Aromaticity Questions - Organic Chemistry PDF

1. What is the shape of a benzene molecule? * A) Tetrahedral * B) Trigonal Planar * C) Planar * D) Pyramidal 2. What is the term used to describe the type of bonding in benzene? * A) Localised bonding. * B) Delocalised bonding. * C) Ionic bonding * D) Metallic bonding 3. Which of the following bes...

1. What is the shape of a benzene molecule? * A) Tetrahedral * B) Trigonal Planar * C) Planar * D) Pyramidal 2. What is the term used to describe the type of bonding in benzene? * A) Localised bonding. * B) Delocalised bonding. * C) Ionic bonding * D) Metallic bonding 3. Which of the following best describes the carbon-carbon bond lengths in benzene? * A) All bonds are single bonds. * B) All bonds are double bonds. * C) Alternating single and double bonds. * D) All bonds are identical and intermediate between single and double bonds. 4. What is the C-C-C bond angle in benzene? * A) 90° * B) 109.5° * C) 120° * D) 180° 5. Which orbitals overlap to form the delocalised pi system in benzene? * A) s orbitals * B) p orbitals * C) sp hybrid orbitals * D) sp2 hybrid orbitals 6. How many electrons are contained within the delocalised pi system in benzene? * A) 2 * B) 4 * C) 6 * D) 8 7. What is the general mechanism for the reactions of benzene? * A) Nucleophilic addition * B) Electrophilic addition * C) Electrophilic substitution * D) Nucleophilic substitution 8. What is the role of the catalyst in the nitration of benzene? * A) To act as a nucleophile. * B) To generate the electrophile. * C) To act as a solvent. * D) To neutralize the acid. 9. What is the electrophile in the nitration of benzene? * A) NO3- * B) NO2+ * C) NO+ * D) HNO3 10. Which of the following equations correctly represents the overall reaction for the nitration of benzene? * A) C6H6 + HNO3 → C6H5NO2 + H2 * B) C6H6 + HNO3 → C6H5NO2 + H2O * C) C6H6 + HNO2 → C6H5NO + H2O * D) C6H6 + NO2 → C6H5NO2 + H 11. What are the reagents used in the Friedel-Crafts alkylation of benzene? * A) A haloalkane and a strong base * B) An acyl chloride and a Lewis acid catalyst * C) A haloalkane and a Lewis acid catalyst * D) An alcohol and a strong acid catalyst 12. What is the electrophile in Friedel-Crafts alkylation? * A) R+ * B) RCl+ * C) AlCl4- * D) R- 13. What catalyst is used in Friedel-Crafts alkylation? * A) conc. H2SO4 * B) AlCl3 * C) Sn * D) FeBr3 14. Which of the following equations represents the formation of the electrophile in Friedel-Crafts alkylation using a haloalkane? * A) RCl + AlCl3 → R+ + AlCl4- * B) RCl + H2SO4 → ROH + HCl + SO3 * C) RCl + AlCl3 → R- + AlCl2+ * D) CH3Cl + H+ → CH4 + Cl+ 15. What is the electrophile in Friedel-Crafts acylation? * A) R+ * B) RCO+ * C) RCOO- * D) R-Cl+ 16. What is the product formed when benzene reacts with ethanoyl chloride in the presence of AlCl3? * A) Benzaldehyde * B) Phenylethanone * C) Ethylbenzene * D) Benzoic acid 17. What is the purpose of using anhydrous conditions in Friedel-Crafts reactions? * A) To increase the reaction rate. * B) To prevent the hydrolysis of the Lewis acid catalyst. * C) To shift the equilibrium towards the products. * D) The increase the overall yield. 18. What is the catalyst used in the bromination of benzene? * A) AlBr3 * B) FeBr3 * C) HBr * D) Br2 19. Which of the following equations best represents the overall reaction for the bromination of benzene? * A) C6H6 + Br2 → C6H5Br + HBr * B) C6H6 + 2Br2 → C6H4Br2 + 2HBr * C) C6H6 + Br2 → C6H6Br2 * D) C6H5Br + HBr 20. How many pi electrons are involved in the partial positive charge of the intermediate of the electrophilic substitution of benzene? * A) 2 * B) 4 * C) 6 * D) 8 Answers and Explanations: 1. C - Benzene is a planar molecule. 2. B - The pi electrons are delocalised. 3. D - All C-C bonds are the same length, somewhere between a single and a double. 4. C - 120° bond angles due to trigonal planar arrangement around each carbon. 5. B - p orbitals overlap above and below the plane of the ring. 6. C 7. C - Electrophilic substitution. 8. B - The catalyst helps generate the electrophile (e.g., NO2+). 9. B 10. B - This shows the correct reactants and products, including the water molecule formed. 11. C - A haloalkane (RCl) and a Lewis acid catalyst (e.g., AlCl3) are used. 12. A 13. B 14. A - This shows the generation of the carbocation (R+) electrophile. 15. B 16. B - Ethanoyl chloride reacts with benzene to produce phenylethanone. 17. B - Water would react with and deactivate the AlCl3 catalyst. 18. B 19. A 20. B Four pi electrons remain in the intermediate. Powered by pmfm.ai Request Support