Edexcel Jan 2014 (IAL) Paper 4 Q16 (with explained solutions) |

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Edexcel Jan 2014 (IAL) Paper 4 Q16

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SECTION B Answer ALL the questions. Write your answers in the spaces provided. 16 This question is about the reaction scheme below which may be used to convert propanoic acid to ethyl butanoate in five steps. CH3CH2COOH Step 1 CH3CH2CH2OH Step 2 CH3CH2CH2Cl Step 3 Butanenitrile Step 4 CH3CH2CH2COOH Step 5 CH3CH2CH2COOCH2CH3 (a) Give the structural formula for butanenitrile, showing any multiple bonds. (1)*P44451A0924* Turn over<br />
(b) Give the formula of the reagent needed for each of the Steps 1, 2, 4 and 5. The reagent for Step 3 has been given. Conditions and solvents are not required. (4) Step 1Step 2KCN Step 3Step 4Step 5(c) Write the equation for the neutralization of sodium carbonate by butanoic acid. State symbols are not required. (d) State two differences between the low resolution proton nuclear magnetic resonance spectra of butan-1-ol and butanoic acid. (2) (2)(e) Give two differences between the infrared spectra of butan-1-ol and butanoic acid, mentioning any bonds involved with their wavenumber ranges. (2)10 *P44451A01024*<br />
(f) Give the skeletal formula of ethyl butanoate, CH3CH2CH2COOCH2CH3. (g) Suggest the reagents required for a different, two-step method which could be used instead of the single step method you have given for Step 5 in part (b), to obtain ethyl butanoate from butanoic acid. What is the advantage of using this alternative method? (1) (3) Reagent for first stepReagent for second stepAdvantage(Total for Question 16 = 15 marks) *P44451A01124* 11 Turn over<br />
BLANK PAGE 12 *P44451A01224*<br />

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Section B Question Number 16(a) CH3CH2CH2CN ALLOW displayed formula Acceptable Answers Acceptable Answers Reject CH3CH2CH2CN molecular formula Mark Reject Mark IGNORE conditions and solvents, even if incorrect Step 1 LiAlH4 IGNORE dry ether/ followed by H2O ALLOW lithium tetrahydridoaluminate((III)) lithium aluminium hydride (1) Step 2 PCl5 ALLOW phosphorus(V) chloride/ phosphorus pentachloride HCl /(concentrated) hydrochloric acid PCl3 / phosphorus(III) chloride/ phosphorus trichloride SOCl2 / thionyl chloride (1) Step 4 HCl/ HCl(aq)/ HCl in water or H2O ALLOW any strong acid/ H+/ NaOH/ sodium hydroxide followed by HCl / hydrochloric acid (1) Step 5 CH3CH2OH/ C2H5OH (and any strong acid) ALLOW ethanol (1) incorrect formulae, including subscripts written as large numbers or superscripts eg LiAlH4/LiAlH4 any charges NaBH4 H2/ hydrogen dilute hydrochloric acid just dilute acid just concentrated acid just H2O/ water OHCH2CH3 Question Number 16(b)<br />
Acceptable Answers Reject Mark 2CH3CH2CH2COOH + Na2CO32CH3CH2CH2COO(-)Na(+) + CO2 + H2O ALLOW butanoic acid as CH3CH2CH2CO2H/ CH3(CH2)2 COOH/CH3(CH2)2CO2H/ C3H7COOH/C3H7CO2H and the salt as CH3CH2CH2CO2H / CH3(CH2)2 COO(-)Na(+) / CH3(CH2)2CO2 C3H7COO(-)Na(+)/ C3H7CO2 all product formulae correct (1) correct balanced equation (1) ALLOW correct ionic equation for (1) 2CH3CH2CH2COOH + CO3 2CH3CH2CH2COO- + CO2 + H2O IGNORE state symbols even if incorrect (-)Na(+) / (-)Na(+) 2-Question Number 16(c)<br />
Acceptable Answers Reject Mark incorrect numbers of peaks quoted different number of peaks area under peaks in the ratio 8:10 incorrect data quoted incorrect data quoted Any two correct points from: First point butanoic acid has 4 peaks, butan-1-ol has 5 peaks OR butanoic acid has one peak fewer OR butan-1-ol has one peak more ALLOW butanoic acid has fewer peaks/ butan-1-ol has more peaks (1) IGNORE butanoic acid has 4 proton environments and butan-1-ol has 5 Second point ratio of peak heights/ area under each peak is 3:2:2:1 for butanoic acid and 3:2:2:2:1 for butan-1-ol (1) Third point the OH (hydrogens) have different chemical shifts OR butanoic acid has a (COOH) peak at 10-12 (ppm) (and butan-1-ol does not) OR butan-1-ol has (an OH) peak at 2-4 (ppm) (and butanoic acid does not) (1) Fourth point peak at 3.0-1.8 (ppm) for H-C-C=O in acid and not in the alcohol OR peak at 3.0-4.4 (ppm) for H-C-O- in alcohol and not in acid OR the hydrogens on the alpha carbon have different chemical shifts (1) IGNORE reference to splitting patterns Question Number 16(d)<br />
Acceptable Answers Reject Mark Question Number 16(e) Mark COOH/ incorrect name of bond/ 17401720 (cm-1)/ other incorrect range incorrect name of bonds First markbond and range C=O(stretching) in butanoic acid (has an absorption at) 17251700 (cm-1) (1) Second markbond and both ranges O-H/ OH (stretching) in butan-1-ol 37503200 (cm-1 ) and O-H/ OH (stretching) in butanoic acid 33002500 (cm-1) ALLOW COOH in butanoic acid (1) ALLOW any wavenumber or range of wavenumbers within the ranges above and ranges written in reverse order If no other marks are awarded, then ALLOW 1 mark if all 3 ranges are identified but bonds are missing/incorrect IGNORE reference to fingerprint region Question Number 16(f) Acceptable Answers Reject IGNORE bond lengths and bond angles ALLOW any orientation<br />
First stepPCl5/ phosphorus(V) chloride/ phosphorus pentachloride ALLOW PCl3 / phosphorus(III) chloride/ phosphorus trichloride SOCl2 / thionyl chloride (1) Second stepconditional on first mark CH3CH2OH/ C2H5OH/ ethanol (1) Advantage - stand alone mark higher yield (of ester) OR reaction goes to completion/ not an equilibrium reaction/ not reversible OR no heat energy needed/ reacts at room temperature/ no (concentrated acid) catalyst needed (1) IGNORE atom economy/ faster/ requires less energy HCl Total for Question 16 = 15 marks Question Number 16(g) Acceptable Answers Reject Mark<br />

Question 16 17 18 19

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