Ethanedioyl dichloride, ClCOCOCl, is a useful reagent in organic synthesis. It can be made from compound A in one step. [Figure 7.1] Ethanedioyl dichloride is used in the following synthesis of compound Q. It is used in a 1:1 stoichiometric ratio with B in step 2. [Figure 7.2]

1. (a)(i)Suggest the identity of compound A by drawing its structure in the box.[1]
2. (a)(ii)State the reagents and conditions needed to convert A into ClCOCOCl.[1]
3. (b)(i)Suggest the identities of the compounds B-E by drawing their structures in the boxes.[4]
4. (b)(ii)State the reagents and conditions for the following steps. step 1 step 3 step 4 step 6[5]
5. (b)(iii)If the amount of ClCOCOCl used in step 2 is decreased, another compound is formed in step 2 with the molecular formula C₁₄H₈O₂Cl₂. Suggest the structure of this compound.[1]
6. (b)(iv)Identify all the steps in the synthesis of Q from benzene that are electrophilic substitution reactions.[1]
7. (c)Draw structures of the compounds formed when Q is treated with the following reagents. If there is no reaction, write 'no reaction' in the box. heat with Cr₂O₇²⁻/H⁺(aq) heat with NaOH(aq) Br₂(aq) HCl(aq) room temperature[4]

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.