Many organic reactions performed in the laboratory require heating under reflux. 4-nitromethylbenzene can be converted directly to 4-aminobenzaldehyde by heating it under reflux with an excess of solution A. Solution A is an aqueous alkaline mixture of Na₂S•9H₂O and S₈. Ethanol is used as a solvent for the reaction. [Figure showing reaction scheme from 4-nitromethylbenzene to 4-aminobenzaldehyde with solution A] The apparatus for this reaction is shown in the diagram. [Figure showing reflux apparatus with reflux condenser, round-bottomed flask, tap funnel, solution A, 4-nitromethylbenzene dissolved in ethanol]

1. (a)(i)Show, using a labelled arrow, where the cooling water enters the reflux condenser.[1]
2. (a)(ii)After the complete addition of solution A to the solution in the round-bottomed flask, a vigorous exothermic reaction takes place. What should be done to control the vigorous exothermic reaction during the addition of solution A?[1]
3. (a)(iii)The mixture is heated to increase the rate of reaction. This is carried out under reflux. Other than to increase the rate of reaction, explain why a reflux process is used for heating the mixture.[1]
4. (a)(iv)A student suggests that placing a bung in the top of the condenser would improve the experiment. Comment on whether the student is correct. Explain your answer.[1]
5. (b)(i)Once the reaction is complete, the round-bottomed flask is removed from the set-up on page 2 and included in a new set-up for distillation. The distillation process separates the substances in the mixture in the flask. Complete and label the diagram to show how the apparatus could be set up for distillation. [Figure showing a round-bottomed flask][2]
6. (b)(ii)The mixture in the round-bottomed flask is heated until all of the first substance distils off. The heating is then stopped. After distillation a hot solution remains in the round-bottomed flask. The table shows some data relevant to the experiment. substance | melting point/°C | boiling point/°C ---|---|--- [Figure for 4-aminobenzaldehyde] CHO, H₂N | 72 | 138 H₂O | 0 | 100 CH₃CH₂OH | -114 | 78 Use the data to identify the liquid that is first distilled off. Explain your answer.[1]
7. (b)(iii)4-aminobenzaldehyde is soluble in hot water, but not in cold water. Starting with the hot solution in the round-bottomed flask, suggest how pure crystals of 4-aminobenzaldehyde can be obtained.[2]
8. (c)Under acidic conditions, 4-aminobenzaldehyde (C₇H₇NO) forms a solid compound with molecular formula C₁₄H₁₂N₂O. 2C₇H₇NO → C₁₄H₁₂N₂O + H₂O A student carries out two experiments according to the method on page 2 to make C₇H₇NO. In Experiment 1, the student obtains 6.00 g of solid. In Experiment 2, the student uses the same method as in Experiment 1 but adds acid to neutralise the alkali in the mixture in the flask after heating under reflux. The same quantities of reagents are used in Experiment 1 and Experiment 2. Suggest how the mass of solid obtained in Experiment 2 compares to that of Experiment 1. Explain your answer.[2]
9. (d)4-aminobenzaldehyde can be reacted with a halogenoalkane to form 4-(dimethylamino)benzaldehyde, compound D. [Figure showing reaction scheme from 4-aminobenzaldehyde + halogenoalkane to compound D] Some data is given that is relevant to this reaction. halogenoalkane | boiling point /°C | carbon-halogen bond energy /kJ mol⁻¹ ---|---|--- CH₃Cl | -97 | 340 CH₃Br | 4 | 280 CH₃I | 43 | 240 Give two reasons why CH₃I is the preferred halogenoalkane in the conversion of 4-aminobenzaldehyde to compound D.[2]

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