Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

Fig. 7.1 shows the structural formulae and displayed formulae of three aromatic compounds, A, B and C.
(a)[3]

Compare the relative acidities of A, B and C. Explain your answer.

(b(i))[1]

Methylbenzene, $\text{C}_6\text{H}_5\text{CH}_3$, may be prepared from benzene by electrophilic substitution. Identify a compound that reacts with benzene to produce methylbenzene. Identify the catalyst used.

(b(ii))[1]

The first step in the reaction is the formation of the $\text{CH}_3^+$ electrophile. Write an equation for the reaction that produces this electrophile.

(b(iii))[3]

Describe the mechanism for the reaction between benzene and the $\text{CH}_3^+$ electrophile. Include all relevant curly arrows and charges.

(b(iv))[2]

Identify a suitable reagent to oxidise methylbenzene to benzoic acid, $\text{C}_6\text{H}_5\text{COOH$. Write an equation for this reaction using $[\text{O}]$ to represent one atom of oxygen from the oxidising agent.

(b(v))[1]

Methylbenzene and benzoic acid are each nitrated with concentrated nitric acid and sulfuric acid to form mononitrated products. Their structural formulae are $\text{CH}_3\text{C}_6\text{H}_4\text{NO}_2$ and $\text{HOOCC}_6\text{H}_4\text{NO}_2$ respectively. Draw the structures of these two products.

(c(i))[1]

A reaction scheme is shown in Fig. 7.2. Describe the reagents and conditions needed to produce $\text{CH}_3\text{C}_6\text{H}_4\text{N}_2^+\text{Cl}^-$ from $\text{CH}_3\text{C}_6\text{H}_4\text{NH}_2$ in reaction 2.

(c(ii))[1]

Describe how $\text{CH}_3\text{C}_6\text{H}_4\text{OH}$ can be produced from $\text{CH}_3\text{C}_6\text{H}_4\text{N}_2^+\text{Cl}^-$ in reaction 3.

(c(iii))[2]

Draw the structure of the dye molecule Y formed when $\text{CH}_3\text{C}_6\text{H}_4\text{N}_2^+\text{Cl}^-$ and $\text{CH}_3\text{C}_6\text{H}_4\text{OH}$ react together in reaction 4. Describe the conditions for this reaction.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: Acidity order is $\text{C} > \text{A} > \text{B}$

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