Sure! Let's break down each part of the questions with **clear explanations and stepwise reasoning**. --- # Question c: Synthesis from Benzene/Toluene ### General Approach: - **Identify substituent effects** (activating/deactivating, ortho/para/meta directors). - **Plan order of reactions** to control positions of substituents. - **Remember**: Ortho/para isomers can be separated. --- ## i)  **Structure**: 3-nitro-4-chlorobenzoic acid **Target:** - Nitro (NO₂) at position 3 - Chloro (Cl) at position 4 - Carboxylic acid (COOH) at position 1 ### **Stepwise Synthesis:** 1. **Start with benzene.** 2. **Friedel-Crafts Acylation** to introduce COOH group (by first making benzophenone, then oxidizing): - Benzene → Benzaldehyde (Gattermann-Koch formylation) - Benzaldehyde → Benzoic acid (oxidation: KMnO₄) 3. **Nitration** (NO₂ is meta director; will go to position 3) - Benzoic acid → meta-nitrobenzoic acid (HNO₃/H₂SO₄) 4. **Chlorination** (Cl is ortho/para director; but COOH is meta director, so Cl will go to position 4) - Nitrated benzoic acid → 4-chloro-3-nitrobenzoic acid (Cl₂/FeCl₃) --- ## ii) **Structure:** - Amino (NH₂) at position 1 - tert-butyl (C(CH₃)₃) at position 4 - Methyl (CH₃) at position 2 ### **Stepwise Synthesis:** 1. **Start with toluene** (methyl group is ortho/para director). 2. **Friedel-Crafts Alkylation** to add tert-butyl group at para position. - Toluene + t-butyl chloride/AlCl₃ → p-tert-butyl toluene 3. **Nitration** (NO₂ goes to ortho position due to both CH₃ and t-butyl being ortho/para directors) - p-tert-butyl toluene + HNO₃/H₂SO₄ → ortho-nitro derivative 4. **Reduction** of nitro group to amine: - Sn/HCl or Fe/HCl → ortho-amino derivative --- ## iii) **Structure:** - Acetylamino (NHCOCH₃) at position 4 - Ethyl (CH₂CH₃) at position 2 - Chloro (Cl) at position 1 ### **Stepwise Synthesis:** 1. **Start with chlorobenzene** (Cl is ortho/para director). 2. **Friedel-Crafts Alkylation** to add ethyl group at ortho position. - Chlorobenzene + ethyl chloride/AlCl₃ → ortho-ethylchlorobenzene 3. **Nitration** (NO₂ goes para to Cl, which is position 4) - ortho-ethylchlorobenzene + HNO₃/H₂SO₄ → 4-nitro derivative 4. **Reduce NO₂ to NH₂**: - Sn/HCl or Fe/HCl 5. **Acetylation** (NH₂ + CH₃COCl → NHCOCH₃) --- # Question d: Why *meta* substitution in benzaldehyde? ## **Resonance Explanation:** - **Benzaldehyde:**  - The formyl group (-CHO) is **electron withdrawing**. - When an electrophile attacks the **ortho/para** position, resonance forms positive charge at the carbon attached to -CHO, which is destabilized by the electron-withdrawing nature of the group. - At the **meta** position, resonance does **not** place positive charge on the carbon with the -CHO group, making it more stable and thus more favorable. **Summary:** Electrophilic substitution occurs at the meta position because the ortho/para positions would result in a resonance structure with a highly unstable carbocation adjacent to the electron-withdrawing -CHO group. --- # Question 3 ## a) **Sulphonation of Naphthalene** - **Naphthalene** reacts with concentrated H₂SO₄ to form naphthalenesulphonic acid. - At **low temperature** (~40°C), the major product is **α-naphthalenesulphonic acid** (position 1). - At **high temperature** (~160°C), the **β-isomer** (position 2) predominates. - Reaction is **reversible** (desulphonation can occur with steam). --- ## b) **Predict Products** ### i) - **1-nitronaphthalene** + Br₂/FeBr₃ - **NO₂ is meta-directing, so Br will go to position 3.** - **Product:** 3-bromo-1-nitronaphthalene ### ii) - **Furan-2-carbaldehyde** + Ag₂O (oxidation) - **Product G:** Furan-2-carboxylic acid - **Heating at 200°C:** Decarboxylation - **Product H:** Furan --- ## c) **Synthesis of 4-aminopyridine from pyridine** ### **Method:** 1. **Nitration of pyridine** (not easy directly, but can do via oxidation to 4-pyridinecarboxylic acid, amination, then reduction). 2. **Chlorination to 4-chloropyridine** (via Sandmeyer reaction from 4-aminopyridine). 3. **Amination** (nucleophilic aromatic substitution): - 4-chloropyridine + NH₃ → 4-aminopyridine --- Let me know if you need any reaction mechanisms or further details on any part!

# Summary of Reactions and Concepts ## Synthesis from Benzene/Toluene ### 1. **Compound i: 3-Nitro-4-chlorobenzoic Acid** - **Starting Material**: Benzene - **Synthesis Steps**: 1. Friedel-Crafts Acylation to add COOH (benzoic acid). 2. Nitration to introduce NO₂ at position 3. 3. Chlorination to add Cl at position 4. ### 2. **Compound ii: 4-Amino-2-tert-butyl-1-methylbenzene** - **Starting Material**: Toluene - **Synthesis Steps**: 1. Friedel-Crafts Alkylation to add tert-butyl at para position. 2. Nitration to introduce NO₂ at ortho position. 3. Reduction of NO₂ to NH₂. ### 3. **Compound iii: 4-Acetylamino-2-ethyl-1-chlorobenzene** - **Starting Material**: Chlorobenzene - **Synthesis Steps**: 1. Friedel-Crafts Alkylation to add ethyl at ortho position. 2. Nitration to introduce NO₂ at para position. 3. Reduction of NO₂ to NH₂. 4. Acetylation to introduce NHCOCH₃. --- ## Electrophilic Substitution Preference - **Meta Position Preference**: - In benzaldehyde, the -CHO group is electron-withdrawing, destabilizing ortho/para carbocations. - Meta substitution results in a more stable resonance form. --- ## Sulphonation of Naphthalene - **Products**: α-naphthalenesulphonic acid (low temp) and β-naphthalenesulphonic acid (high temp). --- ## Product Predictions ### i) **1-Nitronaphthalene + Br₂/FeBr₃** - **Product**: 3-bromo-1-nitronaphthalene. ### ii) **Furan-2-carbaldehyde + Ag₂O** - **Product G**: Furan-2-carboxylic acid. - **Heating at 200°C** results in **Product H**: Furan. --- ## Synthesis of 4-Aminopyridine ### Method Overview: 1. **Nitration of Pyridine** to get 4-pyridinecarboxylic acid. 2. **Chlorination** to form 4-chloropyridine. 3. **Amination** using NH₃ to yield 4-aminopyridine. --- Feel free to ask if you need further clarification on any topic!