Chemistry 9701 · AS & A Level · 8.1

8.1 — practice question

(a)[4]

Describe and explain the shape of benzene. In your answer, include: • the shape of the ring and the bond angle • the hybridisation of the carbon atoms • how orbital overlap produces $\sigma$ and $\pi$ bonds between the carbon atoms in the ring.

(b(i))[2]

Fig. 5.1 shows two reactions of benzoic acid. Suggest reagents and conditions for reaction 5 and for reaction 6 in Fig. 5.1. reaction 5 reaction 6

(b(ii))[1]

State the reaction type shown for reaction 5 in Fig. 5.1.

(c(i))[1]

In the electrophilic substitution of arenes, different substituents can direct to different ring positions. Describe the directing effect of the $\mathrm{-CH_2CH_3}$ group. Explain your answer.

(c(ii))[1]

The alkylation of arenes uses a mixture of $\mathrm{CH_3CH_2Br}$ and $\mathrm{FeBr_3}$ to generate the $\mathrm{CH_3CH_2^+}$ electrophile. Write an equation for the formation of the $\mathrm{CH_3CH_2^+}$ electrophile.

(c(iii))[3]

Complete the mechanism in Fig. 5.2. Include all relevant curly arrows and charges. Draw the structure of the organic intermediate.

(c(iv))[1]

Write an equation to show how $\mathrm{FeBr_3}$ is regenerated after the reaction in Fig. 5.2.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: (hexagonal ring) flat / (trigonal) planar

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