Halogenation of aromatic rings quiz

1. What type of reaction occurs when bromine reacts with an alkene like ethene?

a) Nucleophilic substitution
b) Electrophilic substitution
c) Electrophilic addition
d) Free radical substitution

2. What is the main visible change when bromine water reacts with cyclohexene?

a) The solution turns red
b) The solution stays brown
c) The solution decolourises
d) A pleasant aroma is produced

3. What type of reaction occurs when bromine reacts with benzene in the presence of a Lewis acid catalyst?

a) Electrophilic substitution
b) Free radical substitution
c) Electrophilic addition
d) Nucleophilic addition

4. Bromine water does not react with readily benzene because bromine is not a good enough .

5. What is the purpose of using a halogen carrier such as FeBr₃ in the bromination of benzene?

a) To remove a hydrogen atom on the benzene ring
b) To act as a solvent for the reaction
c) To supply bromide ions
d) To generate a stronger electrophile

6. A Lewis acid is an electron pair while a Lewis base is an electron pair .

7. What is the major product when ethene reacts with bromine water (aqueous bromine)?

a) 1,2-dibromoethane
b) 2-bromoethanol
c) Ethanol
d) 1,1-dibromoethane

8. The key structural difference between alkenes and benzene that affects their reactivity is that benzene has π electrons.

9. What does the FeBr₄^- ion do in the final step of the bromination of benzene?

a) Forms a covalent bond to a bromine atom
b) Removes a hydrogen ion from the benzene ring
c) Supplies a bromine free radical
d) Adds to the benzene ring

10. Why is electrophilic substitution the preferred mechanism in the reactions of benzene and other aromatic molecules?

a) It avoids the loss of aromaticity in benzene
b) It is a much faster reaction than electrophilic addition
c) It requires a lower activation energy than electrophilic addition
d) It is a much "cleaner" reaction and produces fewer unwanted products

11. Which statement below best describes the delocalisation of the π electrons in benzene?

a) They are delocalised between two carbon atoms
b) They are free to leave the molecule
c) They are spread over all the carbon atoms in the benzene ring
d) They are free to move between alternate carbon atoms

12. During the bromination of benzene the delocalised π electron system is temporarily during the intermediate stage of the reaction however with the loss of a ion from the benzene ring it is restored at the end stage of the reaction.

13. Which of the following is not commonly used as a halogen carrier?

a) FeBr₃
b) AlCl₃
c) FeCl₃
d) NaBr

14. Which gas is produced during the bromination of benzene?

a) Bromine gas
b) Hydrogen bromide gas
c) Ethane gas
d) Steam

15. Bromine is more soluble in solvents such as cyclohexane or chloroform than it is in water.