Electrophilic substitution: halogenation, nitration, Friedel-Crafts
- Among the following, the reaction that proceeds through an electrophilic substitution, is : Answer: 2. (structure 2, see figure): benzene + Cl ₂ xrightarrowAlCl₃ chlorobenzene + HCl (1) Sandmeyer reaction: via aryl radical / diazoni... 1
- Identify the major products P, Q and R in the following sequence of reactions :benzene + CH_3CH_2CH_2Cl Anhydrous AlCl_3 P ; P [(ii) H_3O^+/Δ](i) O_2 Q + R Answer: 4. P = cumene (C ₆ H ₅ CH(CH ₃ ) ₂ ), Q = phenol (C ₆ H ₅ OH), R = CH ₃ - CO - CH ₃ Friedel-Crafts alkylation with n-propyl chloride... 1
- Which of the following can be used as the halide component for Friedel-Crafts reaction? Answer: 3. Isopropyl chloride Key idea: Friedel-Crafts alkylation needs an alkyl halide that can give a carbocation. Aryl halides (bromobenz... 1
- In the given reaction [benzene + cyclohexene, HF, 0 C -> P] the product P is Answer: 2. [structure shown in figure] Key idea: HF protonates the alkene to give a carbocation, which alkylates benzene (Friedel-Crafts alk... 1
- Consider the nitration of benzene using mixed conc. H_2SO_4 and HNO_3. If a large amount of KHSO_4 is added to the mixture, the rate of nitration will be : Answer: 2. slower Key idea: nitration needs the nitronium ion, formed by HNO₃+2H₂SO₄⇌ NO₂^++H₃O^++2HSO₄^- KHSO₄ adds a large amount of HSO₄^... 1