A-LevelChemistryOrganic synthesis9701/42 · Feb/Mar 2017 · Q59 Marks

(a) Compound H can be synthesised from benzene as shown. [Figure: Reaction scheme starting from benzene, going through step 1, then intermediate G, then step 2 with Cl2(g) to a branched alkylbenzene, then step 3 to Compound H (C10H13NH2)]

(a)(i)State the reagents and conditions needed for step 1. reagents conditions[2]
(a)(ii)Step 2 takes place in the presence of chlorine gas. State the conditions for this reaction.[1]
(a)(iii)Draw the structure of intermediate G in the box.[1]
(a)(iv)State the reagents and conditions needed for step 3. reagents conditions[2]
(b)Write an equation to show how compound H, C₁₀H₁₃NH₂, behaves as a base.[1]
(c)Compare the relative basicities of ammonia, phenylamine and compound H. Explain your answer.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2017). The mark or mark type is shown in brackets.

[1] (CH3)3C-Cl / (CH3)2C = CH2
[1] AlCl3 + heat
[1] Structure of intermediate G: [Benzene ring]-CH₂-C(CH₃)₂-Cl
[1] ammonia/NH3
[1] heat in sealed tube/heat under pressure
[1] C10H13NH2 + H3O+ ⇌ C10H13NH3+ + H2O (or +H+ ⇌ +H)
[1] in compound H, the alkyl groups are electron donating/have a positive inductive effect, so it is more basic than NH3
[1] in phenylamine, the lone pair (of N) is delocalised over the aryl group/benzene ring, so phenylamine is less basic than NH3

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