Edexcel Jan 2012 Paper 4 Q19

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PMT 19 The carboxylic acid, propanoic acid, can be prepared by oxidation of the alcohol, propan-1-ol. OH oxidizing agent acid OH propan-1-ol propanoic acid (a) (i) Identify a suitable oxidizing agent you could use in this reaction. (1)(ii) If you carried out this preparation in the laboratory, describe two measures you would take to ensure the maximum possible yield of propanoic acid is obtained. (2)(iii) Propanoic acid can be made by the hydrolysis of a nitrile. Give the structural formula of the nitrile and write an equation for this reaction. (3) Structural formulaEquation 12 *P39304A01224*<br /> PMT *(b) Propanoic acid reacts with methanol, CH3OH, to form the ester, methyl propanoate. CH3CH2COOH + CH3OH (cid:85) CH3CH2COOCH3 + H2O Even with the use of a catalyst, this reaction is quite slow and incomplete. Suggest a reagent, to replace the propanoic acid, which would form the ester at a faster rate. Suggest two reasons why your chosen reagent reacts faster. (3)(c) The structure of methyl propanoate can be investigated by using high resolution 1H nuclear magnetic resonance (nmr) spectroscopy. (i) What type of radiation interacts with 1H nuclei in nmr spectroscopy? (1)(ii) Describe what happens to 1H nuclei when they absorb this radiation. (2)(iii) Complete the table to show values for the chemical shift of the different 1H nuclei in methyl propanoate and their splitting pattern. Page 7 of the data booklet gives information about chemical shifts. (2) 1H environment (cid:38)(cid:75)(cid:72)(cid:80)(cid:76)(cid:70)(cid:68)(cid:79)(cid:3)(cid:86)(cid:75)(cid:76)(cid:73)(cid:87)(cid:15)(cid:3)(cid:303)(cid:3)(cid:18)(cid:3)(cid:83)(cid:83)(cid:80)(cid:3) Splitting pattern CH3O CH2 CH3 3.7 2.3 Singlet Triplet (Total for Question 19 = 14 marks) *P39304A01324* 13 Turn over<br />

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