AQA Specimen Paper 2 Q9

Answers available below

22 1,4-diaminobenzene is an important intermediate in the production of polymers such as Kevlar and also of polyurethanes, used in making foam seating. A possible synthesis of 1,4-diaminobenzene from phenylamine is shown in Figure 8. Figure 8 NHCOCH3 NH2 Step 1 Step 2 Step 4 NH2 NH2 NHCOCH3 NO2 Step 3 NH2 NO2 0 9 . 1 A suitable reagent for step 1 is CH3COCl Name and draw a mechanism for the reaction in step 1. [5 marks] Name of mechanism Mechanism Typesetter code Barcode<br /> 23 . 2 0 9 The product of step 1 was purified by recrystallisation as follows. The crude product was dissolved in the minimum quantity of hot water and the hot solution was filtered through a hot filter funnel into a conical flask. This filtration removed any insoluble impurities. The flask was left to cool to room temperature. The crystals formed were filtered off using a Buchner funnel and a clean cork was used to compress the crystals in the funnel. A little cold water was then poured through the crystals. After a few minutes, the crystals were removed from the funnel and weighed. A small sample was then used to find the melting point. Give reasons for each of the following practical steps. The minimum quantity of hot water was used [4 marks] The flask was cooled to room temperature before the crystals were filtered off The crystals were compressed in the funnel A little cold water was poured through the crystals Question 9 continues on the next page Barcode Typesetter code Turn over <br /> 24 0 9 . 3 The melting point of the sample in Question 9.2 was found to be slightly lower than a data-book value. Suggest the most likely impurity to have caused this low value and an improvement to the method so that a more accurate value for the melting point would be obtained. [2 marks] Figure 8 is repeated here to help you answer the following questions. NH2 Figure 8 NHCOCH3 Step 1 Step 2 Step 4 NH2 NH2 NHCOCH3 NO2 Step 3 NH2 NO2 Barcode Typesetter code<br /> 25 0 9 . 4 In an experiment starting with 5.05 g of phenylamine, 4.82 g of purified product were obtained in step 1. Calculate the percentage yield in this reaction. Give your answer to the appropriate number of significant figures. [3 marks] Percentage yield = 0 9 . 5 A reagent for step 2 is a mixture of concentrated nitric acid and concentrated sulfuric acid, which react together to form a reactive intermediate. Write an equation for the reaction of this intermediate in step 2. 0 9 . 6 Name a mechanism for the reaction in step 2. . 7 0 9 Suggest the type of reaction occurring in step 3. 0 9 . 8 Identify the reagents used in step 4. [1 mark] [1 mark] [1 mark] [1 mark] Barcode Typesetter code Turn over <br />

Show answer