Let's solve each problem **step by step** with clear explanations: --- ## **2. Kevlar Polymerization** ### **a. Draw the repeat unit of Kevlar (4 pts)** **Monomers:** - Left: *Terephthalic acid* (benzene-1,4-dicarboxylic acid) - Right: *p-Phenylenediamine* (benzene-1,4-diamine) **Condensation Reaction:** - The carboxylic acid (-COOH) reacts with the amine (-NH₂) to form an **amide** (specifically, an *aramid*). **Repeat Unit:** ``` –[O=C–C₆H₄–C=O–NH–C₆H₄–NH]– ``` Or visually: ``` O O || || –[–C–C6H4–C–NH–C6H4–NH–]– ``` Where C₆H₄ is a para-substituted benzene ring. --- ### **b. Identify the two reactant functional groups and the functional group of the linkage formed (6 pts)** - **Reactant Functional Groups:** 1. **Carboxylic Acid** (-COOH) from terephthalic acid. 2. **Amine** (-NH₂) from p-phenylenediamine. - **Functional Group Formed:** - **Amide Linkage** (–CONH–). --- ## **3. Stiffness of Kevlar and Kodel vs. Nylon (10 pts)** **Reason:** - **Kevlar and Kodel:** Both have aromatic rings in their backbone, which are rigid and planar, restricting rotation and making the fibers stiff. - **Nylon:** Contains aliphatic (non-aromatic) segments, allowing more flexibility and rotation along the polymer chain. **Conclusion:** *The presence of aromatic rings in Kevlar and Kodel leads to increased stiffness compared to Nylon, which has more flexible aliphatic chains.* --- ## **4. Polymerization Reaction** ### **a. Draw the repeat unit of the polymer (6 pts)** - The given reaction is between **terephthalic acid** and **ethylene glycol** (a diol). - This forms a **polyester** (specifically, PET - Polyethylene Terephthalate). **Repeat Unit:** ``` O O || || –[–C–C6H4–C–O–CH2–CH2–O–]– ``` Where C₆H₄ is a para-substituted benzene ring. --- ### **b. What functional group is formed? (4 pts)** - **Ester Functional Group** (–COO–). --- ## **5. Ring-Opening Polymerization Mechanism (10 pts)** **Monomer:** - Caprolactam (a cyclic amide) **Mechanism:** 1. Base deprotonates the amide nitrogen. 2. The negatively charged nitrogen attacks the carbonyl carbon of another caprolactam ring, breaking the amide bond and opening the ring. 3. This repeats, forming **Nylon-6**. **General Repeat Unit:** ``` –[–NH–(CH₂)₅–CO–]– ``` **Mechanism Steps (drawn):** 1. Base abstracts a proton from NH. 2. The anionic N attacks another monomer's carbonyl C, opening the ring. 3. Propagation continues, yielding a linear polyamide. --- ### **Summary Table** | Q | Monomers/Repeat Unit | Functional Groups | Linkage Formed | |---|----------------------|------------------|---------------------| | 2 | Kevlar: –[–C₆H₄–CO–NH–C₆H₄–NH–CO–]– | –COOH, –NH₂ | Amide (–CONH–) | | 4 | PET: –[–C₆H₄–CO–O–CH₂–CH₂–O–CO–]– | –COOH, –OH | Ester (–COO–) | | 5 | Nylon-6: –[–NH–(CH₂)₅–CO–]– | Lactam (ring amide) | Amide (–CONH–) | --- If you need the full arrow-pushing mechanism for Question 5 or structural diagrams, let me know!