F324 Mark Scheme January 2010 F324 Rings, Polymers and Analysis. Question Expected Answers Marks Additional Guidance 1 (a)

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1 F324 Rings, Polymers and Analysis Question Expected Answers Marks Additional Guidance 1 (a) ALLW Br Br + Br + Br 2 Br + Br (b) (i) White precipitate R white solid R white crystals 1 D T ALLW multiple substitution D T ALLW Br + D T ALLW colourless D T ALLW white ppt and bubbles Br Br 2 D T ALLW Br R 2,4,6-tribromophenol R tribromophenol (ii) 1,2-Dibromocyclohexane Br (iii) MUST spell delocalised/delocalized or localised/localized correctly once in the answer to obtain all 5 marks benzene electrons or π-bonds are delocalised phenol a lone or non-bonded pair of electrons on the oxygen or the group is (partially) delocalised into the ring cyclohexene electrons are localised R delocalised between two carbons benzene has a lower electron density R phenol has a higher electron density R cyclohexene has a higher electron density benzene cannot polarise or induce a dipole in Br 2 R phenol can polarise the Br 2 R cyclohexene can polarise Br 2 or the Br Br bond 1 5 ALLW 1,2dibromocyclohexane R 1-2dibromocyclohexane R 12dibromocyclohexane R cyclo-1,2-dibromohexane D T ALLW dibromocyclohexane R 6 10 Br 2 R structures ALLW diagram to show overlap of all 6 p-orbitals for delocalisation D T ALLW benzene has delocalised structure or ring ALLW diagram to show movement of lone pair into ring for phenol ALLW diagram or description of overlap of 2 adjacent p-orbitals for bonding in cyclohexene D T ALLW cyclohexene has a = double bond IGRE slip if cyclohexene is written as cyclohexane but - bonding correctly described D T ALLW charge density R electronegativity instead of electron density ALLW Br + R electrophile Br + as alternate to polarise 33

2 (c) ALLW IGRE l - ion D T ALLW if ring is connected to the triple bond in the diazonium or if diazonium has a negative charge ALLW one mark for correct displayed diazonium if alkyl group is not shown ALLW ALLW ALLW EF on incorrect amine for both marks for one mark 3 ALLW ALLW l and temp < 10 o R a 2 + l and temp < 10 o alkaline AD phenol (if temperature stated must be below 10 o ) Total 14 for one mark for one mark ALLW a R K & 6 5 R phenoxide ion R 6 5 ALLW reagents and conditions from the equations 34

3 Question Expected Answers Marks Additional Guidance 2 (a) (i) silver mirror 1 ALLW Ag(s) R Ag mirror R precipitate R ppt R solid ALLW brown R black R grey (b) (ii) 2 1 ALLW 2 R 2 2 R 2 2 R displayed R skeletal formula R 2 - D T ALLW 2 4 R 2-hydroxyethanoic acid 2 + 3[] + 2 reagents both products 2 ALLW displayed/skeletal formula/ if molecular formula used [] max = 1 Any correctly balanced equation for partial oxidation can score 1 mark 2 + [] 2 R 2 + 2[] + 2 R 2 + [] + 2 R 2 + 2[] + 2 (c) (i) ALLW ( 2 ) 2 R ( 2 ) 2 R skeletal formula R displayed formula D T ALLW molecular formula ( ) (ii) curly arrow from - to + dipoles and curly arrow from = bond to intermediate curly arrow from intermediate to + in 2 / + and if 2 is used it must show the curly arrow from the bond to the lone pairs are not essential 4 ALLW curly arrow to even if dipole missing or incorrect ALLW maximum of 3 marks if incorrect starting material is used See page 36 for detailed mechanisms Alternative 3 scores all 4 marks even though the intermediate is not shown 35

4 Alternative Alternative products are not required Alternative or Total 9 36

5 Question Expected Answers Marks Additional Guidance 3 (a) (i) adsorption ALLW partition R adsorbtion IGRE solubility R desorption 1 D T ALLW absorption (b) (ii) measure how far each spot travels relative to the solvent front or calculate the R f value compare R f values to those for known amino acids (iii) (amino acids won't separate because) similar compounds have similar R f (values) (i) 2 R (ii) must attempt 3D use RE symbol in the "tools" to denote whether or not each chiral is a reflection of the one given in the question 2 RE RE RE both chiral s top chiral only bottom chiral only are mirror images is a mirror image is a mirror image RE ALLW compare R f values to database ALLW compare to known amino acids D T ALLW retention times for first mark, but the 2nd mark would be available as EF ALLW alternative approach: on the same plate compare position of spots with known amino acids 1 ALLW spots often overlap R don t (fully) separate ALLW they have similar R f (values) or similar adsoptions or similar retention times EF to a(ii) ALLW R( 2 ) any order for R, 2 and but must be next to must be shown 1 ALLW 2 brackets around 2 are not essential ALLW structure 3 each chiral must have 2 bonds, 1 wedge bond (IGRE shading) & 1 dash bond (IGRE wedge) check the clockwise orientation of each. For each start with the and if on the: top the is followed by it is not a mirror image. If it is a mirror image annotate using RE. bottom the is followed by 3 it is not a mirror image. If it is a mirror image annotate using RE. the four groups can be attached in any order. If the molecule is drawn upside down clockwise becomes anti-clockwise. MUST check that the drawn structure is non-superimposable irrespective of the orientation or the way it has been drawn. IGRE bond linkage for all groups 37

6 (c) ALLW ALLW ( 2 ) 2 ( 2 ) 4 If 3 fully displayed ALLW + charge on or - alanine at p = 6.0 glutamic acid at p =10 lysine at p = 2.0 (d) valine glycine leucine (e) 2 ( 2 ) 6 2 ( 2 ) If fully displayed ALLW charge on only ALLW val gly leu D T ALLW structures 1 2 ALLW ALLW ALLW 2 for ALLW acid chloride, l( 2 ) 8 l ALLW displayed formulae or skeletal formulae Total 14 38

7 Question Expected Answers Marks Additional Guidance 4 (a) infrared 1 mark only shows (very broad) peak between (cm 1 ) (due to bond) ALLW (very broad) peak around 3000 (cm 1 ) R any stated value between 2500 and 3300 (cm 1 ) for D T ALLW peak in range (cm 1 ) 3 IGRE any reference to = or as both are also present in an ester R to fingerprint region 13 MR 2 marks ( 3 ) 2 2 has 4 peaks (due to 4 different environments) ( 3 ) 3 has 3 peaks (due to 3 different environments) (b) splitting pattern explains any two in terms of n + 1 rule for two marks Explains any one peak for 1 mark 6 ALLW 13 MR detects the number of/different environments for 1, suitable example for the 2nd mark 1 mark for correct ester if two splitting patterns are correctly analysed ignore the third singlet therefore adjacent (if any) has no s multiplet R split into 7 therefore adjacent s have lots of/6 s doublet therefore adjacent is bonded to 1 ALLW singlet because next or bonded to an ALLW multiplet/heptet because next to 2 3 s ALLW doublet because next to a must spell one of multiplet / heptet, singlet, doublet correctly max = 2 marks chemical shifts ALLW tolerance on values; , and

8 two marks if any two absorptions are identified (ppm) correctly one mark if any one absorption is identified correctly ALLW any two gets 2 marks, any one scores 1 mark peak ~3.7 (ppm) bonded to an R peak ~2.7 (ppm) indicates it is next to a = 3.7 (ppm) 2.7 (ppm) 1.2 (ppm) peak ~1.2 (ppm) bonded to other s R part of a chain max = 2 marks ALLW peaks labelled on the spectrum ALLW singlet must be bonded to, multiplet to = and doublet to or R for both chemical shift marks if two chemical shifts are correctly identified IGRE the third compound identified as ( 3 ) marks compound identified as 3 ( 3 ) 2 1 mark Total 9 40

9 Question Expected Answers Marks Additional Guidance 5 (a) ALLW 2 or 1 D T ALLW incorrect bond linkage or or (b) (i) equation ( 3 ) ALLW ( 3 ) reactants ALLW products 2 D T ALLW molecular formulae 41

10 (ii) is ALLW amide shown as either 3 R 3 R 3 R ALLW ester shown as either 3 R 3 3 or 3 3 (iii) to ensure that there are no (harmful) side effects 1 ALLW impurities reduce effectiveness (of drug) R might be toxic R avoids litigation R harmful R hazardous ALLW to ensure that the drug/active component is safe IGRE dangerous R nasty R can kill R increased dosage (c) (aspirin contains) ester AD carboxylic acid 2 IGRE arene or benzene or aromatic or phenyl or methyl but any other group loses the mark ALLW carboxyl group D T ALLW acid ( paracetamol contains) amide AD phenol IGRE arene or benzene or aromatic or phenyl or methyl but any other group loses the mark ALLW peptide ALLW hydroxy(l) D T ALLW hydroxide or alcohol D T ALLW amine (d) (i) Both 3 ALLW hydrolysis by + (aq) or + or l(aq) or l or 2 S 4 (aq) 42

11 a R a or 2 S 4 to give hydroxybenzoic acid + ethanoic acid with aspirin - and ammonium salt of 4-aminophenol + ethanoic acid with (a + ) paracetamol 3 ALLW hydrolysis by (aq) or a(aq) and other alkali leading to hydrolysis to give carboxylate salt and phenoxide salt on the ring + ethanoate with aspirin and 4-aminophenoxide ion + ethanoate ion with paracetamol from aspirin ALLW 3 (and 2S 4) to give 2 in one or more positions on the ring in both aspirin and paracetamol 3 D T ALLW 3 but correct ammonium salts can be awarded 2 marks EF from paracetamol - (a + ) D T ALLW 2 but correct products can be awarded 2 marks EF if no reagent there cannot be any marks for the products If reagent selected is incorrect but would react with either aspirin or paracetamol ALLW EF for the correct organic product (ii) aspirin only a 3 R a 2 3 R metal oxide - (a + ) 3 2 ALLW Mg, carbonates, 3 ALLW alcohols (R) to give ester if no reagent there cannot be any marks for the products 3 R If reagent selected is incorrect but would react with BT aspirin and paracetamol ALLW EF for the correct organic product (iii) paracetamol only ALLW Br 2 water 43

12 ALLW one or more Br at any position on the ring Br 2 D T ALLW Br substitution of ALLW acyl chloride or acid anhydride and corresponding ester 3 ALLW Fel 3 to form a purple complex ion (structure not required) 2 ALLW diazonium and structure showing azo group substituting one of the s in the ring if no reagent there cannot be any marks for the products Br If reagent selected is incorrect but would react with BT aspirin and paracetamol ALLW EF for the correct organic product Total 14 44

13 Grade Thresholds Advanced GE hemistry A (034/434) January 2010 Examination Series Unit Threshold Marks F321 F322 F324 Unit Maximum a b c d e u Mark Raw UMS Raw UMS Raw UMS Specification Aggregation Results verall threshold marks in UMS (i.e. after conversion of raw marks to uniform marks) Maximum A B D E U Mark The cumulative percentage of candidates awarded each grade was as follows: A B D E U Total umber of andidates candidates aggregated this series. For a description of how UMS marks are calculated see: Statistics are correct at the time of publication. 45

14 R (xford ambridge and RSA Examinations) 1 ills Road ambridge B1 2EU R ustomer ontact entre Qualifications (General) Telephone: Facsimile: general.qualifications@ocr.org.uk For staff training purposes and as part of our quality assurance programme your call may be recorded or monitored xford ambridge and RSA Examinations is a ompany Limited by Guarantee Registered in England Registered ffice; 1 ills Road, ambridge, B1 2EU Registered ompany umber: R is an exempt harity R (xford ambridge and RSA Examinations) ead office Telephone: Facsimile: R 2010

1 (a) (CH 3 CO) 2 O + CH 3 CH(OH)CH 3 CH 3 COOCH(CH 3 ) 2 + CH 3 COOH

1 (a) (CH 3 CO) 2 O + CH 3 CH(OH)CH 3 CH 3 COOCH(CH 3 ) 2 + CH 3 COOH Question er Mark Guidance 1 (a) ( 3 ) 2 + 3 () 3 3 ( 3 ) 2 + 3 1st mark orrect structure of ester: 3 ( 3 ) 2 2nd mark Equation contains correct formulae for ( 3 ) 2, 3 () 3 AND 3 2 ALLW correct structural