Ester X has the formula CH3COOR. R is an alkyl group with the general formula CnH2n+1. Ester X undergoes alkaline hydrolysis with aqueous potassium hydroxide, KOH(aq). The resulting mixture is acidified with dilute hydrochloric acid, HCl(aq). The organic products of the hydrolysis after acidification are ethanoic acid, CH3COOH, and an alcohol, ROH. Once the identity of ROH is found, the structure of ester X can then be determined. A student uses the following steps. step 1 Equal molar quantities of ester X and KOH(aq) are placed in a round-bottomed flask. step 2 A few drops of a suitable indicator are added to show whether a reaction has occurred. step 3 A substance is added to promote smooth boiling. step 4 The reaction mixture is set up for reflux and heated for 30 minutes. step 5 After 30 minutes, the reaction mixture in the round-bottomed flask is acidified by adding HCl(aq) dropwise. step 6 Thin-layer chromatography is carried out on the reaction mixture.

1. (a)(i)Complete the diagram in Fig. 2.1 to show the apparatus used for reflux in step 4. Label the diagram. heat [Figure 2.1][2]
2. (a)(ii)Suggest the type of substance added to promote smooth boiling in step 3.[1]
3. (b)As the reaction proceeds in step 4, the indicator changes colour. Table 2.1 shows the colours of three different indicators at pH 1.0 and at pH 14.0 and the pH range over which the indicators change colour. Table 2.1 indicator | colour at pH 1.0 | pH range over which it changes colour | colour at pH 14.0 thymolphthalein | colourless | 9.5−10.5 | blue methyl orange | red | 3.0−4.5 | yellow bromocresol green | yellow | 4.0−5.5 | blue Use the table to identify a suitable indicator. Explain your choice. indicator explanation[2]
4. (c)In step 6, a small sample of the reaction mixture is analysed along with samples of ester X and ethanoic acid. [Figure 2.2] shows the chromatogram produced. State what feature of the chromatogram shows that the hydrolysis is incomplete.[1]
5. (d)Suggest an experimental process that could be used to extract the alcohol, ROH, from the reaction mixture.[1]
6. (e)[Figure 2.3] shows an infrared spectrum of the ROH extracted in (d). Table 2.2 bond | functional groups containing the bond | characteristic infrared absorption range (in wavenumbers)/cm⁻¹ C−O | hydroxy, ester | 1040−1300 C=C | aromatic compound, alkene | 1500−1680 C=O | amide, carbonyl, carboxyl, ester | 1640−1690, 1670−1740, 1710−1750 C≡N | nitrile | 2200−2250 C−H | alkane | 2850−2950 N−H | amine, amide | 3300−3500 O−H | carboxyl, hydroxy | 2500−3000, 3200−3650 Use Table 2.2 to explain how the infrared spectrum in Fig. 2.3 shows that the ROH extracted does not contain any ester X.[1]
7. (f)[Figure 2.4] shows the proton (¹H) NMR spectrum of compound ROH. Table 2.3 shows some relevant (¹H) NMR information. Use Table 2.3 to complete Table 2.4, and state the name of ROH. Table 2.3 environment of proton | example | chemical shift range δ/ppm alkane | -CH3, -CH2-, >CH– | 0.9–1.7 alkyl next to C=O | CH3-C=O, -CH2–C=O, >CH–C=O | 2.2–3.0 alkyl next to aromatic ring | CH3-Ar, -CH2-Ar, >CH-Ar | 2.3–3.0 alkyl next to electronegative atom | CH3-O, -CH2-O, –CH2–Cl | 3.2–4.0 attached to alkene | =CHR | 4.5–6.0 attached to aromatic ring | H-Ar | 6.0–9.0 aldehyde | HCOR | 9.3–10.5 alcohol | ROH | 0.5–6.0 phenol | Ar-OH | 4.5–7.0 carboxylic acid | RCOOH | 9.0–13.0 Table 2.4 chemical shift δ/ppm | splitting pattern | relative peak area | structure responsible for the peak 1.2 | doublet | 6 | -CH3 | | 1 | | multiplet | 1 | Name of ROH[3]
8. (g)Draw the displayed formula for ester X.[2]
9. (h)Ester X will undergo hydrolysis with water in the presence of H2SO4(aq) under reflux, using a similar procedure. Suggest why none of the indicators in Table 2.1 would change colour in this experiment.[1]

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.