Edexcel Jun 2016 Paper 4 Q15

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SECTION C Answer ALL the questions. Write your answers in the spaces provided. 15 Salicylic acid is the active ingredient in one method of treatment of verrucas, warts and acne. The structure of salicylic acid is shown below. OH OH A laboratory method of preparing salicylic acid is the hydrolysis of the ester, methyl salicylate, which is present in Oil of Wintergreen. A sample of the ester is initially refluxed with sodium hydroxide and salicylic acid is then precipitated by adding a strong acid. (a) (i) Complete the equation for the alkaline hydrolysis of the ester group in methyl salicylate, using sodium hydroxide. OH + NaOH (cid:108)(cid:1)(ii) The salicylic acid is precipitated out of solution by the addition of dilute sulfuric acid until it is in excess. How could you tell that the sulfuric acid is in excess? (1) (1)(b) Salicylic acid is sparingly soluble in water. Explain this observation in terms of intermolecular forces. (2)A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D *P46660RA02328* 23 Turn over<br /> (c) State three ways in which the acid hydrolysis of an ester differs from the alkaline hydrolysis of an ester. (3)D O N O T W R I T E I N T H I S A R E AD O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A 24 *P46660RA02428*<br /> (d) Salicylic acid can undergo various reactions as outlined below. (i) Give the formula of the reagents A and B and the skeletal formula of the product C. (3) OH OH ABOH Cl OH C2H5OH OH A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D (ii) Both compound D and salicylic acid react with ethanol. State two differences between these reactions. (2) A E R A S I H T N I E T I R W T O N O D*P46660RA02528* 25 Turn over<br /> *(e) Use chemical shift data from the Data Booklet to sketch the high resolution proton nmr spectrum for ethanol. The peaks do not overlap. Explain the number of peaks, their splitting pattern and the ratio of the areas under each set of peaks. (5) 10 Chemical shift, (cid:303) / ppm26 *P46660RA02628* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D (f) Tetramethylsilane, Si(CH3)4, is used as a reference standard in nmr spectra. Suggest why it gives a very strong signal in the spectrum. (1)(g) State the type of radiation that is used to create the nmr spectrum. (1)(h) Use the Data Booklet to state two differences between the infrared spectra of salicylic acid and compound D. Include the wave numbers of the relevant groups or bonds. (2)(Total for Question 15 = 21 marks) TOTAL FOR SECTION C = 21 MARKS TOTAL FOR PAPER = 90 MARKS A E R A S I H T N I E T I R W T O N O D *P46660RA02728* 27<br />

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