Halogen Compounds (Cambridge (CIE) A Level Chemistry): Exam Questions

This question is about halogenoarene compounds.

State the reagents and name of the mechanism used to convert benzene into chlorobenzene

Using your answer to (a), construct an equation for the generation of the ion which reacts with benzene.

Draw the mechanism for the chlorination of benzene.

Explain how the C–Cl bond in chlorobenzene prevents nucleophilic substitution from occurring.

Predict the products of the following reactions in Fig. 2.1 and draw their structures in the boxes provided. Note that the molecular formula of the final product is given in each case.

Fig. 2.1

Construct an equation for the generation of the electrophile when methylbenzene reacts with bromine and aluminium bromide.

Draw the reaction mechanism for the reaction of methylbenzene with bromine and aluminium bromide.

Explain why halogenoalkanes such as bromopropane are more reactive than halogenoarenes such as bromobenzene.

A student investigated two reactions of phenylethene, C₆H₅CH=CH₂ as shown in Fig. 3.1. First she reacted phenylethene with excess bromine at room temperature to form Compound A. She then added aluminium bromide, AlBr₃ to the reaction mixture to form Compound B.

Fig. 3.1

Draw the structures of Compounds A and B.

Name and outline the mechanism for the formation of Compound B from Compound A.

Nitrobenzene was reacted with aluminium chloride and chlorine. Name and draw the structure of the aromatic product formed in this reaction.

Nitration of a benzene ring forms nitrobenzene. The subsequent reactions of nitrobenzene are shown in Fig. 1.1.

Fig. 1.1

The structures of the products have the same molecular formula. Explain why these products are different. In your answer include the structures of compounds X and Y and reagents for reactions A and B. 

Using curly arrows, describe the mechanism for reaction A. 

State the IUPAC name of Compound Z and draw the structure.

Chlorobenzene is formed by bubbling chlorine gas into benzene at room temperature in the presence of anhydrous AlCl₃.

Explain, by the use of equations, how AlCl₃ acts as a catalyst in the chlorination of benzene.

Nitrobenzene undergoes further substitution considerably more slowly than chlorobenzene. In nitrobenzene, the incoming group joins the benzene ring in the 3-position, whereas in chlorobenzene the incoming group joins to the benzene ring in the 4-position. Use these ideas to suggest the structures of the intermediate compounds Y and Z in the following synthesis of 4-chlorophenylamine.

Suggest the structure of the organic product formed when 4-chlorophenylamine reacts with bromine water.

Fig. 3.1 shows two reactions of methylbenzene.

Fig. 3.1

i) State the conditions required for reaction 1.

[1]

ii) State the conditions required for reaction 2.

[1]

State the reagent needed to carry out the following reaction occurring in Fig. 3.2.

Fig. 3.2

The three chloro-compounds A, B and C vary in their ease of hydrolysis.

i) Place a tick in the box in Table 3.1 corresponding to the correct relative rates of hydrolysis. [the symbol '>' means 'faster than'].

Table 3.1

[1]

ii) Suggest an explanation for these differences in reactivity.

[2]