JPJC 2026 Arenes Tutorial

2026 JPJC JC1 H2 Chemistry 1 Topic 11: Arenes JURONG PIONEER JUNIOR COLLEGE 2026 JC1 H2 Chemistry Tutorial 11: Arenes Level 1 – Self–Check Questions Comparing reactivity of alkene versus benzene 1 (a) Both ethene and benzene react with chlorine, but the mechanisms and the types of products of the two reactions are different. (i) State the required conditions and the type of reaction undergone when ethene and benzene are reacted with chlorine separately. (ii) Describe the mechanism for the reaction of chlorine and benzene. Include the structure of the intermediate, relevant charges and curly arrows to show the movements of electrons. (iii) Explain why ethene and benzene differ in their type of reaction with chlorine and reaction conditions. (b) Benzene can be nitrated by warming it with a mixture of concentrated sulfuric acid and nitric acid. (i) By means of an equation, explain the role of concentrated sulfuric acid. (ii) Name and describe the mechanism for the reaction. Include all relevant charges and curly arrows showing the movements of electrons. (iii) State the conditions needed for the nitration of methylbenzene. Explain why benzene and methylbenzene require different conditions in their reaction with nitric acid. 2 (a) Benzene reacts with X in the presence of a suitable catalyst, Y, to give W and non- organic product Z. This is an electrophilic substitution reaction. (i) Suggest the reactant X, catalyst Y and non-organic product Z. (ii) Hence, describe the mechanism for the above reaction, including the structures of any intermediates, relevant charges and curly arrows to show the movements of electrons. (b) Describe the conditions that are used to ensure substitution takes place only in the side-chain. (c) Draw the structure of the organic product formed when W reacts with H 2 gas in the presence of nickel at high pressure. Hint: To get the electrophile E+, the atom directly bonded to benzene will bear the +ve charge in E+. W

2026 JPJC JC1 H2 Chemistry 2 Topic 11: Arenes Comparing e lectrophilic substitution of benzene versus alkylbenzene + free radical substitution of (alkyl group of) alkylbenzene 3 (a) By describing the reaction conditions, products and site of attack, and rate of reaction , compare and contrast all possible types of reactions of chlorine with benzene and methylbenzene. (b) Draw the mechanism of the reaction between methylbenzene and chlorine, in the presence of AlCl3, showing any intermediates. Oxidation of alkyl side-chain of alkylbenzene 4 Draw the structure of the organic product formed when cumene is heated with KMnO 4(aq), H2SO4(aq). On Naming and Isomerism of aromatic compounds 5 Draw the displayed formulae of the following compounds. (a) 1,3–dimethylbenzene (b) 1–phenylpropene (c) 2–bromoethylbenzene Level 2 – Application Questions 6 A level N2017/P3/Q1(d) When benzene is heated with BrCl and AlCl3, a monohalogenobenzene, C6H5X, is formed. (a) Suggest whether the product C6H5X is chlorobenzene or bromobenzene. Give a reason for your answer. (b) Draw the mechanism of the reaction, showing any intermediates. [2] Checklist: Organic Chemistry Mechanism I can identify the correct mechanism and apply the correct concepts in organic chem to draw the mechanism.  Have I identified if it is a substitution or addition?  Have I identified whether the carbon-containing functional group is electron-rich, electron-deficient? o If it is electron-rich, it attracts electrophiles o If it is electron-deficient, it attracts nucleophiles o If it is neither electron -rich or electron -poor, it can only be forced to react via free radical substitution  Did I draw correct arrows to show how electrons flow from electron-rich to electron-poor species?  Did I draw the correct intermediate formed?  Have I balanced all equations? Have I labelled the slow and fast steps?

2026 JPJC JC1 H2 Chemistry 3 Topic 11: Arenes Mechanism 7 2012/P3/Q1(c) modified Aluminium chloride is used as a catalyst in electrophilic substitution reactions. The chlorination of benzene is represented by the following overall equation. The reaction occurs in several steps. • The first step is the reaction between Cl2 and AlCl3. Cl2 + AlCl3 ⎯→ Cl+ + AlCl4− • The benzene ring is then attacked by the Cl+ cation in the second step. AlCl3 reacts in a similar way with acyl chlorides, producing a carbocation that can then attack a benzene ring. (a) (i) Suggest the structure of the product of the following reaction. (ii) Hence, describe the mechanism for the formation of A. Include in your answer, the structure of the intermediate, relevant charges and curly arrows to show the movements of electrons. (b) Predict the structure of the product B for the following reaction. (c) The following outlines reactions involving benzene. Give the reagents and conditions for steps 2 and 3. 1 Cl 2 3 Cl2 NO2 X Cl 4

2026 JPJC JC1 H2 Chemistry 4 Topic 11: Arenes 8 TYS 2018/P2/Q4(b)-(c) & 2021/P3/Q4(d) modified (a) Under suitable conditions, benzene can react with fuming sulfuric acid, H2S2O7. Assume that fuming sulfuric acid ionises as shown. H2S2O7  HSO4ꟷ + SO3H+ Suggest a mechanism for this reaction. Show the displayed structure of the electrophile, the structure of the intermediate cation and the movement of electron pairs by using curly arrows. (b) Methylbenzene reacts with fuming sulfuric acid, H 2S2O7, to form a mixture of three isomers, G, H and J, in equilibrium. The position of substitution in the electrophilic substitution of mono-substituted arenes depends on the nature of the group already attached to the ring. This selectivity can be explained based on the stability of the intermediate cation formed in the first step. Fig. 1 shows three possible first steps in the reaction of methylbenzene with H 2S2O7 and the products obtained. Figure 1 (i) Explain why H is the isomer least likely to be formed in this reaction. (ii) Suggest why there is a lower concentration of G than of J in the equilibrium mixture. G H J

2026 JPJC JC1 H2 Chemistry 5 Topic 11: Arenes (c) K also undergoes a reaction with fuming sulfuric acid. Suggest the order of reactivity of benzene, methylbenzene and K with fuming sulfuric acid. Explain your answer. Distinguishing tests & predicting oxidation of alkyl side-chains of alkylbenzenes Checklist: Organic Distinguishing tests  I can apply the correct concepts to identify the correct reagents and conditions for the distinguishing test to distinguish between the compounds.  Have I drawn out structures of the organic compounds? Have I identified the functional groups?  Does the reagent & condition proposed specifically react only with functional group in only 1 compound to give positive distinct observation?  Did I state observations for each compound? 9 (a) Describe a simple chemical test to distinguish the following pairs of substances. In your answer, state the reagents and conditions required and, state what would be observed. (i) (ii) CH2CH3 and CH=CH2 (b) Predict the organic products of the following reactions and draw their structures in the boxes below. Extension: What will the product be if NaOH(aq) is used in place of H2SO4(aq)? CH2CH3 CH3CH3and KMnO4(aq), H2SO4(aq), heat KMnO4(aq), H2SO4(aq), heat

2026 JPJC JC1 H2 Chemistry 6 Topic 11: Arenes Synthesis 10 Propose a synthetic route for the formation of each of the following compounds, using benzene as the starting material . In your answer, state clearly the reagents and conditions needed for each stage of the route and draw the structure (s) of the organic intermediate(s) involved.