Organic Analysis - Identification of Functional Groups by Test-tube Reactions - Mark schemes

Q1.(a)     M1 acidified potassium dichromate or K2Cr2O7 / H2SO4

OR K2Cr2O7 / H+ OR acidified K2Cr2O7

M2 (orange to) green solution OR goes green

M3 (solution) remains orange or no reaction or no (observed) changeIf no reagent or incorrect reagent in M1, CE = 0 and no marks for M1, M2 or M3If incomplete / inaccurate attempt at reagent e.g. “dichromate” or “dichromate(IV)” or incorrect formula or no acid, penalise M1 only and mark onFor M2 ignore dichromate described as “yellow” or “red”For M3 ignore “nothing (happens)” or “no observation”

Alternative using KMnO4 / H2SO4

M1  acidified potassium manganate(VII) / potassium permanganate or       KMnO4 / H2SO4

OR KMnO4 / H+  OR acidified KMnO4

M2  colourless solution OR goes colourless

M3  (solution) remains purple or no reaction or no (observed) changeFor M1If incomplete / inaccurate attempt at reagent e.g. “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 only and mark onCredit alkaline KMnO4 for possible full marks but M2 gives brown precipitate or solution goes green

3

(b)     M1   (Shake with) Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)

M2   (stays) orange / red / yellow / brown / the same

        OR no reaction OR no (observed) change

M3   decolourised / goes colourless / loses its colour / orange to colourlessIf no reagent or incorrect reagent in M1, CE = 0 and no marks for M1, M2 or M3If incomplete / inaccurate attempt at reagent (e.g. Br), penalise M1 only and mark onNo credit for combustion observations; CE = 0For M2 in every caseIgnore “nothing (happens)”Ignore “no observation”Ignore “clear”

OR as alternatives

Use KMnO4 / H2SO4

M1 acidified potassium manganate(VII) / potassium permanganate OR      KMnO4 / H2SO4

OR KMnO4 / H+ OR acidified KMnO4

M2 (stays) purple or no reaction or no (observed) change

M3 decolourised / goes colourless / loses its colour

Use iodine

M1 iodine or I2 / KI or iodine solution

M2 no change

M3 decolourised / goes colourless / loses its colour

Use concentrated sulfuric acid

M1 concentrated H2SO4

M2 no change

M3 brownFor M1, it must be a whole reagent and / or correct formulaFor M1 penalise incorrect attempt at correct formula, but mark M2 and M3With potassium manganate(VII)If incomplete / inaccurate attempt at reagent e.g. “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 only and mark onCredit alkaline / neutral KMnO4 for possible full marks but M3 gives brown precipitate or solution goes greenApply similar guidance for errors in the formula of iodine or concentrated sulfuric acid reagent as those used for other reagents.

3

(c)     M1 Any soluble chloride including hydrochloric acid (ignore concentration)

M2 white precipitate or white solid / white suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble iodide including HI

M2 yellow precipitate or yellow solid / yellow suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble bromide including HBr

M2 cream precipitate or cream solid / cream suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 NaOH or KOH or any soluble carbonate

M2 brown precipitate or brown solid / brown suspension with NaOH / KOH      (white precipitate / solid / suspension with carbonate)

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

If no reagent or incorrect reagent or insoluble chloride in M1, CE = 0 and no marks for M1, M2 or M3Allow chlorine waterIf incomplete reagent (e.g. chloride ions) or inaccurate attempt at formula of chosen chloride, or chlorine, penalise M1 only and mark onFor M2 require the word “white” and some reference to a solid. Ignore “cloudy solution” OR “suspension” (similarly for the alternatives)For M3Ignore “nothing (happens)”Ignore “no observation”Ignore “clear” on its ownIgnore “dissolves”

3

(d)     M1 Any soluble sulfate including (dilute or aqueous) sulfuric acid

M2 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

M3 white precipitate or white solid / white suspensionIf no reagent or incorrect reagent or insoluble sulfate in M1, CE = 0 and no marks for M1, M2 or M3Accept MgSO4 and CaSO4 but not barium, lead or silver sulfatesIf concentrated sulfuric acid or incomplete reagent (e.g. sulfate ions) or inaccurate attempt at formula of chosen sulfate, penalise M1 only and mark onFor M3 (or M2 in the alternative) require the word “white” and some reference to a solid.Ignore “cloudy solution” OR “suspension”For M2 (or M3 in the alternative)Ignore “nothing (happens)”Ignore “no observation”Ignore “clear” on its ownIgnore “dissolves”

OR as an alternative

M1 NaOH or KOH

M2 white precipitate or white solid / white suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

If incomplete reagent (e.g. hydroxide ions) or inaccurate attempt at formula of chosen hydroxide, penalise M1 only and mark onIf M1 uses NH3 (dilute or concentrated) penalise M1 only and mark on

3[12]

Q2.(a)     (i)      Green

Ignore shades of green.1

(ii)     Excess acidified potassium dichromate(VI)1

Reflux (for some time)1

In the diagram credit should be given for•        a vertical condenser

Lose M3 and M4 for a distillation apparatus.1

•        an apparatus which would clearly workDo not allow this mark for a flask drawn on its own.Penalise diagrams where the apparatus is sealed.

1

(iii)    Distillation1

Immediately (the reagents are mixed)1

(b)     Keep away from naked flamesAllow heat with water-bath or heating mantle.If a list is given ignore eye protection, otherwise lose this mark.

1

(c)     (i)      Tollens’ or Fehling’s reagentsIncorrect reagent(s) loses both marks.Accept mis-spellings if meaning is clear.

1

Silver mirror / red ppt. formedAccept ‘blue to red’ but not ‘red’ alone.

1

(ii)     Sodium carbonate (solution) / Group II metalAllow indicator solutions with appropriate colours.

Accept any named carbonate or hydrogen carbonate.1

Effervescence / evolves a gasAccept ‘fizzes’.

1

(d)     Propanoic acidIf this mark is lost allow one mark if there is reference to stronger intermolecular forces in the named compound.Lose M1 and M3.

1

Contains hydrogen bonding1

Some comparison with other compounds explaining that the intermolecular forces are stronger in propanoic acid

1[15]

Q3.(a)     Functional group (isomerism)

1

(b)    

M1 Tollens’ (reagent)(Credit ammoniacal silver nitrate OR a description of making Tollens’)(Ignore either AgNO3 or [Ag(NH3)2

+]or “the silver mirror test” on theirown, but mark M2 and M3)

M2 silver mirror

OR

black solid/precipitate(NOT silver precipitate)

M3 (stays) colourlessor no change or no reaction

M1 Fehling’s (solution) orBenedict’s solution(Ignore Cu2+(aq) orCuSO4 on their own, but mark on to M2 and M3)

M2 Red solid/precipitate(Credit orange or brown solid)

 

 

M3 (stays) blueor no change or no reaction

Mark on from an incomplete/incorrect attempt at the correctreagent, penalising M1

No reagent, CE=0Allow the following alternativesM1 (acidified) potassium dichromate(VI) (solution)M2 (turns) greenM3 (stays) orange/no changeORM1 (acidified) potassium manganate(VII) (solution)M2 (turns) colourlessM3 (stays) purple/no changeFor M3Ignore “nothing (happens)”

Ignore “no observation”3

(c)     (Both have) C=O OR a carbonyl (group)1

(d)     (i)      (Free-) radical substitution ONLYPenalise “(free) radical mechanism”

1

(ii)     InitiationCl2 → 2Cl•

Penalise absence of dot once only.

First propagationCl• + CH3CH2CH3 → •CH2CH2CH3 + HClOR C3H8

Penalise incorrect position of dot on propyl radical once only.Penalise C3H7• once only

Second propagationCl2 + •CH2CH2CH3 → CH3CH2CH2Cl + Cl•

OR

C3H7ClAccept CH3CH2CH2• with the radical dot above/below/to the side of the last carbon.

Termination (must make C6H14)2 •CH2CH2CH3 → C6H14 or CH3CH2CH2CH2CH2CH3

Use of the secondary free radical might gain 3 of the four marks

4

(e)     Mr = 44.06352 (for propane)Mr = 43.98982 (for carbon dioxide)

Mark independently

M1 a correct value for both of these Mr values.

M2 a statement or idea that two peaks appear (in the mass spectrum)

OR

two molecular ions are seen (in the mass spectrum).2

[12]

Q4.(a)     (i)      C6H12O6 → 2C2H5OH + 2CO2;

(penalise C2H6O once only in this question)1

(ii)     Concentrated H2SO4 OR concentrated H3PO4 OR Al2O3;(penalise aqueous or dilute as a contradiction)

1

C2H5OH → C2H4 + H2O OR C2H5OH → H2C = CH2 + H2O;(penalise CH2

.CH2 and CH2-CH2 and CH2 : CH2 for ethene)1

(b)     Nickel OR Ni OR platinum OR Pt OR palladium OR Pd;1

Hydrogen OR H2;1

(c)     (i)      C18H34O2 Only;1

C9H17O    Only;(empirical formula is not consequential on molecular formula)

1

(ii)     (An unsaturated compound) contains (at least) one double bond

OR

         Contains C=C;(must be a positive statement)

1

(iii)     M1: Bromine water

         OR

         Br2(aq)

         OR

         Bromine

         OR

         Br2;(penalise “bromide water”, but mark on)

1

M1: decolourised or goes colourless

OR

         from brown/red/orange/yellow to colourless;(Must be “colourless” not “clear” for M2)(chemical error if no reagent or wrong reagent, loses both marks) (credit KMnO 4 for M1, (purple) to colourless for M2 (if acidified) OR (purple) to brown/brown precipitate (if alkaline or unspecified) (No credit for hydrogen or iodine as reagents)

1[10]

Q5.D

[1]

Q6.(a)     For 2 marks at least one correct reference either to M r or value to 5

decimal places requiredQoL (associated with the bold statement here)

M1  Compounds 1 and 3 (butanal and butanone) have the same Mr (to 5dp)        because either

It may be possible to award 2 marks if there is a clear statement about oxygen having a different precise Ar in the context of the comparison

•    they contain the same number of atoms of the same / each element

•    are both C4H8O

•    have the same molecular formulaNB The word “similar” does not mean “the same”

•    contain the same number of C, H and O atoms

M2  Compound 2 (pentane) has a different Mr (to 5dp) because either

•    it has different numbers of atoms of different elements

•    is C5H12 / only contains C and H

•    different molecular formula

•    does not contain oxygen (atom) / C=O2

(b)     WithTollens’ (reagent)

M1 silver mirror

OR black solid/precipitate

(NOT silver (mirror) precipitate)

M2 (stays) colourless

OR no change / no reaction

OR no silver mirror

With Fehling’s (solution)

M1 Red solid/precipitate

(Credit orange or brown solid)

M2 (stays) blue

OR no change / no reaction

OR no red solid

OR no (red) precipitateN.B No mark is awarded for the reagent

If no reagent given allow 1 mark for a consistent statement of M1 and M2For M2, ignore “nothing (happens)”And ignore “no observation”

2[4]

Q7.(a)     Reagent

AcidifiedK2Cr2O7

AcidifiedKMnO4

I2 / NaOH

NamedRCOOH with HCl or H2SO4

NamedRCOCl

Allow names including potassium permanganateWrong or no reagent CE = 0

1

P (ketone)no reactionno reactionYellow pptno reactionno reaction

Penalise incorrect formulae or incomplete reagent, such as K2Cr2O7 or acidified dichromate, but mark on.

1

S (2° alcohol)(orange to) green(purple to) colourlessno reactionfruity or sweet smellMisty fumes

Allow no change or nvc but penalise nothing or no observationIf 2 reagents added sequentially or 2 different reagents used for P and S then CE = 0

1

(b)     Tollens’silver mirror / solid

1

Fehling’s / Benedictsred ppt

1

(c)     G

PIf not P then no marks for clip

15 OR five

1

(d)     C4H12SiMust be molecular formulaWrong substance CE = 0 for clip

1

Any two from•        One or single peak OR all (four) carbon atoms are equivalent or one

environment1

•        upfield from others or far away from others or far to right•        non toxic OR inert•        low boiling point or volatile or easy removed from sample

Ignore and don’t credit single peak linked to 12 equivalent H or has a peak at δ = 0but use list principle for wrong statements

11

(e)     Figure 1 is RIf not R cannot score M2

M11

90−150 (ppm) or value in range is (two peaks for) C = C / alkene

M21

Figure 2 is TIf not T cannot score M4 or M5

M31

50-90 (ppm) or value in range is C—O or alcohol or ether

M41

two peaks (so not S which would have only one)

M51

(f)

 1

Answers include

 Not allow S

 because V must be an isomer of S

[17]

Q8.Identification of acid by suitable method eg named indicator, named carbonate, specified reactive metal

Ignore any reference to the smell of the ester.1

with expected resultsDo not allow the use of any instrumental method eg i.r. or n.m.r.; must be a chemical test.

1

Identification of alcohol by suitable method eg oxidation by acidified potassium dichromate(VI)

1

with expected results1

[4]

Q9.1-chloropropane        no visible change

Accept ‘small amount of precipitate’ or ‘precipitate forms slowly’.

1

  ethanoyl chloride        white precipitateAccept ‘large amount of precipitate’ or ‘precipitate forms immediately’.

1

[2]

Q10.(a)     (i)

 

  The addition         followed by           the addition ofof AgNO3             concentrated              NH3(aq)

Observation with NaBr(aq)

Cream or off whiteprecipitate or solid (1)

Precipitate dissolves (1)

Observation with NaI(aq)

Yellow precipitate or solid (1)

Precipitate insoluble or no change (1)

(ii)     Ag F is soluble;5

(b)     (i)      identity:         [Ag(S2O3)2]3–;1

(ii)     equation:       AgI + 2S2O32– → [Ag(S2O3)2]3– + I–

1

(iii)     use:              in photography or as a fixer;1

(c)     (i)      Structure

 1

Observation:     Vigorous or violent or exothermic reaction                 or fumes or white precipitate formed immediately

1

(ii)     Structure:

 1

Observation:     No immediate precipiate or reaction

         OR

                          white precipitate formed very slowly;1

(d)     (i)      Silver-containing complex:     [Ag(NH3)2]+;1

Shape:               Linear;1

(ii)     Structure

 1

Explanation: Methanoic acid contains an aldehyde group;1

(iii)     H2CO3 or CO2 or OC(OH)NH2 or (NH2)2 CO or (NH4)2 CO3

OR

HCOONH4 ;1

[17]

Q11.Test            bromine (water) / iodine

Accept ‘Br2’ or ‘bromine in a named solvent’.Do not accept ‘Br’Use of UV light, CE (lose next mark as well)

1

Observation   orange / yellow / (red-)brown to colourlessMust have correct reagent to score this mark.For I2, allow red-brown / purple to colourless.

1[2]

Q12.(a)     M1 concentrated sulfuric acid OR c(onc) H2SO 4

If no reagent or incorrect reagent in M1, CE= 0 and no marks for M2 or M3

M2 (cream solid) turns orangeOR orange / red / brown fumes / gas / vapour

If dilute sulfuric acid OR “aq” (alone) CE=0

M3 (yellow solid) turns blackOR purple fumes / gas / vapourOR correct reference to H2S observation (eg bad egg smell)

If H2SO4 / sulfuric acid given but not stated whether dilute or concentrated, penalise M1 and mark on for M2 and M3If incorrect formula for the acid, penalise M1 but mark M2 and M3

OR as an alternative

M1 concentrated ammonia OR c(onc) NH3

If NH3 / ammonia / aq ammonia given, but not stated as concentrated OR if dilute ammonia given, penalise M1 but mark on for M2 and M3Ignore “partially” and ignore “clear” in M2

M2 (cream solid) dissolves / solution formed

M3 precipitate remains / does not dissolve / insolubleOR no reaction / no change / (yellow solid) turns to white solid

If incorrect formula for ammonia, penalise M1 but mark M2 and M3In M3 for ammonia.ignore “nothing (happens)”.ignore “no observation”.

3

(b)     M1 AgNO3 OR silver nitrate OR any soluble silver saltIf no reagent OR incorrect reagent in M1, CE= 0 and no marks for M2 OR M3

M2 white precipitate or white solid / white suspensionAn insoluble silver salt OR Tollens’ OR Ag OR ammoniacal silver nitrate or HCl / AgNO3 CE= 0 for the clip.

M3 remains colourless OR no reaction OR no (observed) change OR no precipitate

For M1Credit acidified (OR HNO3) silver nitrate for M1 and mark on.If silver ions or incorrect formula for silver nitrate, penalise M1 but mark M2 and M3

Credit alternative test for nitrate ionsFor M2Ignore “cloudy solution” OR “suspension”.For M3Ignore “nothing (happens)”.Ignore “no observation”.Ignore “clear”.Ignore “dissolves”.

3

(c)     M1 Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)If no reagent or incorrect reagent in M1, CE= 0 and no marks for M2 or M3

Either OrderM2     (stays) Orange / red / yellow / brown / the same

OR no reaction OR no (observed) changeOR reference to colour going to cyclohexane layer

No credit for combustion observations; CE=0For M2 in every case.Ignore “nothing (happens)”.Ignore “no observation”.Ignore “clear”.

M3 decolourised / goes colourless / loses its colourWith bromine (water)For M1, it must be a whole reagent and / or correct formula.If oxidation state given in name, it must be correct.For M1 penalise incorrect formula, but mark M2 and M3

OR as an alternative

Use KMnO4/H2SO4

M1 acidified potassium manganate(VII) or KMnO4/H2SO4

OR    KMnO4/ H+ OR acidified KMnO4

M2 (stays) purple or no reaction or no (observed) changeWith potassium manganate(VII)For M1

M3 purple to colourless solution OR goes colourlessIf “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 but mark M2 and M3

Credit alternative test using iodine (for M1)M2 (brown) to purple or accept no change, M3 colourlessCredit alternative test using concentrated H2 SO4

M2 no change, M3 brownCredit alkaline / neutral KMnO4 for possible full marks but M3 gives brown precipitate or solution goes green.

3

(d)     M1 Tollens’ (reagent) OR ammoniacal silver nitrate OR a description of making Tollens’(Ignore either AgNO3 or [Ag(NH3)2

+] or “the silver mirror test” on their own, but mark M2 and M3)M2 silver mirrorOR black solid / precipitate (Ignore silver precipitate)M3 (stays) colourless or no reaction or no (observed) change

If no reagent or incorrect reagent in M1, CE= 0 and no marks for M2 or M3For M3 in every caseIgnore “nothing (happens)”.Ignore “no observation”.

Alternative using Fehling’s (solution)M1 Fehling’s (solution) or Benedict’s solution(Ignore Cu2+(aq) or CuSO4 on their own, but mark M2 and M3)M2 Red solid / precipitate (Credit Orange or brown solid)M3 (stays) blue or no reaction or no (observed) change

With potassium dichromate(VI)For M1If “dichromate” or “(potassium) dichromate(IV)” or incorrect formula or no acid, penalise M1 but mark M2 and M3

Alternative using K2Cr2O7/H2 SO4

M1 acidified potassium dichromate or K2Cr2O7/H2SO4

OR K2Cr2O7/H+ OR acidified K2Cr2O7

M2 (Orange to) green solution OR goes greenM3 (stays) Orange or no reaction or no (observed) change

For M3Ignore dichromate described as “yellow” or “red”.

With potassium manganate(VII)For M1If “manganate” or “(potassium manganate(IV)” or incorrect formula or no acid, penalise M1 but mark M2 and M3

Alternative using KMnO4 /H2 SO4

M1 acidified potassium manganate(VII) or KMnO4 /H2 SO 4

OR KMnO 4 /H + OR acidified KMnO 4

M2 purple to colourless solution OR goes colourlessM3 (stays) purple or no reaction or no (observed) change

Credit alkaline / neutral KMnO4 for possible full marks but M2 gives brown precipitate or solution goes green.

3[12]

Q13.(a)     (i)      M1 (Compounds / molecules with) the same structural formula

Penalise M1 if ‘same structure’ or ‘different structural / displayed formula’.

M2 with atoms / bonds / groups arranged differently in space

OR atoms / bonds / groups with different spatial arrangements / different orientation

Ignore references to ‘same molecular formula’ or ‘same empirical formula’.Mark independently.

2

(ii)     

Credit C–H3CCredit C2H5

Penalise C–CH3CH2

1

(b)     M1 Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)If M1, has no reagent or an incorrect reagent, CE=0.Ignore ‘acidified’.

M2    Isomer 1: decolourised / goes colourless / loses its colourFor M1 penalise Br (or incorrect formula of other correct reagent), but mark on.

M3  Isomer 2: remains orange / red / yellow / brown / the same OR no reaction / no (observable) change OR reference to colour going to the cyclopentane layer

For M1, it must be a whole reagent and / or correct formula.If oxidation state given in name, it must be correct. If ‘manganate’ OR ‘manganate(IV)’ or incorrect formula, penalise M1, but mark on.

Alternatives : potassium manganate(VII)

M1 KMnO4 in acid M2 colourless M3 purple

M1 KMnO4 in alkali / neutral M2 brown solid M3 purple

Credit for the use of iodine

M1 iodine (solution / in KI) M2 colourless M3 (brown) to purple (credit no change)

Credit for the use of concentrated H2SO4

M1 concentrated H2SO4 M2 brown M3 no change / colourlessIgnore ‘goes clear’.Ignore ‘nothing (happens)’.Ignore ‘no observation’.No credit for combustion observations.

3

(c)    (i)      (Both infrared spectra show an absorption in range) 1620 to 1680 (cm−1)Ignore reference to other ranges (eg for C–H or C–C).

1

(ii)     The fingerprint (region) / below 1500 cm−1 will be different or its fingerprinting will be different

OR

different absorptions / peaks are seen (in the region) below 1500 cm−1 (or a specified region within the fingerprint range)

Allow the words ‘dip’ OR ‘spike’ OR ‘low transmittance’ as alternatives for absorption.QoL

1

(d)     

All bonds must be drawn.Ignore bond angles.

1

(e)    (i)      M1    Electrophilic additionM1 both words needed.

Penalise one mark from their total if half-headed arrows are used.

M2 must show an arrow from the double bond towards the H atom of the H–Br molecule

M2 Ignore partial negative charge on the double bond.

M3 must show the breaking of the H–Br bondM3 Penalise incorrect partial charges on H–Br bond and penalise formal charges.

M4 is for the structure of the tertiary carbocationPenalise M4 if there is a bond drawn to the positive charge.Penalise once only in any part of the mechanism for a line and two dots to show a bond.

M5 must show an arrow from the lone pair of electrons on the negatively charged bromide ion towards the positively charged carbon atom of either a secondary or a tertiary carbocation

For M5, credit attack on a partially positively charged carbocation structure but penalise M4.Max 3 of any 4 marks in the mechanism for wrong organic reactant or wrong organic product (if shown) or secondary carbocation.Max 2 of any 4 marks in the mechanism for use of bromine.Do not penalise the correct use of 'sticks”.

NB The arrows here are double-headed5

(ii)     M1 Reaction goes via intermediate carbocations / carbonium ionsM1 is a lower demand mark for knowledge that carbocations are involved.

M2 (scores both marks and depends on M1)

Tertiary carbocation / carbonium ion is more stable (than the secondary carbocation / carbonium ion)

OR

Secondary carbocation / carbonium ion is less stable (than the tertiary carbocation / carbonium ion)

M2 is of higher demand and requires the idea that the secondary carbocation is less stable or the tertiary carbocation is more stable. Reference to incorrect chemistry is penalised.A carbocation may be defined in terms of alkyl groups / number of carbon atoms, rather than formally stated.

2

(f)     M1 EliminationM1 credit ‘base elimination’ but no other qualifying prefix.

Penalise one mark from their total if half-headed arrows are used.

M2 must show an arrow from the lone pair on oxygen of a negatively charged hydroxide ion to a correct H atom

Penalise M2 if covalent KOH

M3 must show an arrow from a correct C–H bond adjacent to the C–Br bond to a correct C–C bond. Only award if an arrow is shown attacking the H atom of a correct adjacent C–H bond (in M2)

M4 is independent provided it is from their original molecule BUT penalise M2, M3 and M4 if nucleophilic substitution shown

Award full marks for an E1 mechanism in which M2 is on the correct carbocation

NB The arrows here are double-headedPenalise M4 for formal charge on C or Br of the C–Br bond or incorrect partial charges on C–Br.Penalise M4 if an additional arrow is drawn from the Br of the C–Br bond to, for example, K+.Ignore other partial charges.Penalise once only in any part of the mechanism for a line and two dots to show a bond.Max 2 of any 3 marks in the mechanism for wrong reactant or wrong organic product (if shown) or a correct mechanism that leads to the alkene 2-methylbut-2-ene.Credit the correct use of “sticks” for the molecule except for the C–H being attacked.

M5 hydroxide ion behaves as a base / proton acceptor / electron pair donor / lone pair donor

Penalise M5 if ‘nucleophile’.5

[21]

Q14.(a)     If 2 stage test for one compound, award no marks for that compound, eg no

mark for ROH or RX to alkene then Br2 test. If reagent is wrong or missing, no mark for that test; if wrong but close/incomplete, lose reagent mark but can award for correct observation. In each test, penalise each example of wrong chemistry, eg AgClr2

propan-1-ol

acidifiedpotassiumdichromate

sodium

Named acid + conc H2SO4

named acyl chloride

PCl5

M11

(orange) turns green

effervescence

Sweet smell

Sweet smell /misty fumes

Misty fumes

M21

propanal

add Tollens or Fehlings / Benedicts

acidifiedpotassiumdichromate

Bradys or 2,4-dnphif dichromate used for alcohol cannot be used for aldehyde

M31

Tollens: silver mirror or Fehlings/ Benedicts: red ppt

(orange) turns green

Yellow or orange ppt

M41

propanoic acid

Named carbonate/ hydrogencarbonate

water and UI (paper)

Named alcohol + conc H2SO4

sodium or magnesium

PCl5if sodium used for alcohol cannot be used for acid

M51

effervescence

orange/red

Sweet smell

effervescence

Misty fumesif PCl5 used for alcohol cannot be used for acid

M61

1-chloro propane

NaOH then acidified AgNO3

AgNO3

If acidification missed after NaOH,no mark here but allow mark for observation

M71

white ppt

white ppt

M81

(b)      oxidation (of alcohol by oxygen in air)

M11

absorption at 1680 -1750 (due to C=O)Must refer to the spectrum

M21

comparison of polarity of molecules or correct imf statement:propanone is less polar OR propan-2-ol is more polarOR propanone has dipole-dipole forcesOR propan-2-ol has hydrogen bonding

M31

about attraction to stationary phase or solubility in moving phasePropan-2-ol has greater affinity for stationary phase or vice versaOR propanone is more soluble in solvent/moving phase or vice versa

M41

[12]

Q15.

(a)     (i)       Allow [ClCH2CO]+

1

(ii)      

M1 for arrow from inside hexagon to C or + on C on correct electrophileM2 for structure of intermediate•      Horseshoe centred on C1;•      + in intermediate not too close to C1 (allow on or “below” a line from C2 to C6)M3 for Arrow from bond to H into ring•      Allow M3 arrow independent of M2 structure•      + on H in intermediate loses M2 not M3•     Ignore Cl- removing H+

111

(b)     Reagent

Water

(Aqueous) silver nitrate

NaOH followed by acidified silver nitrate

(Water +) named indicatorNamed alcoholNa2CO3 or NaHCO3

Ammonia1

P

No reaction

No reaction (or slow formation of ppt)

No reaction (or slow formation of ppt)

No colour changeNVCNVCNo reactionDo NOT awardNo observation

1

Q

Steamy /misty/ white fumes

White precipitate (immediately formed)

White precipitate (immediately formed)

Indicator turns to correct acid colourFruity or sweet smell or misty fumesFizzing or effervescence (not just gas produced)White smoke

1

(c)     (i)     

 One unit onlyMust have trailing bondsIgnore n and brackets

allow  1

(i)       Allow CO for C=O

1

(d)     (i)       One unit onlyMust have trailing bondsIgnore n and brackets

1

(ii)     PGA sutures react/dissolve/break down/are biodegradable/ are hydrolysed / attacked by water or nucleophiles /no need to remove

OR Polypropene not biodegradeable/ not hydrolysed / not attacked by water/nucleophiles

1

(Ester links have) polar bondspolypropene contains non-polar bondsignore intermolecular forces

1[12]

Q16.(a)     Bromine (water)

1

Colour change from orange to colourless1

(b)     Add sodium hydrogencarbonate (or alternative named carbonate)Allow suitable correct alternative test e.g.Test the pH with named indicator (e.g. Universal Indicator)

1

Propanoic acid will produce effervescence / bubblesPropanoic acid would turn Universal Indicator red

1

(c)     Tollen’s reagent

1

(Colourless solution to) silver mirror1

OR

Fehling’s solution

(Blue solution to) brick red precipitate

(d)     Absorption at 1680–1750 cm−1 caused by C=O1

No absorption at 1620−1680 cm−1 caused by C=C1

No absorption at 3230–3550 cm−1 due to −OH (alcohol)1

No absorption at 2500–3000 cm−1 due to −OH (acid)1

[10]

Q17.(a)    M1        Ester 1

If Ester 2, can score M3 only.1

M2        peak at δ = 4.1     due to     

When marking M2 and M3, check any annotation of structures in the stem at the top of the page.

1

M3        (δ = 4.1 peak is) quartet as adjacent / next to / attached to CH3

1

M4        Other spectrum quartet at δ = 2.1-2.6 (or value in this range)1

(b)     M1        Quaternary (alkyl) ammonium salt / bromide1

M2        CH3Br or bromomethanePenalise contradictory formula and name.

1

M3        Excess ( CH3Br or bromomethane)Mention of acid eg H2SO4 OR alkali eg NaOH loses both M2 and M3.

1

M4        Nucleophilic substitutionCan only score M3 if reagent correct.Ignore alcohol or ethanol (conditions) or Temp.

1

(c)      

  Bromine

(penalise Br butmark on)

Acidified KMnO4

(Penalise missing acidbut mark on)

Wrong reagent = no marks.If bromine colour stated it must be red, yellow, orange, brown or any combination, penalise wrong starting colour.

1 

Benzene no reaction / colour remains / no (visible) change

no reaction / colour remains / no (visible) change

Ignore ‘clear’, ‘nothing’.Allow colour fades slowly.Allow ‘nvc’ for no visible change.

1 

cyclohexene (Bromine) decolourised

(Acidified KMnO4) decolourised

1[11]

Q18.(a)     2,2,4-trimethylpentane

This answer only but ignore punctuation1

(b)     M1    (fractional or simple) distillationIncorrect process in M1 CE=0If M1 blank, mark on for M2 and M3 (ignore boiling, condensing)

1

M2    idea that isooctane / the one with the lower boiling point boils (first) (or reaches top of column first)

Ignore reference to octane boiling and being collected at higher temperatureIf temperature referred to, should be between 99 and 124°C“it” refers to isooctaneM2 – allow vaporises/evaporates first

1

M3    idea that isooctane condenses / liquefies and collectedPenalise M2 and M3 if octane boils firstIn M2 and M3 – if no specific reference to individual alkanes, could score one mark for M2 + M3 combined if M2 and M3 both otherwise correctM2 and M3 must refer to a laboratory apparatus (not to an industrial process)

1

(c)     C8H18 + 12½O2 → 8CO2 + 9H2OAccept multiples; ignore state symbolsAccept any correct structural representation of isooctane

1

(d)     M1    Alternative route/mechanism/pathway1

M2    With lower activation energyAccept Ea for activation energy

1

(e)     2CO + 2NO → 2CO2 + N2

Accept multiples; ignore state symbols1

(f)      M1    to reduce amount of metals needed / small amount of metal neededRelates to low amount of metal

1

M2    Increase / maximise / produce large surface area or to give catalyst a larger surface area: volume ratio or so that high(er) proportion of atoms/metal is on surface

Is related to large surface area1

(g)     M1    bromine (water or in organic solvent or CCl4) / Br2 (aq) / Br2

No reagent or an incorrect reagent (e.g. bromide), CE=0;Penalise Br (or incorrect formula of other correct reagent) but mark on for M2It must be a whole reagent and/or correct formulaIf oxidation state given in name, it must be correctIf ‘manganate’ or ‘manganate(IV)’ or incorrect formula, penalise M1 but mark onIgnore ‘acidified’

1

M2    (orange/yellow to) colourless / decolourised / loses its colourIgnore goes clearIgnore brown/red, but penalise other incorrect colours

1

Alternatives:M1 = potassium manganate(VII), M2 = colourlessM1 = conc sulfuric acid, M2 = brownM1 = iodine, M2 = colourless

[12]

Q19.C

[1]

Q20.(a)     OH AND alcohol

IGNORE hydroxy(l)

1

(b)      A = butan-2-ol / CH3CH(OH)CH2CH3

If formulae given then must be unambiguousIf both formula and name given then formula must match name for mark to be awarded

1B = butan-1-ol / CH3CH2CH2CH2OH

1Product from A / P is a ketone ANDProduct from B / Q is an aldehyde

Penalise reference to incorrect class of alcohol1

(c)      Type of Bond: C=C1

 Must show all bonds in Isomer C including O–H bond

1Reagent: conc. H2SO4 / conc. H3PO4

If incorrect attempt at correct reagent, mark onApply list principle for reagents and conditions marksConc required - may appear on conditions lineNOT (aq) For M3 even if seen on conditions lineALLOW        Reagent = Al2O3

          Condition = ‘passing vapour over hot solid’ owtte1

Conditions: 180 °C / High temp / Hot / Reflux /ALLOW stated temp in range 100-300 °C/373-573 KIGNORE ‘heat’M4 dependent on correct reagent in M3

1

(d)      (i)      S = aldehyde/CHO AND T = carboxylic/COOH/CO2H1

T forms hydrogen bonds1

(Which are) stronger than / need more energy to break than forces between molecules/IMFs in S ora (or reverse argument)

If implication of breaking covalent bonds max M1 only1

(ii)     (No oxidation has occurred as..)

(Still) contains peak at 3230−3550 cm-1 due to O−H/alcohol

Does not contain peak at 2500−3000 cm-1 due to O−H/carboxylic acid

Does not contain peak at 1680−1750 cm-1 due to C=OMust have wavenumber range (or value within range) and bond or functional group to score each mark.

Any 2[13]