The structure of benzene-1,3-dicarboxylic acid is shown. [Figure of benzene-1,3-dicarboxylic acid]

1. (a)State the empirical formula of benzene-1,3-dicarboxylic acid.[1]
2. (b)Benzene-1,3-dicarboxylic acid is an isomer of benzene-1,4-dicarboxylic acid. These two isomers can be distinguished by carbon-13 (¹³C) NMR spectroscopy. State the number of peaks in the carbon-13 (¹³C) NMR spectrum of each compound. benzene-1,3-dicarboxylic acid benzene-1,4-dicarboxylic acid[2]
3. (c)(i)Benzene-1,3-dicarboxylic acid can be made by the two-step synthesis shown below. [Figure reaction scheme with compound P, compound Q] Name compound P.[1]
4. (c)(ii)Explain why the major product of this two-step synthesis is benzene-1,3-dicarboxylic acid and not benzene-1,4-dicarboxylic acid.[1]
5. (c)(iii)The reagents used for step 1 are CH₃COCl and AlCl₃. These reagents give rise to CH₃C=O ions which react with compound P. Name the mechanism of this reaction.[1]
6. (c)(iv)Draw the mechanism of the reaction of CH₃C=O ions with compound P. Include all relevant curly arrows and charges, the structure of the intermediate and the structure of compound Q. [Figure CH₃C=O, HO benzene ring][3]
7. (c)(v)Suggest a reagent and conditions to convert compound Q into benzene-1,3-dicarboxylic acid, in step 2.[1]

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