Organic Analysis - Infrared Spectroscopy - Mark schemes

Q1.(a)     M1 Safety (in Process 1)

Sodium hydroxide / alkali is corrosive / harmful / caustic or sodium hydroxide is alkali(ne)

Ignore references to chromium compounds

OR

Bromine compounds are toxic / poisonous“Carbon-neutral” alone is insufficient for M2

M2 EnvironmentalIgnore references to greenhouse gases

Process 2 could be used as a carbon sink / for carbon capture

OR

uses waste / recycled CO2 / CO2 from the factory / CO2 from the bioethanol (orbiofuel) production

OR

reduces or limits the amount of CO2 released / given out (into the atmosphere)

OR

Process 2 uses renewable glucose / renewable resource(s)2

(b)     (i)      M1 nucleophilic substitutionFor M1, both words required

M2 must show an arrow from the lone pair of electrons on the oxygen atom ofthe negatively charged hydroxide ion to the C atom.

Penalise M2 if covalent NaOH / KOH is usedPenalise one mark from M2 or M3 if half-headed arrows are used

M3 must show the movement of a pair of electrons from the C–Br bond to theBr atom. Mark M3 independently provided it is from the original molecule

Penalise M3 for formal charge on C of the C–Br or incorrect partial charges on C–BrPenalise once only for a line and two dots to show a bond.

For M2 and M3 award full marks for an SN1 mechanism

For M2 and M3, maximum 1 of 2 marks for the mechanism if wrong reactant is used.Penalise M3 if an extra arrow is drawn from the Br of the C–Br bond to, for example, K+

Accept the correct use of “sticks

NB The arrows here are double-headed3

(ii)     M1   B

M2   C

M3   A3

(c)     M1 fermentationMark M2 to M4 independently

Three conditions in any order for M2 to M4Penalise “bacteria” and “phosphoric acid” using the list principle

M2    (enzymes from) yeast or zymase

M3    25°C ≤ T ≤ 42°C  OR   298 K ≤ T ≤ 315 KIgnore reference to “aqueous” or “water”, “closed container”, “pressure, “lack of oxygen”,“concentration of ethanol” and “batch process” (i.e. not part of the list principle)

M4    anaerobic / no oxygen / no air OR neutral pH4

(d)     M1    primary OR 1° (alcohol)Mark independently

M2    acidified potassium or sodium dichromateFor M2, it must be a whole reagent and/or correct formulae

OR    H2SO4 / K2Cr2O7 OR H+ / K2Cr2O7

Do not penalise incorrect attempt at formula if name is correct or vice versaAccept phonetic spellingIf oxidation state given in name, it must be correct.For M2 accept acidified potassium manganate(VII)

OR    correct combination of formula and name

M3

HOCH2CH2CH2CH2OH + 4[O] HOOCCH2CH2COOH + 2H2OFor M3 structures must be correct and not molecular formula

3[15]

Q2.

(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 reagent1

(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]

Q3.B

[1]

Q4.(a)     GLC or distillation

1

(b)     C=O1

(c)     (i)      Cl has two isotopes1

(ii)     1

C4H7ClO+• →  + C2H4Cl•1

(d)     (i)      e.g. CDCl3 or CCl41

(ii)     Si(CH3)4

1

(e)     0 and 31

(f)     

 1

(g)     CH3CH2CH2COCl or (CH3)2CHCOCl1

[10]

Q5.D

[1]

Q6.(a)     R: O-H (alcohols) (1)

S: C=O or carbonyl (1)2

(b)     aldehyde (1)   -CHO or RCHO (1)1

(c)     (i)      Reason 1: TMS inert or non-toxic or volatile / easily removedReason 2: single (intense) peak               peak of 12 protons               has 12 equivalent protons               all protons in same environmentOR               peak / signal upfield of others               highly shielded               more shielded               peak away from others or δ = 0 or low

not solvent, not cheapany 2 reasons × (1)

(ii)     Solvent: CDCl3 or CCl4 (NOT D2O)Reason: proton free (1)

allow no hydrogens (atoms)NOT H+ / hydrogen ions

4

(d)     (i)       (1)

(ii)     –OH (1)

(iii)     –CH2–CH2– (1)3

(e)      (1)1

[11]

Q7.(a)     Pentan-2-one

1

(b)     (i)      1680 – 1750 (cm–1)1

(ii)     3230 – 3550 or 1000 – 1300 (cm–1)1

(iii)     41

(c)      

Reagent K2Cr2O7/H+ KMnO4 /H+ Na CH3COOH/H2SO4

1

with C no reaction no reaction no reaction no reaction 1

with D goes green goes colourless

effervescence

smell 1

(penalise incomplete reagent e.g. K2Cr2O7 or Cr2O7 2–/H+ then

mark on)

(d)     Reagent Tollens Fehlings or Benedicts 1

with E silver(mirror)

red ppt or goes red(not red solution)

1

       [9]

Q8.         (a)     A       any C5 alkene

1

B

 1

(b)     C

 

         or CH3COOH    or      HCOOCH3

1

          D

         or HOCH2CHO1

(c)     E

 1

          F

 1

(d)     G

 1

          H

 1

(e)     I

 1

          J

   NOT hex-3-ene1

[10]

Q9.(a)     Identity of X; 2-methylpropene (1)

Absorption at 1650 cm–1 indicates an alkene present (1)OR a chemical answer e.g. Br2 (aq) brown to colourless

2

(b)     ReagentsStep 1 KOH (allow NaOH) (1)    alcoholic (1)         warm (1)

Only allow solvent and warm if reagent correct

Step 2 HBr (1)

Mechanism:                    A → X

 Or a carbocation mechanism

Mechanism                     X → B

 11

(c)     A gives three peaks (1)B gives one peak (1)

Allow one for “A has more peaks than B” when no number of peaks is given

2[15]

Q10.(a)      Fractional distillation (under reduced pressure)

1

(b)     BaSO4 insoluble / remove by filtrationDo not allow answers which refer to reaction rate

1

(c)     Both contain OH groupAllow OH stretch in ir spectrum of each compoundDo not allow ‘same bonds’

1[3]

Q11.

(a)     (i)     

 or RCOCH3;(or description in words)(ignore trailing bonds)

1

(ii)     H3C—O or ROCH3;(allow 1 if both (i) and (ii) give CH3- or H3C– only)

1

(iii)     CH2CH2 or two adjacent methylene groups;1

(iv)

 

OR

CH3COCH2CH2OCH3;1

(b)     (i)      OH in acids or (carboxylic) acid present

(ii)

 

(c)      

reagent K2Cr2O7 /H+ KMnO4 /H+

Y no reaction no reaction

Z orange to green or turns green

purple to colourless

or turns colourless

5[9]

Q12.(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)

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

M2 silver mirror

OR

black solid/precipitate(NOT silver precipitate)

M3 (stays) colourlessor no change or no reaction

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]

Q13.(a)     Allow 1 mark each for any correctly drawn primary, secondary and

tertiary alcohol of molecular formula C4H8O3

          Tertiary alcohol cannot be oxidised1

(b)     Region 1500–400 cm–1

1

exact match to spectrum of known compound1

(c)                       A                                               B       CH3CH2CH2OH                       CH3CH2–O–CH3 (1)or CH3CH(OH)CH3 (1)

                           C                                               D       one alkene e.g.                     one cycloalkane e.g.

 

CH2=CHCH2CH2CH3

CH3–CH=CH–CH2CH3

(CH3)2C=CHCH3

H2C=C(CH3)CH2CH3

(1) etc

                           E                                                F      CH3CH2CHO (1)                         CH3COCH3 (1)

6[12]

Q14.(a)     M1

Displayed formula for butan-2-ol

 M1 displayed formula must have all bonds drawn out, including the O―H but ignore anglesPenalise “sticks”

M2 Alcohol X is

 M2 structure must be clearly identifiable as2-methylpropan-2-ol and may be drawn in a variety of ways.

M3 Alcohol Y is named (2)-methylpropan-1-ol ONLYM3 must be correct name, but ignore structures

3

(b)     M1 The infrared spectrum shows an absorption/peak in the range3230 to 3550 (cm–1)(which supports the idea that an alcohol is present)

In M1, allow the words “dip”, “spike”, “low transmittance” and “trough” as alternatives for absorption.

M2 Reference to the ‘fingerprint region’ or below 1500 (cm–1)

M3 Match with or same as known sample/database spectraCheck the spectrum to see if alcohol OH is labelled and credit.

OR

M2 Run infrared spectra (of the alcohols)

M3 Find which one matches or is the same as this spectrum.3

(c)     M1 balanced equationC6H12O6 → CH3CH2CH2CH2OH + 2CO2 + H2O                        or C4H9OH

Or multiples for M1 and M3In M1 and M3 penalise use of C4H10O or butan-2-ol once only

M2 Any one from

•        excess/adequate/sufficient/correct amount of/enough/plenty/a good supply of oxygen or air

•        good mixing of the fuel and air/oxygenFor M2, do not accept simply “oxygen” or “air” aloneIgnore reference to “temperature”

M3 CH3CH2CH2CH2OH + 6O2 → 4CO2 + 5H2O

or C4H9OH

M4 A biofuel is a fuel produced from (renewable) biological (re)source(s)

OR

(renewable) (re)source(s) from (a specified) plant(s)/fruit(s)/tree(s)In M4Ignore references to “carbon neutral”Ignore “sugar” and “glucose”

4

(d)     M1 butan-1-ol is a primary or 1° (alcohol)

M2 Displayed formula (ONLY) for butanal CH3CH2CH2CHO

M3 Displayed formula (ONLY) for butanoic acid CH3CH2CH2COOHM2 and M3 displayed formula must have all bonds drawn out including the O―H but ignore angles.If butanal and butanoic acid formulae are both correctly given but not displayed, credit one mark out of two.

M4 Oxidation (oxidised) OR Redox

M5 orange to greenBoth colours required for M5Ignore states

5[15]

Q15.(a)     X (O–H) (alcohols)

penalise acid or missing “alcohol”1

Y C=Oallow carbonyl

1

 NOT acid

4

(b)    

 Allow conseq dibromocompounds following incorrect unbranched alkenes NOT allow dibromocompound consequent on a duplicate alkeneNOT allow monobromocompounds if HBr added

3

 3

6:3:1 either next to correct structure or to none1

Allow a mark for identifying correct dibromocompound with three peakseven if integration ratio is wrong

1

if 6:3:1 missing or wrong, no marks for splitting

Only award a mark for splitting if it is clear which integration number itrefers to

6 singlet or drawn1

3 doublet or drawn1

1 quartet/quadruplet or drawn1

(max 10 marks)[16]

Q16.(a)      OH acid (present in acid not in ester)

Allow absorption at 2500–3000 cm–1 in acid.1

(b)     C=O or (absorption at) 1680–1750 cm–1

(present in acid not in alcohol)Allow correct distinction between 3230–3550 cm–1 for OH alcohol and 2500–3000 cm–1 for OH acid.

1

(c)     Comparison with known spectrum1

(Exact) match (with known spectrum)1

[4]

Q17.(a)     Secondary OR 2° (alcohol);

1

(b)     Spectrum is for butanone (or formula) or butan-2-oneThe explanation marks depend on correctly identifying butanone.

          If butanone is correctly identified, award any two from

•        (Strong) absorption / peak at approximately 1700 (cm–1) /1710 (cm–1) / in the range 1680 – 1750 (cm–1) This

needs to be stated.

•        (Characteristic) absorption / peak for C=O (may be shownon the spectrum in the correct place).

•        No absorption / peak in range 3230 to 3550 cm–1.1

•        No absorption / peak for an OH group.Look at the spectrum to see if anything is written on it that might gain credit.Allow the words “dip” OR “spike” OR “low transmittance” as alternatives for absorption.

2

(c)     Displayed structure for 2-methylpropan-2-ol

 Must have all bonds drawn out but ignore the bond angles

1[5]

Q18.(a)     (i)      Electron pair donor

OR

Species which uses a pair of electrons to form aco-ordinate/covalent bond.

Credit “lone pair” as alternative wordingCredit “electron pair donator”

1

(ii)     Replacement of the halogen (atom) (by the nucleophile)

OR

The carbon-halogen bond/C-X breaks and a bond formswith the nucleophile or between the carbon and the nucleophile

They must describe the idea of substitution in a haloalkane.Accept the idea that a nucleophile replaces the halogen which becomes a halide ionPenalise reference to “halogen molecule” and penalise the idea that the haloalkane contains a halide

1

(iii)     Splitting molecules using/by water

OR

breaking/splitting/dissociating (C¡VX) bond(s)/using/by waterNOT simply the reaction with water or simply the addition of

water.Ignore “compound”

1

(iv)    (Heat) energy/enthalpy required/needed/absorbed (at constantpressure) to break/split it/the (carbon-halogen) bond

OR

(Heat) energy/enthalpy required/needed/absorbed (at constantpressure) for homolysis of the (C–X/the carbon-halogen) bond

Ignore bond formationIgnore “average”

1

(b)

 

M1    must show an arrow from the lone pair of electrons on theoxygen atom of the negatively charged hydroxide ion to thecentral C atom.

M2    must show the movement of a pair of electrons from theC-Br bond to the Br atom. Mark M2 independently.

Award full marks for an SN1 mechanism in which M1 is the attack of thehydroxide ion on the intermediate carbocation.

Penalise M1 if covalent KOH is usedPenalise M2 for formal charge on C or incorrect partial chargesPenalise once only for a line and two dots to show a bond.Max 1 mark for the wrong reactantAccept the correct use of “sticks”

2

(c)     (i)

 

M1    must show an arrow from the lone pair on oxygen of anegatively charged hydroxide ion to the correct H atom

M2    must show an arrow from the correct C-H bond to the C-Cbond and should only be awarded if an attempt has beenmade at M1

M3    is independent provided it is from the original molecule

Award full marks for an E1 mechanism in which M2 is on thecorrect carbocation.

Penalise M1 if covalent KOHPenalise M3 for formal charge on C or incorrect partial chargesPenalise once only for a line and two dots to show a bond.Max 2 marks for wrong reactantAccept the correct use of “sticks” for the molecule except for the C-H being attacked

3

(ii)     M1    Stated that the spectrum has an absorption/absorbance/peak in the range 1620 cm –1 to 1680 (cm–1) or specifiedcorrectly in this range from the spectrum

M2    depends on correct range or wavenumber being specified

M2    (Infrared absorption) due to C=C OR carbon-carbon double bondQoL for correct M1 statement which includes both the word absorption (or alternative) and the correct range or wavenumberAllow “peak” OR “dip” OR “spike” OR “trough”OR “low transmittance” as alternatives for absorption.For M2 it is not sufficient simply to state that an alkene has C=CM2 could be on the spectrumIgnore reference to other absorptions

2[11]

Q19.(a)     (i)      3-bromo-3-methylpentane ONLY

Must be correct spelling but ignore hyphens and commas1

(ii)     Electrophilic addition (reaction)Both words neededAccept phonetic spelling

1

(iii)     M1    Displayed formula of 2-bromo-3-methylpentane

 All the bonds must be drawn out but ignore bond angles

M2    Position(al) (isomerism)Do not forget to award this mark

2

(iv)    Structure of (E)-3-methylpent-2-ene

 The arrangement of groups around the double bond must be clear with the ethyl group attached in the correct order. Ignore bond angles.Accept C2H5 for ethylBe lenient on C ─ C bonds. The main issue here is whether they have drawn an (E) isomer.Accept “sticks” for C ─ H bonds and correct skeletal formula

1

(b)     (i)      M1    R is represented by Spectrum 2

M2    Spectrum 2 shows an infrared absorption/spike/dip/trough/peak with any value(s)/range within the range 1620 to1680 (cm–1) OR this range quoted/identified and thisis due to C=C OR this information could be a correctly labelled absorptionon the spectrum

OR Spectrum 1 does not have an infrared absorption in range1620 to 1680 (cm–1) and does not contain C=C.Award M1 if it is obvious that they are referring to the second spectrum (or the bottom one)M2 depends on a correct M1Ignore other correctly labelled peaksIgnore reference to “double bond” or “alkene”

2

(ii)     Functional group (isomerism)1

(iii)     Cyclohexane

OR

Methylcyclopentane etc.Named correctlyIgnore structures and ignore numbers on the methyl group of methylcyclopentane

1[9]

Q20.(a)     Pentan-2-one

ONLY but ignore absence of hyphens1

(b)     Functional group (isomerism)Both words needed

1

(c)     (i)     

 Award credit provided it is obvious that the candidate is drawing the Z / cis isomerThe group needs to be CHOHCH3 but do not penalise poor C–C bonds or absence of brackets around OHTrigonal planar structure not essential

1

(ii)     Restricted rotation (about the C=C)

OR

No (free) rotation (about the C=C)1

(d)    

M1 Tollens’ (reagent)

(Credit ammoniacal silver nitrate OR a description of making

Tollens’)

(Do not credit Ag+, AgNO3 or [Ag(NH3)2

+] or “the silver mirror test” on their own, but

mark M2 and M3)

M1 Fehling’s (solution) / Benedict’s

(Penalise Cu2+(aq) or CuSO4 but mark M2 and M3)

M2 silver mirror

OR black solid or black precipitate

M2 Red solid/precipitate

(Credit orange or brown solid)

M3 (stays) colourless

OR

no (observed) change / no reaction

M3 (stays) blue

OR

no (observed) change / no reaction

 If M1 is blank CE = 0, for the clipCheck the partial reagents listed and if M1 has a totally incorrect reagent, CE = 0 for the clipAllow the following alternativesM1 (acidified) potassium dichromate(VI) (solution); mark on from incomplete formulae or incorrect oxidation stateM2 (turns) greenM3 (stays) orange / no (observed) change / no reactionORM1 (acidified) potassium manganate(VII) (solution);mark on from incomplete formulae or incorrect oxidation stateM2 (turns) colourlessM3 (stays) purple / no (observed) change / no reaction

In all cases for M3Ignore “nothing (happens)”Ignore “no observation”

3

(e)     (i)      Spectrum is for Isomer 1

or named or correctly identifiedThe explanation marks in (e)(ii) depend on correctly identifying Isomer 1.The identification should be unambiguous but candidates should not be penalised for an imperfect or incomplete name. They may say “the alcohol” or the “alkene” or the “E isomer”

1

(ii)     If Isomer 1 is correctly identified, award any two from

•        (Strong / broad) absorption / peak in the range3230 to 3550 cm–1 or specified value in this rangeor marked correctly on spectrumand(characteristic absorption / peak for) OH group /alcohol group

•        No absorption / peak in range 1680 to 1750 cm–1 orabsence marked correctly on spectrumand(No absorption / peak for a) C=O group / carbonyl group / carbon-oxygen double bond

•        Absorption / peak in the range 1620 to 1680 cm–1

or specified value in this range or marked correctlyon spectrumand

          (characteristic absorption / peak for) C=C group/ alkene / carbon-carbon double bondIf 6(e)(i) is incorrect or blank, CE=0Allow the words “dip” OR “spike” OR “trough” OR “low transmittance” as alternatives for absorption.Ignore reference to other absorptions e.g. C-H, C-O

2[10]

Q21.(i)      More absorption/less transmittance of infrared radiation

by it/water vapour

OR broader absorption by OH

OR less absorption/more transmittance of infrared radiation       by carbon dioxide

Must be comparativeThis may be described and must not be contradictoryCredit answers which refer correctly to “transmittance”(more absorption = less transmittance)

1

(ii)      M1    CO2 contains C=O (stated like this or in words or stronglyimplied) OR is O=C=O

M2    depends on correct M1

OR expected absorption/peak (for C=O) is missing

OR expected absorption/peak (for C=O) is shifted to 2300 (cm–1)

OR asymmetric stretching is occurring (due to C=O)If M1 and M2 not scored, give one mark for eitherNo absorption/peak at 1700 (cm–1)/1715 (cm–1)OR no absorption in the range 1680 – 1750 (cm–1)Ignore “carbon-oxygen bonds”, “C-O bonds”Ignore reference to other absorptionsFor M2Allow “dip” OR “spike” OR “low transmittance” as alternatives for absorption.

2[3]

Q22.(a)     (i)      C

1

(ii)     A1

(iii)    D1

(iv)     B1

(b)     M1 Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)If M1, has no reagent or an incorrect reagent, CE=0Ignore “acidified”For M1 penalise Br (or incorrect formula of other correct reagent), but mark onFor M1, it must be a whole reagent and/or correct formulae

Either orderIf oxidation state given in name, it must be correct.

M2   cyclohexane OR A or the alkane : remains orange / red / yellow / brown /the same OR no reaction OR reference to colour going to cyclohexane layer

For M2 credit “no change”Ignore “nothing”Ignore “nothing happens”Ignore “no observation”

M3   cyclohexene OR D or the alkene : decolourised / goes colourless / losesits colour

For M3, ignore “goes clear”

Alternatives : potassium manganate(VII)

M1 KMnO4 in acid M2 purple M3 colourless

M1 KMnO4 in alkali / neutral M2 purple M3 brown solid

Give appropriate credit for the use of iodine and observationsNo credit for combustion observations

3

(c)     M1   acidified potassium or sodium dichromateFor M1, it must be a whole reagent and/or correct formulae

OR   eg H2SO4 / K2Cr2O7 OR H + / K 2Cr2O7

OR   correct combination of formula and nameIf oxidation state given in name, it must be correct.

M2 oxidation OR oxidised OR redoxDo not penalise incorrect attempt at formula if name is correct or vice versa

M3   secondary / 2o (alcohol)Credit acidified potassium chromate(VI) / H2SO4 + K2CrO4

3

(d)     M1   (free-) radical substitution (mechanism)M1 both words required

M2   Br2     2Br•Penalise absence of dot once only.

M3   Br• + CH4      •CH3 + HBrPenalise + or – charges every time

M4   Br2 + •CH3      CH3Br + Br•Accept dot anywhere on methyl radicalAccept a correct termination step for 1 mark if neither M3 nor M4 are scored; otherwise ignore termination stepsMark independentlyNB If Cl2 is used, penalise every time ( this may be for M2, M3 and M4)If cyclohexane is used, penalise every time (this may be for M3 and M4)

M5   Condition

        ultra-violet / uv / sun light

OR   high temperature

OR   125 °C ≤ T ≤ 600 °C

OR   400 K ≤ T ≤ 870 KFor M5 ignore “heat”

5[15]

Q23.(a)     (i)      M1 Elimination

M1 Credit “base elimination” but no other prefix.

 Penalise M2 if covalent KOHPenalise M4 for formal charge on C or Br of C−Br or incorrect partial charges on C−Br

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

Ignore other partial charges

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

Penalise once only in any part of the mechanism for a line and two dots to show a bond

M4 is independent provided it is from their original molecule, BUT CE=0 for the mechanism (penalise M2, M3 and M4 only) if nucleophilic substitution mechanism is shown

Maximum any 2 of 3 marks for the mechanism for wrong organic reactant or wrong organic product (if shown).Credit the correct use of “sticks” for the molecule except for the C−H being attacked

Award full marks for an E1 mechanism in which M4 is on the correct carbocation

Penalise M4, if an additional arrow is drawn from Br eg to K+

NB These are double-headed arrows4

(ii)     Displayed formula for 3-methylbut-1-ene

 All bonds and atoms must be drawn out, but ignore bond angles

1

(iii)    Position(al) (isomerism or isomer)Penalise any other words that are written in addition to

these.1

(b)    (i)      Displayed formula for 3-methylbutan-2-ol

 All bonds and atoms must be drawn out, but ignore bond angles.

1

(ii)     Any one from

•        Lower / decreased temperature OR cold

•        Less concentrated (comparative) OR dilute KOH

•        Water (as a solvent) / (aqueous conditions)Ignore “pressure”.

1

(iii)    Nucleophilic substitutionBoth words needed - credit phonetic spelling.

1

(iv)    (Strong / broad) absorption / peak in the range 3230 to 3550 cm−1 or specified value in this range or marked correctly on spectrum

Allow the words “dip” OR “spike” OR “trough” OR “low transmittance” as alternatives for absorption.

1[10]

Q24.(a)    OH alcohols

1

(b)     (i)     2.6

 

Ignore any group on RHSMust clearly indicate relevant two H on a C next to C=O

On LHS, penalise H or CH or CH2 or CH3

Ignore missing trailing bonds or attached R groups1

(ii)     2.2

 

Ignore all groups on RHSMust clearly indicate relevant three H on C next to C=OIgnore missing trailing bonds or attached R group

1

(iii)    1.2

 

Or in words: two equivalent CH3 groupsMust clearly indicate two equivalent methyl groups.

Penalise attached HIgnore missing trailing bonds or attached R groups

1

(iv)

 1

[5]

Q25.(a)     (i)      C4H10

Mr          = 4(12.00000) + 10(1.00794)

              = 58.07940 or 58.0794 or 58.079 or 58.08

and           58.1Working is essential, leading to the final value of 58.1 which must be stated in addition to one of the four numbers underlined

1

(ii)     By definitionORThe standard / reference (value / isotope)

Reference to 12C alone is not enough1

(b)     

 All bonds and atoms must be drawnGive credit for the displayed formula for the anion

1

(c)     (i)      H2C = CHCH2OHAny correct representation including correct use of “sticks”.Require the double bond to be shown

1

(ii)     Addition (polymerisation)ONLY this answer

1

(iii)    M1     C = C (in range) 1620 to 1680 (cm−1)

M2     O ‒ H (in range) 3230 to 3550 (cm−1)Award one mark for two correct ranges but a failure to draw out the C = C or O‒H bonds

2

(d)     (i)      CH3COCH3

Any correct representation including correct use of “sticks”1

(ii)     C1

[9]

Q26.Compare spectrum of aldehyde with known spectrum of pentanal

Must be a specific reference to a comparison.1

Exact matchAllow ‘fingerprint regions match exactly’.

1[2]

Q27.(a)      (i)     M1    Initiation

         Cl2 2Cl•Penalise absence of dot once only.Penalise + or – charges every time

M2    First propagationCl• + CH2Cl2 •CHCl2 + HClAccept dot anywhere on CHCl2 radical but if the structure is drawn out, the dot must be on the carbon atom. Penalise this error once onlyPenalise once only for a line and two dots to show a bond.

M3    Second propagationCl2 + •CHCl2 CHCl3 + Cl•Penalise once only for double headed curly arrowsMark independently

3

(ii)     M1    Condition

ultra-violet / uv / sun light

OR    high temperature

OR    400°C ≤ T ≤ 900°C

          M2    Type of mechanism  (free-) radical substitution (mechanism)

2

(b)     (i)      CHCl3 + Cl2 CCl4 + HClAllow X as alternative to CCl4 only if X is clearly identified as CCl4

1

(ii)     M1    Trichloromethane / CHCl3 has a C–H bond

         OR

          X / CCl4 / it has no C–H bond M1 must refer to presence or absence of the C–H bond in a compound

          M2   The infrared spectrum shows(absorption / peak for C–H in range) 2850 to 3300 ( cm–1) is missingM2 answer must refer to / imply the spectrumAllow the words “dip” OR “spike” OR “low transmittance” as alternatives for absorption.Ignore references to other absorptions.

2

(c)     M1 a statement about bond breakage / formation of Cl•C–Cl / carbon-chlorine bond breakage occursOR Cl• / chlorine (free) radical formsOR correct equation CHClF2 Cl• + •CHF2

Penalise M1, if Cl• is formed from Cl2 as the only reaction or an additional reactionDo not penalise an incorrect equation using CHClF2 if correct reference is made to Cl• formation or C–Cl / carbon-chlorine bond breakage

M2    Cl•     +     O3         ClO•     +     O2

M3    ClO•  +    O3              Cl•       +   2O2

M2 and M3 either orderPenalise absence of dot once only.Accept dot anywhere on ClO radical

M4    CHClF2 / chlorine-containing compounds/ CFCs damage / react with /          decrease the ozone layer

ORthis overall decomposition occurs; 2O3 3O2

ORwithout an ozone layer or with a decreased ozone layer, uv radiation is not being “filtered” / prevented from passing through the atmosphere or there is a concern about an increase in skin cancer etc.ORCl• catalyses the decomposition of ozone / a single Cl• causes (chain) reaction

/ decomposition of many ozone molecules / ozone layerAward M4 for the general idea behind the EU justification for banning the use of CFCs as refrigerantsPenalise M4 if overall ozone decomposition equation is incorrectIgnore “greenhouse effect”, “global warming” etc.

4

(d)     (i) 

All bonds must be drawn out1

(ii)     2,3,3,3-tetrafluoropropene / it does not contain chlorine (atoms) / C–Cl (bonds)Ignore “chlorine molecules”

ORIt does not produce Cl• / does not produce chlorine (free) radical(s)ORchlorodifluoromethane does contain chlorine / doesproduce Cl• / does produce chlorine (free) radical(s)ORC–F is too strong and does not break / create radicalsORC–F is stronger than C–Cl

1[14]

Q28.(a)    (i)      CH2O

Atoms in any orderAccept a clear indication that C6H12O6 yields CH2O as the answer

1

(ii)     No peak / no absorption / no C=O in the range 1680 to 1750 (cm−1) (suggesting no evidence of C=O)

Allow the words “dip”, “spike”, “low transmittance” and “trough” as alternatives for absorptionIgnore references to other wavenumbers

1

(b)     M1 C6H12O6  2CH3CH2OH + 2CO2

Penalise (C2H6O)Allow multiples of the equation in M1

Either orderM2 (enzymes from) yeast or zymase

M3 25 °C ≤ T ≤ 42 °C OR 298 K ≤ T ≤ 315 KFor M2 and M3 Ignore “aqueous”Ignore “anaerobic / absence of oxygen”Ignore “controlled pH” Ignore “warm”

3

(c)    (i)      Displayed formula for CH3COOH

   All bonds must be drawn out, but ignore bond angles

1

(ii)     O2 + 4H+ + 4e− 2H2OIgnore state symbolsNegative charge on electron not essentialAccept multiplesAccept electrons subtracted from RHS

1

(iii)    CH3CH2OH + H2O   CH3COOH + 4H+ + 4e–

(C2H6O or C2H5OH)Ignore state symbolsNegative charge on electron not essentialAccept multiplesAccept electrons subtracted from LHS

1

(iv)     M1 Acidified potassium or sodium dichromateFor M1, it must be a whole reagent and / or correct formulae

OR H2SO4 / K2Cr2O7 OR H+ / K2Cr2O7 etc.Do not penalise incorrect attempt at formula if name is correct or vice versa

OR correct combination of formula and nameIf oxidation state given in name, it must be correct, but mark on from an incorrect attempt at a correct reagent.

M2 (requires an attempt at M1)orange to green

Credit acidified potassium chromate(VI) / H2SO4 + K2CrO4

Possible alternativeM1 (acidified) potassium manganate(VII) OR KMnO4 / H2SO4

M2 purple to colourlessOther alternatives will be accepted but M2 is dependent on M1 in every case M2 requires an attempt at a correct reagent for M1Ignore reference to states

2

(d)    (i)      An activity which has no net / overall (annual) carbon emissions to the atmosphere / air

The idea that the carbon / CO2 given out equals the carbon / CO2 that was taken in from the atmosphere / air

OR

An activity which has no net / overall (annual) greenhouse gas emissions to the atmosphere / air.

Answer must refer to the atmosphere or air

OR

There is no change in the total amount of carbon dioxide / carbon /greenhouse gas present in the atmosphere / air

1

(ii)     Renewable / sustainable ONLYIgnore references to global warming or greenhouse gases

1

(iii)    Any one statement about this process from

Subject to weather / climateIgnore “batch”

OR

Depletes food supply OR the land use for (specified) food

OR

Requires use of / uses more fossil fuels

OR

Not carbon-neutral OR CO2 produced during a named process (eg harvest, transport etc.)

OR

Slow process / slow rate of reaction / takes a long time (to grow crops)

OR

This route leads to the production of a mixture of water and ethanol / impure ethanol that requires separation / further processing

1[13]

Q29.(a)     (i)      M1 double-headed curly arrow from the lone pair of the bromide ion to the C

atom of the CH2

Penalise additional arrows.

M2    double-headed arrow from the bond to the O atom

As follows

2

(ii)     M1    nucleophilic substitutionM1 both words needed (allow phonetic spelling).

M2    1-bromo(-2-)methylpropaneM2 Require correct spelling in the name but ignore any hyphens or commas.

2

(b)     M1    hydrolysisFor M1 give credit for ‘hydration’ on this occasion only.

M2    C≡N with absorption range 2220–2260 (cm−1)Credit 1 mark from M2 and M3 for identifying C≡N and either O–H(acids) or C=O or C–O without reference to wavenumbers or with incorrect wavenumbers.

M3    O–H(acids) with absorption range 2500–3000 (cm−1)

OR

C=O with absorption range 1680–1750 (cm−1)

OR

C–O with absorption range 1000–1300 (cm−1)Apply the list principle to M3

3

(c)     (i)      M1 Yield / product OR ester increases / goes up / gets more

M2 (By Le Chatelierߣs principle) the position of equilibrium is driven / shifts / moves to the right / L to R / in the forward direction / to the product(s)

M3 – requires a correct statement in M2

(The position of equilibrium moves)

to oppose the increased concentration of ethanol

to oppose the increased moles of ethanol

to lower the concentration of ethanol

to oppose the change and decrease the ethanolIf no reference to M1, marks M2 and M3 can still score BUT if M1 is incorrect CE=0If there is reference to ‘pressure’ award M1 ONLY.

3

(ii)     M1

Catalysts provide an alternative route / pathway / mechanism

OR

surface adsorption / surface reaction occurs

For M1, not simply ‘provides a surface’ as the only statement.M1 may be scored by reference to a specific example.

M2

that has a lower / reduced activation energy

OR

lowers / reduces the activation energyPenalise M2 for reference to an increase in the energy of the molecules.For M2, the student may use a definition of activation energy without referring to the term.Reference to an increase in successful collisions in unit time alone is not sufficient for M2 since it does not explain why this has occurred.

2[12]

Q30.(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 line

ALLOW        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]

Q31.(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 donorPenalise M5 if ‘nucleophile’.

5[21]

Q32.(a)     Percentage of oxygen by mass = 100 – 40.9 – 4.5 = 54.6

1

  C H O

%Divide by Ar

  = 3.41 = 4.5 = 3.411

Divide by smallest =                                      

Nearest whole number ratio = 1 × 3              1.32 × 3               1 × 3

                                              = 3 : 3.96 : 3

Nearest integer ratio =     3            :            4            :            31

Empirical formula C3H4O3

Empirical formula mass = 88 = molecular formula mass

Therefore, molecular formula is same as the empirical formula - C3H4O3

1

(b)     C6H12O6 2C2H5OH + 2CO2

1

(c)     Advantage – ethanol is produced at a faster rate1

Disadvantage – more energy is used / required in the reaction1

(d)     Air gets in / oxidation occurs1

(e)     Alcohol OH absorption in different place (3230–3550 cm–1) from acid OH absorption (2500–3000 cm–1)

1

The C=O in acids has an absorption at 1680–1750 cm–1

1[10]

Q33.(a)     Method 1

M1 %O = 27.1

 

M2     3         7         1

M3     C3H7O = 59 which is half of Mr so MF = 2EF

OR

Method 2

M1     61% of 118 = 72.0 and 11.9% of 118 = 14.0

M2     72 + 14 = 86 so oxygen = 32 out of 118

OR 27.1% of 118 = 32.0

M3      Method 3Alternative using given molecular formula

 3

(b)     For this question, marks can be awarded either for a description of how the structure is derived or from the given structure itself. The maximum mark to be awarded is nine from the ten marks listed.

Marks fall into three sections:

•        Infrared evidence : two marks are available for use of the infrared evidence, (M1 and M10)

•        Chemical evidence: one mark is available for use of the chemical evidence (M2)

•        N.m.r. evidence: six marks are available for use of the n.m.r. evidence (M3 – M8 inclusive)

plus one mark (M9) for a completely correct structure.

Suggested procedure for marking

First look at the infrared spectrum: marks M1 and M10 may be scored there or in the written answer.

Then look for use of the acidified potassium dichromate(VI) evidence, (M2).

Then look at the final structure: this may lead to the award of marks M3 to M9 as shown on the structures below.

Beware contradictions, e.g. using the chemical evidence they may state that R is a primary or secondary alcohol but then draw a tertiary alcohol. This will lose M2 but may score M3.

The written ‘evidence’ frequently simply contains extracts from the Table B on the Data Sheet and, if only this is given, is unlikely to score many marks.

DescribedOr drawn

M1     Infared peak/absorbance at 3400 (cm-1) = O-H alcohol(reference to ir spectrum needed)

Note: please check the spectrumIf peak at 3000 (cm-1) is identified as acid then cannot score M1 (contradiction)

M10     Either no peak between 1680-1750 (cm-1) so no C=O or not aldehyde/acidOR peak at 1000-1300 (cm-1) so C–O present

Apply list principle to IR analysis for M10

M2     (Acidified potassium dichromate(VI) turns green) so primary alcohol or secondary alcohol or not tertiary alcohol

Ignore aldehyde hereLose M2 if just tertiary alcohol in structure

M3     δ = 3.1 singlet or integration = 1 is O-HAward M3 if structure has 1 O-H group only (can be primary, secondary or tertiary)Lose M3 if more than one OH group shown

M4     two triplets at 1.4 & 3.8 = –CH2–CH2– Allow –CH2–CH2–CH2–

M5     δ = 3.8 means CH2 attached to O (in ether NOT ester)Allow O–CH2–CH2–CH2–C

δ = 1.4 means CH2 attached to C (but not to C=O)

M6     δ = 1.1 (singlet) integration 6 = 2 × equivalent CH3 on same C–C(CH3)2–

M7     δ = 1.1 singlet so no H attached to –C(CH3)2-R–C(CH3)2–R

M8     δ = 3.2 singlet integration 3 = -OCH3

–OCH3

M9     For completely correctIf no structure given then Max 8

R is

 

This close alternative

 would not score M9, but could score up to 8 marks

[12]

Q34.(a)     M1    have the same molecular formula

or are C3H6Oor both have the same number/amount of each type of atom or same amount of each elementor are isomers

Not just the same atoms;1

M2    identical / exactly the same / same precise (relative) molecular mass / formula mass / Mr

Same (relative) molecular mass / formula mass / Mr is NOT enough got score M2Allow same accurate (relative) molecular mass / formula mass / Mr

Ignore reference to number of decimal places1

(b)     M1    prop-2-en-1-olMust refer to this compound clearly by name or structure (not to alcohol alone); ignore minor slips in name/structure

1

M2    O(-)H (alcohol) and 3230–3550 (cm−1), orC=C and 1620–1680 (cm−1)

Marked independently from M1Could score from bond labelled on correct signal on spectrumAllow any value within these rangesIf additional incorrect signals given penalise M2Ignore signals below 1500 cm−1 and C-H signals

1

(c)     (i)      Determine the level by looking at the chemical content. (NB - If there is clear breakage of covalent bonds then max level 2 (max 3 marks).

(ii)     The mark within that level is then determined by looking at how coherent and logical the answer is and by use of terminology; start at the higher mark and penalise poor terminology/explanation; examples of terminology that would reduce the mark to the lower one:

•        reference to van der Waals ‘bonds’ or dipole-dipole ‘bonds in relevant compounds that are being credited

•        uncertainty about whether hydrogen bonds are the O-H bonds within or are forces/bonds between molecules (if the alcohol is being credited)

•        use of ‘vdw’ or ‘dip-dip’ unless these terms ‘van der Waals’ for ‘dipole-dipole’ have been used elsewhere in answer (note that IMF and H-bond would not be penalised)

(iii)     If the answer does not achieve level 1, then 1 mark maximum could be scored for any correct point from the list of indicative content

Level 3•        Relative order of boiling points of all three compounds•        Strongest intermolecular force of all three compounds identified•        Answer explains this coherently and logically and uses correct terminology for

all three compounds5-6 marks

Level 2•        Relative boiling points of two compounds correctly compared•        Strongest intermolecular force for these two compounds correctly identified•        Answer explains this coherently and logically and uses correct terminology for

these two compounds3-4 marks

Level 1•        One compound with the highest or lowest boiling point is correctly identified•        Strongest intermolecular force for that one compound identified•        Answer explains this coherently and logically and uses correct terminology for

this one compound•        Allow 1 mark for individual correct point from indicative content on the right if

no other mark scored1-2 marks

Level 0None of the indicative chemistry content given.

0 marks

Indicative chemistry content:• Correct order (highest to lowest) = prop-2-en-1-ol > propanal > butane• Prop-2-en-1-ol has hydrogen bonds• Propanal has (permanent) dipole-dipole forces• Butane has van der Waals’ forces• Strength of intermolecular forces: hydrogen bonds > dipole-dipole > van der Waals(Note - actual values for reference are prop-2-en-1-ol 97°C, propanal 46°C and butane −1°C)

[10]

Q35.IR

Extended response

Absorption at 3360 cm–1 shows OH alcohol presentDeduction of correct structure without explanation scores maximum of 4 marks as this does not show a clear, coherent line of reasoning.

M11

NMR

There are 4 peaks which indicates 4 different environments of hydrogenMaximum of 6 marks if no structure given OR if coherent logic not displayed in the explanations of how two of OH, CH3 and CH2CH3 are identified.

M21

The integration ratio = 1.6 : 0.4 : 1.2 : 2.4

The simplest whole number ratio is 4 : 1 : 3 : 6M3

1

The singlet (integ 1) must be caused by H in OH alcoholM4

1

The singlet (integ 3) must be due to a CH3 group with no adjacent HM5

1

Quartet + triplet suggest CH2CH3 groupM6

1

Integration 4 and integration 6 indicates two equivalent CH2CH3 groupsM7

1

 M8

1[8]