Edexcel Jun 2017 (IAL) Paper 6 Q2 (with explained solutions) |

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Edexcel Jun 2017 (IAL) Paper 6 Q2

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2 This question is about the three isomeric carbonyl compounds shown in the table. pentanal pentan-2-one pentan-3-one (a) (i) Each of these compounds was subjected to three chemical tests. Complete the table below to show the observation for each test. If appropriate, write no change. (5) Observations pentanal pentan-2-one pentan-3-one Test 2,4-dinitro- phenylhydrazine Tollens reagent Iodoform test *P48386A0516* Turn over<br />
(ii) Name the reagents that are required for the iodoform test, and describe the procedure for carrying out this test. (3)(b) On the structures in the table below, circle the proton environments in each molecule that would produce a peak in its nmr spectrum, indicating clearly if any of these environments are identical. Hence give the number of different proton environments in each molecule. (3) Structure Number of different proton environments (Total for Question 2 = 11 marks) *P48386A0616*<br />
BLANK PAGE *P48386A0716* Turn over<br />

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Questio Number 2(a)(i) Mar k (5) Acceptable Answer Reject Observations pentanal pentan- 2-one pentan- 3-one red / orange / yellow ppt red / orange / yellow ppt red / orange / yellow ppt Test 2,4- dinitro- phenyl- hydrazin Tollens reagent silver mirror / black ppt / no change no change grey ppt no change (pale) yellow ppt OR antiseptic smell no change Iodofor m test solution for ppt orange ppt 2,4-DNPH tests all three correct scores 2 ALLOW two correct scores 1 three precipitates but no / incorrect colour scores 1 three solutions scores zero (2) each other positive test scores 1 (2) Penalise omission of ppt in Tollens and iodoform tests once only Four correct no change scores 1 mark IGNORE Extra no changes (1)<br />
Acceptable Answer Reject Mark (3) Just alkali Ethanol as a solvent Reflux The two methods must be marked separately MP1 and MP2 Method 1 Iodine (solution) / I2((aq) ) / iodine in potassium iodide (solution) (1) Sodium hydroxide (solution) / NaOH((aq)) OR Potassium hydroxide (solution) / KOH((aq)) (1) MP1 and MP2 Method 2 Add potassium iodide / KI((aq)) ALLOW Add sodium iodide / NaI((aq)) (1) Add sodium chlorate((I)) / sodium hypochlorite / NaOCl((aq)) (1) MP3 MP3 is dependent on two correct reagents from a single method or on iodine and alkali in method 1 Any indication that the inorganic reagents are in (aqueous) solution including dilute OR (Method 1 only) Add alkali to iodine until (brown solution) turns colourless OR Warm OR Heat in a water bath ALLOW Just heat (1) Question Number 2(a)(ii)<br />
Question Number 2(b) Acceptable Answer Reject Mark (3) Structure Number of Proton Environments (1) (1) (1) If all three marks are not awarded All three diagrams correct with correct linked proton environments scores 2 All three diagrams correct showing proton environments only scores 1 All three numbers of proton environments correct scores 1 mark ALLOW any indication of identical environments in propan- 3-one (Total for Question 2 = 11 marks)<br />

Question 1 2 3 4

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