Edexcel Jun 2013 (R) Paper 4 Q12

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12 This question is about the reactions of butanoic acid, CH3CH2CH2COOH. It has a foul smell and behaves like a typical carboxylic acid. (a) (i) The addition of sodium carbonate solution is often used as a chemical test to distinguish carboxylic acids, like butanoic acid, from other compounds, such as aldehydes. Explain why old stocks of aldehydes often react with sodium carbonate solution. (1)(ii) How would the result of this test distinguish between a carboxylic acid and an old stock of an aldehyde? (1)(iii) Write the balanced chemical equation, including state symbols, for the reaction of sodium carbonate solution with butanoic acid. *(iv) Infrared spectroscopy is a good physical method to distinguish carboxylic acids from other organic compounds. Give the wavenumbers of two characteristic absorptions for a carboxylic acid. Indicate the bond responsible for each absorption. Suggest why one of the absorptions is broad. (2) (3)14 *P42984A01424*<br /> (v) High resolution nuclear magnetic resonance spectroscopy is a suitable physical method to use alongside infrared spectroscopy to identify butanoic acid. State the total number of peaks and suggest the splitting pattern for each peak that you would expect for butanoic acid, CH3CH2CH2COOH. (3)(b) Sketch the titration curve obtained when 50 cm3 of 0.10 mol dm3 sodium hydroxide solution is added to 25 cm3 of 0.10 mol dm3 butanoic acid. (4) pH 141210864210 20 30 40 50 Volume of NaOH(aq)/cm3 *P42984A01524* 15 Turn over<br /> (c) (i) What would you see when phosphorus pentachloride, PCl5, reacts with butanoic acid? (1)(ii) Give the structural formula and name of the organic product of this reaction. (2) Structural formula Name(d) (i) Give the name or formula of the organic product of the reaction between butanoic acid and lithium tetrahydridoaluminate (lithium aluminium hydride). (1)(ii) Water cannot be used as the solvent in this reaction because it reacts with lithium tetrahydridoaluminate. Suggest a suitable solvent. (1)(iii) State the type of reaction that takes place between butanoic acid and lithium tetrahydridoaluminate. Justify your classification. (2) TypeJustification16 *P42984A01624*<br /> (e) (i) Butanoic acid can be reacted with methanol to make methyl butanoate. State two conditions that help to speed up this reaction. (2)(ii) Draw the displayed formula of methyl butanoate. (iii) Identify another chemical, by name or formula, which could be added to methanol to make methyl butanoate. (1) (1)*(iv) Give two advantages and one disadvantage of using the reaction occurring in (e)(iii), compared to the reaction in (e)(i), when making methyl butanoate. (3) AdvantagesDisadvantage(Total for Question 12 = 28 marks) TOTAL FOR SECTION B = 49 MARKS) *P42984A01724* 17 Turn over<br /> BLANK PAGE 18 *P42984A01824*<br />

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