-Phenyl-1-butene + H₂SO₄/H₂O → A (linear dimer) + B (cyclic alcohol dimer) #### **Step 1: Protonation** - The alkene is protonated by H₂SO₄, generating a carbocation at the benzylic position (resonance stabilized). #### **Step 2: Nucleophilic Attack** - Another molecule of 1-phenyl-1-butene attacks the carbocation, generating a longer carbocation (dimeric intermediate). #### **Step 3: Deprotonation or Cyclization** - **For A:** Deprotonation leads to the linear dimer (A). - **For B:** Intramolecular cyclization occurs, followed by water addition and deprotonation, forming the cyclic alcohol (B). #### **Arrow-Pushing Steps:** 1. Protonation of alkene (double bond attacks H⁺, forms carbocation at benzylic position). 2. Second alkene attacks carbocation (forms new C–C bond, now another carbocation). 3. For A: Deprotonation at adjacent carbon to restore alkene. 4. For B: Intramolecular attack forms ring, then water attacks carbocation, followed by deprotonation to give alcohol. --- ### **ii. Acid-promoted Hydroalkoxylation of Strain-Release Bicyclobutanes** **Reaction:** Chlorobicyclobutane + 1-pentanol + H₃O⁺ → Ring-opened ether #### **Step 1: Protonation** - Ether oxygen (from pentanol) is protonated, making it a better nucleophile. #### **Step 2: Ring Opening** - The strained bicyclobutane is protonated at the bridgehead, making it susceptible to nucleophilic attack. #### **Step 3: Nucleophilic Attack** - Protonated pentanol attacks the more substituted carbon, opening the ring to form the ether. #### **Step 4: Deprotonation** - Loss of a proton gives the final ether product. #### **Arrow-Pushing Steps:** 1. Protonation of pentanol. 2. Attack of pentanol on the bicyclobutane (ring opens, forms new C–O bond). 3. Deprotonation to yield the final ether. --- ## **4. IUPAC Nomenclature** ### **First Compound** #### **Structure Analysis** - Cyclooctane (8-membered ring) parent. - Substituents: 4-chloro, 2,3-diol (vicinal diol). - Stereochemistry: (2R,3S) or as given from the image. #### **Name Breakdown** - **Parent:** cyclooctane - **Substituents:** 2,3-diol, 4-chloro - **Stereochemistry:** (2R,3S) - **Full IUPAC Name:** **(2R,3S)-4-chlorocyclooctane-2,3-diol** --- ### **Second Compound** #### **Structure Analysis** - Benzene ring parent. - Substituents: 2-hydroxy (ortho to S), 5-mercapto (meta to OH). - Stereochemistry: (1S,2R) or as given. #### **Name Breakdown** - **Parent:** benzene (phenol base) - **Substituents:** 2-hydroxy, 5-mercapto - **Stereochemistry:** (1S,2R) - **Full IUPAC Name:** **(1S,2R)-2-hydroxy-5-mercaptocyclohex-1-ylbenzene** *(If the ring is cyclohexanol and substituents are at 1 and 4, adjust as per actual structure; use correct locants!)* --- ## **5. Synthetic Route** **Goal:** Synthesize the rightmost product from the leftmost starting material. #### **Step 1: Oxidation** - Oxidize the secondary alcohol to a ketone (using PCC, Jones, or Swern oxidation). #### **Step 2: Stereoselective Reduction** - Reduce the ketone back to an alcohol using a stereoselective reducing agent (e.g., L-Selectride or a chiral catalyst) to get the opposite stereochemistry. #### **Stepwise Intermediates:** 1. Starting material (secondary alcohol) 2. Ketone intermediate 3. Final product (secondary alcohol with opposite stereochemistry) --- ## **Summary Table** | Problem | Main Concept | Key Steps | |---------|-------------|-----------| | 3(i) | Electrophilic alkene dimerization | Protonation, nucleophilic attack, cyclization/deprotonation | | 3(ii) | Acid-promoted ring opening | Protonation, nucleophilic attack, ring opening | | 4 | IUPAC naming | Identify parent, substituents, stereochemistry | | 5 | Synthetic strategy | Oxidation, stereoselective reduction | --- ### **Let me know if you need any mechanism drawings or further details!**