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GCE

Oxford Cambridge and RSA Examinations

Unit F324: Rings, Polymers and Analysis

Advanced GCE

Chemistry A

Mark Scheme for June 2011

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This mark scheme is published as an aid to teachers and students, to indicate the requirements ofthe examination. It shows the basis on which marks were awarded by Examiners. It does notindicate the details of the discussions which took place at an Examiners meeting before markingcommenced.

All Examiners are instructed that alternative correct answers and unexpected approaches incandidates scripts must be given marks that fairly reflect the relevant knowledge and skillsdemonstrated.

Mark schemes should be read in conjunction with the published question papers and the Report onthe Examination.

OCR will not enter into any discussion or correspondence in connection with this mark scheme.

OCR 2011

Any enquiries about publications should be addressed to:

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F324 Mark Scheme

ALLOW Kekul structures throughoutQuestion Answer Mark Guidance

1 (a) AlCl3 + Cl2 AlCl4 + Cl+

+

ClH

Cl

Cl+

H++

curly arrow

from -bond

to Cl+

correct intermediate

curly arrow from

CH bond back to

reform -ring

correctproducts

H+ + AlCl4 AlCl3 + HCl

Note: 1st curly arrow should start within the ring or on the ring

---------------------------------------------------------------------------------------Note: ALLOW mechanism using Kekul structures:

+

ClHClCl+

H++

6

ANNOTATIONS M

DO NOT ALLOW

+

ClH

-ritha

AN

'ho

way

ieg

ALLOW + sign anintermediate

ALLOW 1st curly

ALLOW mechanisie

Cl Cl

Second curly arrow

Note: If Br+

is usedmark but all other

1

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F324 Mark Scheme

Question Answer Mark Guidance1 (b) (i)

Cl3CCHO2 +

Cl

+ H2O 1st mark: reactants, correctly balanced,ie 2 C6H5Cl + Cl3CCHO

2nd mark: product, (correctly balanced)ie H2O

2

Each mark is ind

ALLOW C6H5Cl fo

ALLOW any uname.g. CCl3CHOBUT .. DO NOT

Standalone mark

Standalone mark

(ii) 6 1(c) substitution/nitration/NO2 at different positions (on the ring)

ORforms different isomers

ORmultiple substitution/nitration 1

ALLOW examples1-chloro-2-nitrobeALLOW it for nitr

ALLOW examplesIGNORE nitrate/N

(d)In phenol,

(lone) pair of electrons on O is (partially) delocalised intothe ring QWC: delocalised/delocalized/delocalise, etc must be speltcorrectly in the correct context for benzene OR phenol atleast once

electron density increases/is high ORA

Cl2/electrophile is (more) polarised ORA 3

ANNOTATIONS M

ALLOW diagram tring but delocalisALLOW lone pair attracted/pulled intIGNORE activate

DO NOT ALLOW

ALLOW Cl2 is (moOR Cl2 is not polaOR induces dipole

Total 13

2

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F324 Mark Scheme

Question Answer Mark Guidance

2 (a) (i) donates a lone pair (on N)ORaccepts a proton/H+ 1

IGNORE forms a dative(no direction of lone paiALLOWforms a dative

ALLOW mark for N:H

(ii) (C2H5NH3+

)2SO42

C2H5NH3+ CH3COO

2

ALLOW (C2H5NH3)2 SODO NOT ALLOW (C2H5brackets not required

ALLOW (C2H5NH3)(CH

brackets not requiredALLOW separate ions wthem, e.g. C2H5NH3

+ +

(b) (i)

N N+

COOH

OH

diazonium ion compound B

2

In diazonium ion, IGNOALLOW + sign up to h

N

In compound B,ALLOW OH ionised asALLOW COOH ionise

(ii)

conditions = alkaline /OH

AND

use = dye/pigment/colouring

1

BOTH responses requi

ALLOW named alkali, e

ALLOW base

IGNORE references to t

ALLOW use = indicator

3

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F324 Mark Scheme


2 (b) (iii) Organic product:

Other products: CO2AND H2O 2

IGNORE phenoxide: O

ALLOW COOOR COO

ALLOW H2CO3Note: must be formulae

(c)

+ H2ON N+

OH + N2 + H+

1

ALLOW N2+ on structur

ALLOW C6H5N2+ + H2O

ALLOW C6H5N2Cl + H2

If + charge shown, IGNO

Total 9

4

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F324 Mark Scheme


3 (a) monomers join/bond/add/react/form polymer/form chainAND another product/small molecule e.g. H2O/HCl

QWC must spell AND use monomer(s) correctlythroughout

1

IGNORE two when refie (two) monomers

(b) (i)

ester link Note: Any ester link shown must be correct

rest of the structure

2

ALLOW correct structuOR mixture of the above

ALLOW benzene ring f

End bonds MUST be s

ALLOW one or more renumber of repeat units

For ester, DO NOT ALL

ALLOW structure with n

IGNORE bracketsIGNOREn

(ii)

1


ALLOW one or more renumber of repeat units

End bonds MUST be s

IGNORE bracketsIGNOREn

5

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F324 Mark Scheme


3 (c) compound C

compound D andcompound E

3

ALLOW correct structuOR mixture of the abovALLOW CH2C(CH3)CO

ALLOW D and E by Eprovided that C containformulae of D and E isbond

(d) (i)

1

ALLOW correct structuOR mixture of the abov

e.g. (CH3)2CHOH

DO NOT ALLOW HO

IGNORE working (ieostructure of propan-2-o

IGNORE name (even

6

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F324 Mark Scheme


3 (d) (ii)

OH

O

OR acid anhydride:

O

O O

1

ALLOW correct structuOR mixture of the abovOR (2-)methylpropano

DO NOT ALLOW inco

(will CON a correct str

ALLOW acyl chloride:

IGNORE working provshown

(iii)

Hydrogen bonds form with water Note: Can be shown in diagram as dashed line,ie---- (no label required)

DO NOT CON hydrogen bond from an incorrect hydrogenbond in diagram

Mandelic acid forms more hydrogen bonds (with water) ORA

Mandelic acid has an extra OHOR 2 OH groupsOR has a COOH group ORA

3

ANNOTATIONS MUS

ALLOW a diagram shodipole and lone pair arALLOW a hydrogen bIGNORE bond angles

Diagram does not nee(IGNORE if wrong)

ALLOW any comparisprovided that mandelic

DO NOT ALLOW No DO NOT ALLOW refe

IGNORE reference to forces

Note: If a response cothan with mandelic aci1st mark hydroge2nd mark Ester 2

OR Es

7

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F324 Mark Scheme


3 (d) (iv) To test for (adverse) side effectsOR to test toxicityOR to test for irritation 1

ALLOW a stated adversegallergy, carcinogenic

IGNORE references to

IGNORE vague statemedangerous to skin, corro

ALLOW company liable

Total 13

8

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F324 Mark Scheme


4

Equations

CH3COCHO + 4[H] CH3CHOHCH2OH

CH3COCHO + [O] CH3COCOOH

Reduction reagents and observationMethylglyoxal is reduced by NaBH4

Oxidation reagents and observationMethylglyoxal is oxidised by H2SO4AND K2Cr2O7

Observation: turns green OR blue

ORMethylglyoxal is oxidised by Tollens reagent

Observation: Silver (mirror)

1

1

1

2

ANNOTATIONS MUSTThroughout question,AOR skeletal formulaDO NOT ALLOW molec

ALLOW partial reductio[H] implies reduction[O] implies oxidation

reduced AND reagent aALLOW link to equationALLOW LiAlH4 as alternALLOW any recognisabIGNORE any reference

oxidised AND reagent aALLOW link to equation

ALLOW Na2Cr2O7 insteALLOW H+AND Cr2O7

2

If name given, ALLOWALLOW acidified dichroALLOW any strong acidIf formulae used, formul

ALLOW AgNO3 in amm

ALLOWoxidised by mObservation: decolouris

Note: If one reaction is other is reduction (and v

Total 5

9

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F324 Mark Scheme


5 (a) idea of separating (the components/compounds)

idea of (identifying compounds) by comparison with a(spectral) database

2

ALLOW (identifies com(patterns)/fragment ions

Note: Each marking poior MS (The question astechnique)

(b) (i) 54.2% of 118 OR 54.2/118 x 100 = 64/63.96(hence there are 4 oxygens)

118 64 = 54 hence 4 carbon (48) and 6 hydrogen (6) 2

IGNORE calculation thamass of 118 (ie 12 x 4 +ALLOW 64/118 x 100 =IGNORE method using

ALLOW any reasonable

Note: 54.2(%) 16 wou

could be used to get the

(ii) carboxyl group OR carboxylic acid must be name (in question)

1 IGNORE working, e.g. O

10

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F324 Mark Scheme


5 (c) (i)

Chemical shiftsAny two peaks identified for 1 mark

peak at = 0.8 ppm due to RCH/ CH3CH

peak at = 3.4 ppm due to HCC=Opeak at = 11 ppm due to COOH/ carboxylic acid

Splittingquartet shows adjacent CH3OR 3 adjacent Hs

doublet shows adjacent CH OR 1 adjacent H

Identification

HO C

O

CH C

O

OH

CH3

1

2

1

ANNOTATIONS MUST CHECK SPECTRUM foANNOTATE with ^

For peak at ( =) 0.8 (p

For peak at (

=) 3.4 (pFor peak at ( =) 11 (pp

ALLOW peak at = 2.4ALLOW tolerance on

For quartet, ALLOW qu


(ii) (CD3)2SO / D / It does not absorbOR does not give a peak

1 ALLOW (CD3)2SO / doeALLOW undeuterated s

ALLOW responses in te butIGNORE

(iii) TMS is the standard (for chemical shift measurements) 1 ALLOW TMS is the refefor calibration

IGNORE unreactive, vo

(iv) peak at = 11.0 (ppm) disappears 1 ALLOW COOH (peak)

ALLOW OH (peak) disaTotal 12

11

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F324 Mark Scheme


6 (a) (i)

CCH

NC

H

CH

O

H2N OCH3

H2C

OCH2HOOC 1

Circles can be around Cother atoms

ALLOW any suitable waasterisk, *

Note: Mark the circles a

(ii) carboxyl OR carboxylic acid, amine, amide, estermust be names

2 marks for 4 correct functional groups 1 mark for 3 correct functional groups 2

ALLOW peptide for ami

(b)

1 mark for left-hand amino acid with NH3+OR NH2

1 mark for right-hand amino acid with NH3+OR NH2

1 mark for both amino acids shown with NH3+

4

ALLOW correct structurOR mixture of the above

ALLOW + charge on H

Note: If there are more tcorrect structures and ig

12

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F324 Mark Scheme

13


6 (c) (adverse) side effectsOR toxicityOR irritation 1

ALLOW a stated advershyperactivity etc

IGNORE references to o

IGNORE vague statemedangerous to body

DO NOT ALLOW obesi

ALLOW company liable

Note: Scroll down to botwriting

Total 8

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