1.1. Ethyl 4-aminobenzoate, shown in Figure 1, is more commonly known as benzocaine. It is an ester based compound that is used medicinally as a local anaesthetic in pain relievers and cough drops.

Figure 1

One of the first industrial processes to manufacture benzocaine was the multi-step reaction shown in Figure 2.

Figure 2

The current cost of >99.7% pure benzene is around £10.00 per litre compared to > 99.5% pure methylbenzene at a cost of around £7.00 per litre.

Explain why it would be beneficial to start from methylbenzene instead of benzene in the manufacture of benzocaine. Your answer should not include economic considerations.

1.2. Concentrated sulphuric acid and concentrated nitric acid are used to form the nitronium ion required for step 2 of the reaction scheme, in part (a).

The following equilibrium is the first step in the formation of the nitronium ion.

H₂SO₄ + HNO₃ ⇋ HSO₄^- + H₂NO₃⁺

i) State the implications of this reaction in terms of the roles played by the acids. 

ii) Use your answer to part (i) to compare the strengths of the acids.

1.3. Give the reagents and conditions necessary for steps 4 and 5 of the reaction scheme shown in part (a).

1.4. A student suggests the reaction scheme shown in Figure 3 as an alternative to the original industrial reaction scheme shown in part (a) for the production of benzocaine.

Figure 3

i) State why the student’s reaction scheme is an improvement.

ii) Suggest why the student’s reaction scheme may not work.