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Alkenes - Addition Polymers - Mark schemes

Q1.(a) P 3,3−dimethylbut−1−ene

ORaccept 3,3−dimethylbutene

Ignore absence of commas, hyphens and gapsRequire correct spelling

Q 3−chloro−2,2−dimethylbutaneOR

accept 2−chloro−3,3−dimethylbutaneIn Q, “chloro” must come before “dimethyl”

2

(b) M1 Electrophilic addition

M2 must show an arrow from the double bond towards the H atom of HClM3 must show the breaking of the H−Cl bondM4 is for the structure of the carbocationM5 must show an arrow from the lone pair of electrons on the negatively charged chloride ion towards the positively charged carbon atom on their carbocation.

NB The arrows here are double−headedM1 both words requiredFor the mechanismM3 Penalise incorrect partial charge on H−Cl bond and penalise formal chargesIgnore partial negative charge on the double bond.Maximum 3 of 4 marks for a correct mechanism using HBr or the wrong organic reactant or wrong organic product (if shown) or a primary carbocationPenalise once only in any part of the mechanism for a line and two dots to show a bondCredit the correct use of “sticks”For M5, credit attack on a partially positively charged carbocation structure, but penalise M4

5

(c) M1 Nucleophilic substitutionFor M1, both words required.Accept phonetic spelling

M2 must show an arrow from the lone pair of electrons on the nitrogen atom of an ammonia molecule to the correct C atomM3 must show the movement of a pair of electrons from the C− Cl bond to the Cl atom. Mark M3 independently provided it is from their original moleculeM4 is for the structure of the alkylammonium ion, which could be a condensed formula. A positive charge must be shown on, or close to, the N atom.M5 is for an arrow from the N−H bond to the N atomAward full marks for an SN1 mechanism in which M2 is the attack of the ammonia on the intermediate carbocation

NB These are double-headed arrowsFor the mechanismPenalise M2 if NH3 is negatively charged.Penalise M3 for formal charge on C of the C−Cl or incorrect partial charges on C−ClPenalise M3 for an additional arrow from the Cl to something elseThe second mole of ammonia is not essential for M5; therefore ignore any species herePenalise once only for a line and two dots to show a bondMaximum 3 of 4 marks for the mechanism for wrong organic reactant OR wrong organic product if shownAccept the correct use of “sticks”

5

(d) M1 (base) eliminationM1 Dehydrohalogenation

M2 KOH OR NaOHM3 Must be consequential on a correct reagent in M2, but if incomplete or inaccurate attempt at reagent (e.g. hydroxide ion), penalise M2 only and mark on

Any one from• high temperature OR hot OR heat / boil under reflux• concentrated• alcohol / ethanol (as a solvent) / (ethanolic conditions)

M3 not “reflux” aloneM3 if a temperature is stated it must be in the range 78C to 200 °CIgnore “pressure”

3

(e) M13NaBr + H3PO4 3HBr + Na3PO4

M1 Credit correct ionic species in the equation

M2 and M3SO2 and Br2 identifiedM4Concentrated sulfuric acid• is an oxidising agent• oxidises the bromide (ion) or Br − or NaBr or HBr • is an electron acceptor

In M2 and M3 the two gases need to be identified. If equations are used using sulfuric acid and the toxic gases are not identified clearly, allow one mark for the formulas of SO2 and Br2

• apply the list principle as appropriate but ignore any reference to HBr• the marks are for identifying the two gases either by name or formula

4[19]

Q2.(a) Electrophile: e– pair / lone pair acceptor or e– deficient species or e–

seeking species (1)For ‘species’ accept atom, molecule, ionNOT ‘+’ ionNOT ‘attracted to ‘- ’ charge’

Addition: reaction which increases number of substituents orconvert double bond to single bond or where two moleculesform one molecule (1)

2

(b) (High) e– dense or e– rich C=C or e– rich π bond or 4 e– between the C’s (1)NOT just ‘C=C’

causes induced dipole in Br2 (1)Ignore refs to ‘temporary’can score M2 from δ+ / δ– on Br2 in (c) unless a contradicting error in (b)

2

(c) Mechanism:

If incorrect alkene, lose M3 (wrong cation)Mark M4 conseq on M3

Name of product: 1,2-dibromopropane (1)5

(d) addition (1)

Not additional1

[10]

Q3.(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]

Q4.(a) (i) Reagent: Hydrogen of H2 (1)

Conditions: Ni (catalyst) (Ignore Pt) (1)100 – 200 °C or heat (1)

Not ‘high temp’ or ‘warm’M1 = 0, M2 = 1 then M3 = 0 maxor M1 = M2 = 0 then M3 = 0M3 tied to M1. Only award M3 if M1 earned

(ii) Difference in structure: soft margarine less hydrogenated orhas more C=C bonds or is more unsaturated than hardmargarine (1)Difference in melting point: soft has lower melting point (1)

Must be comparison5

(b) (i) 3-methylbutan-2-ol (1)No alternatives

(ii) elimination or dehydration (1)

(iii) (c) H2SO4 or (c) H3PO4 – name or correct formula (1)

(iv)

Double bond must be shownAccept any correct unambiguous structuresif but- 1-ene and but-2-ene offered, allow M2

5[10]

Q5.

(a) May circle 4 C’s separately

1

(b)

Ignore δ+ and δ- unless wrong

4

(c) Reagent: H2O or water OR steam, Or dilute sulphuric acid (1)Condition: heat, or warm, or boil or reflux [50-100°C] (1)Name of compound C: 2-methylbutan-2-ol (1)

Allow 2-methylbutane-2-olPenalise hydroxy-2-methylbutane and 2-methylbut-2-ol once only in the paper

3

(d) Identity of alcohol D: 2-methylbutan-1-ol (1),OR its structure, could describe structure

Explanation: C formed via t-carbocation; D via p-carbocation, (1) tertiary more stable than primary (1)

If have wrong carbocation can still score stability mark3

[11]

Q6.(a) Contains a C=C OR a double bond

1

(b) Electrophilic additionBoth words needed

1

Mechanism:

Ignore partial negative charge on the double bond.M2 Penalise partial charges on bromine if wrong way and penalise formal chargesPenalise once only in any part of the mechanism for a line and two dots to show a bond.

M1 Must show an arrow from the double bond towards oneof the Br atoms on a Br-Br molecule.

Deduct 1 mark for sticks.

M2 Must show the breaking of the Br-Br bond.

M3 Is for the structure of the secondary carbocation with Br substituent.

M4 Must show an arrow from the lone pair of electrons on anegatively charged bromide ion towards the positivelycharged carbon atom.

Deduct 1 mark for wrong reactant, but mark consequentially.If HBr, mark the mechanism consequentially and deduct one markIf but-1-ene, mark the mechanism consequentially and deduct one mark.If both HBr and but-1-ene, mark the mechanism consequentially and deduct ONLY one mark.

4

(c) (i) M1 Compounds with the same structural formulaPenalise M1 if “same structure”Ignore references to “same molecular formula” or “same empirical formula”

1

M2 With atoms/bonds/groups arranged differently in spaceORatoms/bonds/groups have different spatial

arrangements/ different orientation.Mark independently.

1

(ii)

Award credit provided it is obvious that the candidate is drawing the trans isomer.Do not penalise poor C–C bondsTrigonal planar structure not essential

1[9]

Q7.(a) (i)

If wrong carbocation, lose structure markIf wrong alkene, lose structure mark Can still score ¾ i.e. penalise M3Penalise M2 if polarity included incorrectly no bond between H and Br bond is shown as or

(ii) credit secondary carbocation here if primary carbocation has been used in (i)

Ignore attack on this carbocation by 5

(b) (i) Structure:

No credit for propan-1-ol even when named correctlyCredit propane-2-ol

Name: propan-2-ol (1)Not 2-hydroxypropane

(ii) Name of mechanism: nucleophilic substitution (1) (both words)(NOT SN1 orSN2)

Mechanism:

penalise incorrect polarity on C-Br (M1)Credit the arrows even if incorrect haloalkaneIf SN1, both marks possible

5

(c) (i) elimination (1)Ignore nucleophylic eliminationPenalise electrophilic elimination

(ii) base (1)OR proton acceptorNOT nucleophile (base)

2[12]

Q8.(a)

1

1

NB The bonds shown in the structure must be correct

Isomerism: E-Z isomerismIf written answer is correct, ignore incorrect labelling of structures.If no written answer, allow correctly labelled structures.

1

Both COOH groups must be on the same side/ close together/ cis1

No rotation about C=C axis1

Structure

1

(b) Br2 / HBr / H2SO4 / H+ / Br+ / NO2+ (Mark M1)

NB If electrophile H+ / Br+ / NO2

+ allow M1, M2 and M4 If the acid is incorrect, M2 and M3 can still be scored Allow M4 consequentially if repeat error from part (a)

4

(c) e.g. 2NaOH + HO2CCHCHCO2H → NaO2CCHCHCO2Na + 2H2O

Both H replaced1

Balanced for atoms and charges1

NB Allow ionic equations and 2NaOH + C4H4O4 → C4H2O4Na2+ 2H2O Allow one if structure incorrect but molecular formula correct Allow one for a correct equation showing one H replaced

(d) M1 Two peaks1

M2 No splitting or singlets1

M3 (Two) non-equivalent protons or two proton environments1

M4 No adjacent protons1

M5 Same area under the two peaks or same relative intensity1

NB Doublet could score M1 and M3 or M5 (Max 2) More than two peaks CE = 0 Apply the “list principle” to incorrect answers if more than 3 given

Max 3[15]

Q9.(a) (i) An appropriate alkene; CH3CH2CHCH2 or (CH3)2CCH2

1

Isomer 11

Isomer 21

Position isomerism1

Mechanism

electrophilic attack and electron shift to Br (Unless H+ used)1

carbocation1

reaction with carbocation[Allow mechanism marks for the alkene CH3CHCHCH3][Allow one mark if mechanism for minor product given]

1

(ii) An appropriate carbonyl; CH3CH2CHO1

Mechanism nucleophilic attack and electron shift to O1

anion intermediate1

reaction with anion[Allow mechanism marks for the carbonyl (CH3)2CO]

1

Isomer 11

Isomer 21

Optical isomerismNB Isomer structures must be tetrahedralNB Penalise “stick” structures once in part (a)

1

(b) QoL

Large charge on carbonyl carbon atom due to bondingto O and Cl

1

Nucleophiles have electron pairs which can be donated1

Equation Species1

Balanced1

[18]

Q10.(a) (i) Electrophilic addition

(Both words required)1

(ii) M1 the reaction to form 1-bromopropane goes via the primarycarbocation OR 1o carbocation

OR via

M2 primary carbocations are less stable than secondary carbocations(Credit converse arguments for M1 and M2 i.e. the reaction to form 2-bromopropane goes via the secondary carbocation , M1, and secondary carbocations are more stable than primary carbocations, M2)(Accept the use of “carbonium ions” as an alternative to carbocation)

1

(b) M1 NaOH OR KOH OR correct name1

M2 aqueous or solution in water (ignore heat, reflux etc.)(Penalise M1 for hydroxide ion alone, but mark on and credit M2)(Credit M2 ONLY for H2O as reagent and heat / warm / T=50 to 100oC)(NaOH(aq) scores M1 and M2 provided it is not contradicted)(Penalise M2 if NaOH(aq) followed by concentrated or ethanol)(Penalise M1 and M2 if followed by acid)

1

(c) Ethanolic OR alcoholic OR CH3CH2OH / CH3OH solvent ORaqueous ethanol/alcoholOR higher temperature (must be comparative)

(Ignore heat or heat under reflux)(Credit part (c) independently from part (b))(Penalise “ethanoic”)

1

(d) (i) Secondary OR 2o

1

(ii)

M1 arrow from double bond to H of H – O bondM2 arrow from bond to oxygen atom to show H – O bond breakageM4 arrow from lone pair of electrons to carbon atom of carbocation

(Penalise M1 if arrow goes to H2SO4 or to formal positive charge on H, but ignore partial charges on sulphuric acid unless wrong)(Credit M2 for H+ ion)(For M4, accept negative charge anywhere on the ion)

4

(iii) Catalyst ONLY(Ignore homogeneous, heterogeneous)

1[12]

Q11.(a) (i)

If wrong carbocation, lose structure markIf wrong alkene, lose structure markCan still score ¾ i.e. penalise M3Penalise M2 if polarity included incorrectlyno bond between H and Brbond is shown as or

4

(ii) CH3CH2CH2

credit secondary carbocation here if primary carbocation hasbeen used in (i)

Ignore attack on this carbocation by o1

(b) (i) Structure: 1

Name: propan-2-olNot 2-hydroxypropane

1

(ii) Name of mechanism: nucleophilic substitution (both words)(NOT SN1 or SN2)

1

Mechanism:

penalise incorrect polarity on C-Br (M1)Credit the arrows even if incorrect haloalkaneIf SN1, both marks possible

2

(c) (i) elimination1

(ii) baseOR proton acceptorNOT nucleophile

1[12]

Q12.(a) M1 curly arrow from lone pair on oxygen of hydroxide ion to

H atom on C-H adjacent to C-Br1

M2 curly arrow from single bond of adjacent C-Hto adjacent single bond C-C

(only credit M2 if M1 is being attempted to correct H atom)1

M3 curly arrow from C-Br bond to side of Br atom(credit M3 independently)

1

(b) Ml credit a correct structure for either geometrical E-Z isomer and itsdesignation as either cis or trans.OR credit two correct geometrical E-Z isomer structures(ignore the names)OR credit two correct names for cis pent-2-ene and transpent-2-ene (ignore the structures)

1

M2 credit a second mark if all four parts of the required structures andnames are correct.

(credit “linear” structures)(insist on the alkyl groups being attached clearly by C-C bonds)

1

(c) (i) Ml curly arrow from middle of C = C bond to H atom on H-Br(penalise M1 if partial negative charge or formal positive

charge on H)(penalise Ml if pent-2-ene is used)

1

M2 curly arrow from H-Br bond to side of Br atom1

M3 correct structure for correct secondary carbocation1

M4 curly arrow from lone pair on bromide ion to the positivecarbon of carbocation, ensuring that bromide ion has anegative charge.

(with the exception of pent-2-ene, if the wrong alkene is used, only penalise the structure M3)(penalise the use of two dots in addition to a covalent bond, once only)

1

(ii) 1-bromopentane1

(iii) Ml 2-bromopentane is formed via the secondary (or 2°)carbocation

1

OR 1-bromopentane is formed via the primary (or 1°)carbocationM2 a secondary carbocation is more stable than a primarycarbocation -award this mark only if the quality of language justifiesthe award.

(the argument must involve clear statements about carbocations)

1[12]

Q13.(a) hydration OR (electrophilic) addition

(penalise incorrect words in front of the word “addition” e.g. “nucleophilic”)(penalise “indirect hydration” but credit “direct hydration” or “steam hydration”)

1

H2C=CH2 + H2O → CH3CH2OH(ignore state symbols)(credit use of C2H5OH for ethanol) (penalise use of C2H6O for ethanol on the first occasion)(credit C2H4 and CH2=CH2 for ethene) (penalise CH2CH2, CH2.CH2, CH2:CH2 for ethene on the first occasion)(ignore H2SO4 OR extra H2O OR H+ if it appears on both sides)

1

conc. H2SO4 OR conc. H3PO4

1

(b) (i) Carbon OR C(credit “soot” or “sooty”)(penalise “coke” or “coal”)(credit “carbon + carbon monoxide” provided it is clear that carbon is solid; penalise “carbon + carbon dioxide”)

1

(ii) CH3CH2OH + O2 → 2C + 3H2OORCH3CH2OH + 1½O2 → C + CO + 3H2O

(credit multiples of these equations)(credit use of C2H5OH for ethanol)(penalise use of C2H6O for ethanol, but note a possible repeat error from part (a) above)

1[5]

Q14.(a) M1 C6H12O6 2CH3CH2OH + 2CO2

(2C2H5OH)Mark independentlyFor M1 and M3 ignore state symbols and credit multiplesFor M1 and M3 penalise C2H6O once only

M2 fermentation

M3 CH3CH2OH + 3O2 2CO2 + 3H2O (C2H5OH)

M4 A specified process e.g. planting / harvesting / transport / extracting sugar / distilling ethanol solution / fertiliser production etc.

M5 The specified process uses / burns (fossil) fuel that releases CO2

For M5, “releases / increases carbon emissions” is insufficient as an alternative to releases CO2

5

(b) M1 sodium or potassium hydroxide / NaOH / KOHMark on to M2 from hydroxide ion

M2 depends on correct M1Ignore OH– if KOH/ OH–

warm / heat / reflux and aqueous or (aq) or waterFor M2 ignore “dilute”For M2 penalise T > 100 °C

M3 nucleophilic substitutionAcidified KOH/NaOH or H2SO4 with KOH/NaOH loses M1 and M2

For M3, both words required

NB The arrows here are double-headed

M4 must show an arrow from the lone pair of electrons on the oxygen atom of the negatively charged hydroxide ion to the C atom.

Penalise M4 if covalent NaOH / KOH is usedPenalise one mark from M4 or M5 if half-headed arrows are used

M5 must show the movement of a pair of electrons from the

C— Br bond to the Br atom. Mark M5 independently provided it is from their original molecule.

Penalise M5 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 M4 and M5, award full marks for an SN1 mechanismFor M4 and M5, maximum 1 of 2 marks if wrong reactant is used.Penalise M5 if an extra arrow is drawn from the Br of the C–Br bond to, for example, K+

Do not penalise the use of “sticks”

M6 One statement from

• The yield is (very) low / not a high yield OR elimination occurs / ethene formed

• The rate of reaction slow

• Bromoethane has to be manufactured / made first

• Bromoethane is expensiveFor M6 ignore references to other costs and expenses

6

(c) M1 concentrated phosphoric acid / conc. H3PO4 OR concentrated sulfuric acid /conc. H2SO4

Answers in any orderIgnore reference to support medium in M1

M2 hydration or (electrophilic) addition

For M3 and M4 any two fromDo not apply the list principle to these three chosen criteria in M3 and M4

• Excess ethene

OR Excess steam / water / H2O

OR remove the ethanol as it forms

OR recycle the ethene

• Specified Pressure

50 atm ≤ P ≤ 100 atm

OR 5000 kPa ≤ P ≤ 10000 kPa

OR 5 MPa ≤ P ≤ 10 MPa

• HighTemperature unless they give a value that is not in the ranges given here;

OR 300 °C ≤ T ≤ 600 °C

OR 570 K ≤ T ≤ 870 KAccept a reference to “low temperature” if they specify a correct temperature range or a correct temperature in the range

4[15]

Q15.(a) M1 Cl2 (provides the pale green colour)

M1 requires the formula

M2 NaOH reacts with the acid(s)/the HCl/the HClO/H+

Ignore “reacts with the products”Ignore “reacts with chloride ion”Ignore “reacts with chlorine”

M3 requires a correct answer in M2Equilibrium shifts (from left ) to right OR wtte

3

(b) M1 A reducing agent is an electron donor OR (readily) loses/gives away electrons

Penalise M1 if “electron pair donor”

M2 Cl2 + 2e– → 2Cl–

For M3 and M4, iodide ions are stronger reducing agents thanchloride ions, because

Ignore state symbols in M2 Accept no charge on the electronCredit the electrons being lost on the RHS

M3 Relative size of ions/atomic radius/ionic radiusIodide ions are larger/have more (electron) shells/levels thanchloride ions (or converse for chloride ion) OR electron(s) to belost/outer shell/level is further from the nucleus (or converse forchloride ion) OR greater/more shielding

For M3 insist on “iodide ions”

M4 Strength of attraction for electron(s) being lostElectron(s) lost from an iodide ion is less strongly held by the nucleus

compared with that lost from a chloride ionM3 and M4 must be comparative and should refer to electrons.

(assume argument refers to iodide ions but accept converse argumentfor chloride ions)

4

(c) M1 2Cl2 + 2H2O → 4HCl + O2

Or multiples

M2 silver chloride ONLYM2 requires a name

M3 The solid/precipitate would dissolveOR is solubleOR (It) forms a (colourless) solution

Mark M3 independentlyIgnore “disappears”

3

(d) Electrophilic addition1

Mechanism:

M2 Penalise partial charges if wrong way around, otherwise ignoreMax 3 marks for the mechanism for wrong reactant and/or “sticks” (wrong reactant could be HBr or Br2 or incorrect alkene)

M1 must show an arrow from the double bond towards one of theCl atoms on a Cl–Cl molecule.

M2 must show the breaking of the Cl–Cl bond.

M3 is for the structure of the carbocation with Cl substituent.

M4 must show an arrow from the lone pair of electrons on a negativelycharged chloride ion towards the positively charged carbon atom.

4[15]

Q16.(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]

Q17.(a) M1 Benzene is more stable than cyclohexatriene

more stable than cyclohexatriene must be stated or impliedIf benzene more stable than cyclohexene, then penalise M1 but mark onIf benzene less stable: can score M2 only

1

M2 Expected ΔHο hydrogenation of C6H6 is 3(–120)

= –360 kJ mol-1

Allow in words e.g. expected ΔHο hydrog is three times the ΔHο hydrog of cyclohexene

1

M3 Actual ΔHο hydrogenation of benzene is

152 kJ mol-1 (less exothermic)

or 152 kJ mol-1 different from expectedIgnore energy needed

1

M4 Because of delocalisation or electrons spread out or resonance1

(b) No mark for name of mechanism

Conc HNO3

If either or both conc missing, allow one;1

Conc H2SO4

this one mark can be gained in equation1

2 H2SO4 + HNO3 → 2 HSO4– + NO2

+ + H3O+

OR

H2SO4 + HNO3 → HSO4– + NO2

+ + H2O

OR via two equations

H2SO4 + HNO3 → HSO4– + H2NO3

+

H2NO3+ → NO2+ + H2O

Allow + anywhere on NO2+

1

M1 arrow from within hexagon to N or + on NAllow NO2

+ in mechanismhorseshoe must not extend beyond C2 to C6 but can be smaller+ not too close to C1M3 arrow into hexagon unless Kekuleallow M3 arrow independent of M2 structureignore base removing H in M3+ on H in intermediate loses M2 not M3

3

(c) If intermediate compound V is wrong or not shown, max 4 for 8(c)

or chlorocyclohexane or bromocyclohexane1

Reaction 3

M2 HBr1

M3 Electrophilic additionAllow M2 and M3 independent of each other

1

Reaction 4

M4 Ammonia if wrong do not gain M51

Allow M4 and M6 independent of each other

M5 Excess ammonia or sealed in a tube or under pressure1

If CE e.g. acid conditions, lose M4 and M5

M6 Nucleophilic substitution

1

(d) Lone or electron pair on NNo marks if reference to “lone pair on N” missing

1

Delocalised or spread into ring in U1

Less available (to accept protons) or less able to donate (to H+)1

[19]

Q18.(a) (i) (Free-) radical substitution

Both words needed1

(ii) UV light/Ultra-violet light/sunlightOR high temperature/150 °C ≤ T ≤ 500 °C

1

(iii) Propagation (Step)Ignore “first” or “second”Accept phonetic spelling

1

(iv) M1 Termination (Step)

M2 2CH3CH2CH2• C6H14

In M2C6H14 may be drawn out as CH3CH2CH2CH2CH2CH3

The dot may be anywhere around the terminal CH2 on the radicalAccept C3H7• with dot anywherePenalise the absence of any radical dot

2

(v) C3H8 + 8Br2 C3Br8 + 8HBrOr multiples

1

(b) (i) M1 Double bonds are

electron-rich

OR electron pair donors

OR centres of electron density.

M2 Bromine becomes polarised/becomes polar

OR forms an induced dipole

OR becomes δ+/δ–M1 QoL – require one of these termsIgnore “(very) negative” and “nucleophile” as applied to the double bond.

Penalise M2 for ion formation from bromineFor M2, do not credit dipole formation solely as a consequence of electronegativity

2

(ii) Electrophilic additionBoth words neededAccept phonetic spelling

1

(iii) Structure for 1,2,4,5-tetrabromopentane, for exampleBrCH2CHBrCH2CHBrCH2Br

OR

Must be clear that they have drawn 1,2,4,5-tetrabromopentane and does NOT need to be displayedCredit use of “sticks” for each C-H bond

1

(c) +

M1 Structure of CH3CHCH3

M2 (Secondary) Carbocation OR (secondary) carbonium ionsMark independentlyFor M1 the positive charge must be on the central carbon atomPenalise bond to positive chargePenalise answers which show more than the correct carbocation e.g. the mechanism, unless the intermediate is clearly identifiedCredit use of “sticks” for each C-H bondFor M2, penalise “primary” or “tertiary”

2[12]

Q19.(a) (i) M1 Elimination

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

M3 must show an arrow from a C-H bond adjacent tothe C-Br bond towards the appropriate C-C bond.Only award if a reasonable attempt has been madeat the attack on the H atom of the appropriate adjacent C-H

M4 is independent provided it is from their original molecule

Award full marks for an E1 mechanism in which M3 is on the correct carbocation.

N.B. These are double-headed arrowsFor M1, accept “Base elimination” but no other prefix.Penalise M2 if covalent KOHPenalise M4 for formal charge on C of C-Br or incorrect partial charges on C-BrIgnore other partial chargesPenalise once only in any part of the mechanism for a line and two dots to show a bond.Max any 2 of 3 marks for the mechanism for wrong reactant (or wrong product if shown).Accept the correct use of “sticks” for the molecule except for the C-H being attacked

4

(ii) Structure for pent-1-ene

CH3CH2CH2CH=CH2

Penalise C3H7

Accept correct “sticks”1

(b) M1 Electrophilic addition

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

M3 must show the breaking of the Br-Br bond.

M4 is for the structure of the tertiary carbocation with Br on the correct carbon atom.

M5 must show an arrow from the lone pair of electrons on the negatively charged bromide ion towards the positively charged carbon atom.

N.B. These are double-headed arrowsFor M1, both words required.For the mechanismM2 Ignore partial negative charge on the double bond.

M3 Penalise partial charges on Br-Br bond if wrong way and penalise formal chargesPenalise once only in any part of the mechanism for a line and two dots to show a bondMax any 3 of 4 marks for the mechanism forwrong organic reactant or wrong organic product (if shown) or primary carbocation.If HBr is used, max 2 marks for their mechanismAccept the correct use of “sticks”

5

(c) M1 Nucleophilic substitution

M2 must show an arrow from the lone pair of electrons on the nitrogenatom of an ammonia molecule to the C atom.

M3 must show the movement of a pair of electrons from the C-Br bondto the Br atom. M3 is independent provided it is from their original molecule

M4 is for the structure of the alkylammonium ion, which could be acondensed formula. A positive charge must be shown on/or close to,the N atom.

M5 is for an arrow from the N-H bond to the N atom.

Award full marks for an SN1 mechanism in which M2 is the attackof the ammonia on the intermediate carbocation.

N.B. These are double-headed arrowsFor M1, both words required.Penalise M2 if NH3 is negatively charged.Penalise M3 for formal charge on C or incorrect partial chargesThe second mole of ammonia is not essential for M5; therefore ignore any species here.Penalise once only for a line and two dots to show a bond.Max any 3 of 4 marks for the mechanism for wrong organic reactant (or wrong organic product if shown)Accept the correct use of “sticks”

5[15]

Q20.(a) (i) Structure of (Z)-but-2-enenitrile with or without either or both of the CH3 and

the CN groups displayed

Penalise C−NCDo not penalise C−H3CIgnore bond angles.

1

(ii) Restricted rotation / no (free) rotation about the double bond / about the C=C OR does not rotate (about the double bond)

Must use the word rotate / rotation.1

(b) Repeating unit of polyalkene

All the bonds relevant to the unit must be drawn out including those on either side of the unit. There is no need to expand either the CH3 or the CNPenalise C−NCPenalise “sticks”.Ignore brackets.Penalise “n”

1

(c) Feature 1Absorption / peak in the range 2220 to 2260 cm−1 or specified value in this range or marked correctly on spectrumand(characteristic absorption / peak for) C≡N / CN group / nitrile / cyanide group

Allow the words “dip” OR “spike” OR “trough” OR “low transmittance” as alternatives for absorption.Allow a peak at 2200 cm−1 to 2220 cm−1 in this case.

Feature 2Absorption / peak in the range 1620 to 1680 cm−1 or specified value in this range or marked correctly on spectrumand(characteristic absorption / peak for) C=C group / alkene / carbon-carbon double bond

Ignore reference to other absorptions eg C-HEither order.

2[5]

Q21.(a) Position(al) (isomerism)

1

(b)

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

M1 must show an arrow from the double bond towards the H atom of the H–Br molecule

M1 Ignore partial negative charge on the double bond.

M2 must show the breaking of the H–Br bond.M2 Penalise partial charges on H–Br bond if wrong way and penalise formal charges

M3 is for the structure of the secondary carbocation.Penalise M3 if there is a bond drawn to the positive charge

M4 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 primary or secondary carbocation.

Penalise once only in any part of the mechanism for a line and two dots to show a bondMaximum any 3 of 4 marks for wrong reactant or primary carbocation.If Br2 is used, maximum 2 marks for their mechanismDo not penalise the use of “sticks”

NB The arrows here are double-headed4

(c)

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

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

Penalise M1 if covalent KOH

M2 must show an arrow from a C–H bond adjacent to the C–Br bond towards the appropriate C–C bond. Only award if an arrow is shown attacking the H atom of an adjacent C–H (in M1)

M3 is independent provided it is from their original molecule.Penalise M3 for formal charge on C of the C–Br or incorrect partial charges on C–BrPenalise M3 if an extra arrow is drawn from the Br of the C–Br bond to, for example, K+

Ignore other partial chargesPenalise once only in any part of the mechanism for a line and two dots to show a bond.Maximum any 2 of 3 marks for wrong reactant or wrong product(if shown) or a mechanism that leads to but-1-eneAccept the correct use of “sticks” for the molecule except for the C–H being attacked



[8]

Q22.(a) (i)

Penalise one mark from their total if half-headed arrows are usedPenalise M3 for formal charge on C of the C-Br or incorrect partial charges on C-BrIgnore other partial charges

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

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

M2 must show an arrow from the correct C–H bond to the correct C–C bond.Only award if an arrow is shown attacking the H atom of the correct C–Hbond in M1

M3 is independent but CE=0 if nucleophilic substitution

N.B these are double-headed arrows3

(ii)

Award 1 mark if both correct stereoisomers but in the wrong placesAccept no other alkenes.Be reasonably lenient on the bonds to ethyl (or to CH2CH3) since the question is about E and Z positions but penalise once only if connection is clearly to the CH3 of CH2CH3

Accept linear structures2

(iii) M1 (Compounds / molecules with) the same structural formulaPenalise M1 if “same structure”

M2 with atoms/bonds/groups arranged differently in spaceIgnore references to “same molecular formula” or “same empirical formula” or any reference to “displayed formula”

ORatoms/bonds/groups that have different spatial arrangements / different orientation.Mark independently

2

(b)

M1must show an arrow from the double bond towards the H atom of the H – O bond

OR HO on a compound with molecular formula for H2SO4

M1 could be to an H+ ion and M2 an independent O – H bond break on a compound with molecular formula for H2SO4


M2 must show the breaking of the O – H bond.M2 Penalise partial charges on O – H bond if wrong way and penalise formal chargesIn M2 do not penalise incorrect structures for H2SO4

M3 is for the structure of the carbocation.

M4 must show an arrow from the lone pair of electrons on the correct oxygen of the negatively charged ion towards a correct (positively charged) carbon atom.

M4 NOT HSO4–

For M4, credit as shown or –: OSO 3H ONLY with the negative charge anywhere on this ion

OR correctly drawn out with the negative charge placed correctly on oxygenPenalise once only in any part of the mechanism for a line and two dots to show a bond

NB The arrows here are double-headedMax 3 of any 4 marks for wrong organic reactant or wrong organic product (if shown)Accept the correct use of “sticks”

4[11]

Q23.(a) M1 electrophilic addition

For M1, both words requiredAccept phonetic spelling

For the mechanismM2 Ignore partial negative charge on the double bond


M3 Penalise partial charges on H–Br bond if wrong way and penalise formal charges

M3 must show the breaking of the H–Br bondPenalise 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 correct (positively charged) carbon atom

Maximum any 3 of 4 marks for the mechanism for wrong (organic) reactant OR wrong organic product (if shown) OR primary carbocationAccept the correct use of sticks

NB These are double-headed arrows5

(b) M1 Nucleophilic substitutionFor M1, both words requiredAccept phonetic spelling

For the mechanismPenalise M2 if NH3 is negatively charged

M2 must show an arrow from the lone pair of electrons on the nitrogen atom of an ammonia molecule to the correct C atom

Penalise M3 for formal charge on C of the C−Br or incorrect partial charges on C−BrPenalise M3 for an additional arrow from the Br to something else

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

The second mole of ammonia is not essential for M5; therefore ignore any species here

M4 is for the structure of the alkylammonium ion, which could be a condensed formula. A positive charge must be shown on / or close to, the N atom

Penalise once only for a line and two dots to show a bond

M5 is for an arrow from the N–H bond to the N atomMaximum any 3 of 4 marks for the mechanism for wrong organic reactant OR wrong organic product if shown

Award full marks for an SN1 mechanism in which M2 is the attack of the ammonia on the intermediate carbocation

Accept the correct use of “sticks”


(c) M1 (addition) polymerisation OR poly-additionIgnore “additional”Credit polyprop-1-ene and polypropylene

M2 poly(propene) / polypropenePenalise “condensation polymerisation”

2

(d)


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

Penalise M3 for formal charge on C of C–Br or incorrect partial charges on C−Br.

M2 must show an arrow from a correct C–H bond adjacent to the C–Br bond to the appropriate C–C bond. Only award if an arrow is shown attacking the H atom of a correct C−H bond in M1

Ignore other partial chargesPenalise once only in any part of the mechanism for a line and two dots to show a bond

M3 is independent provided it is from their original molecule, but CE=0 if nucleophilic substitution

Maximum any 2 of 3 marks for wrong organic reactant


Accept the correct use of “sticks” for the molecule except for the C–H being attacked


[15]

Q24.

(a)

M1, M2 and M4 are awarded for the three curly arrows shown on the mechanism (1 mark for each correct)

M3 is for the structure of the carbocation intermediate4

(b) Correct answers include:• the displayed formula• structural formulae such as CH3CH(CH3)CH(OSO3H)CH3

• skeletal formulae such as

1

(c) The major product is formed via a tertiary carbocation intermediate and the minorproduct is formed via a secondary carbocation intermediate

1

The tertiary carbocation is more stable than the secondary carbocation1

[7]

Q25.(a) Structure for 3-methylbut-1-ene

H2C=CHCH(CH3)2

Any correct structural representation.Credit “sticks” and require the double bond.

1

(b) Structure for 2-methylpropan-2-ol

(CH3)3COHAny correct structural representation.Credit “sticks”.

1

(c) Structure for propene

H2C=CHCH3

Any correct structural representation.Credit “sticks” and require the double bond.

1

(d) Structure for 2-aminobutane

CH3CH2CH(NH2)CH 3

Any correct structural representation.

Credit “sticks”.1

[4]

Q26.(a) (i) M1 (Yield) increases / goes up / gets more

If M1 is blank, mark on and seek to credit the correct information in the explanation.If M1 is incorrect CE=0 for the clip.

M2The (forward) reaction / to the right is exothermic or gives out / releases heat OR The reverse reaction / to the left is endothermic or takes in / absorbs heatM3 depends on a correct statement for M2

M3 depends on correct M2 and must refer to temperature / heatThe (position of ) equilibrium shifts / moves left to right to oppose thedecrease in temperatureFor M3, the equilibrium shifts / movesto release heat ORto raise the temperature ORto heat up the reaction.

3

(ii) M1 Concentration(s) (of reactants and products) remain or stay constant / the same

For M1 credit [ ] for concentration.

M2 Forward rate = reverse / backward rateNot “equal concentrations”.Not “concentrations is / are the same”.Not “amount”.Ignore “dynamic” and ignore “speed”.Ignore “closed system”.It is possible to score both marks under the heading of a single feature.

2

(b) KBr + H2SO4 KHSO4 + HBrCredit this equation in its ionic form.Ignore state symbols.Credit multiples.

1

(c) M1 SO2 identified

M2 correctly balanced equation (would also gain M1)Credit M2 equation in its ionic form.Ignore state symbols.

2HBr + H2SO4 Br2 + SO2 + 2H2O

Credit multiples.Not H2SO3 on the right-hand side.

Mark M3 independentlyM3 Oxidising agent OR electron acceptor OR oxidantOR to oxidise the bromide (ion) / HBr

M3 Not “electron pair acceptor”.3

(d) (i) M1 Electrophilic addition

M1 both words required.For the mechanismM3 Penalise incorrect partial charges on O − H bond and penalise formal chargesIgnore partial negative charge on the double bond.M5 Not HSO4

–

For M5, credit as shown or −: OSO 3H ONLY with the negative charge anywhere on this ionOR correctly drawn out with the negative charge placed correctly on oxygen.

M2 must show an arrow from the double bond towards the H atom of the H − O bond / HO on a compound with molecular formula for H2SO4

M2 could be to an H+ ion and M3 an independent O − H bond break on a compound with molecular formula for H2SO4

Max any 3 of 4 marks for a correct mechanism using the wrong organic reactant or wrong organic product (if shown) or a primary carbocation.

M3 must show the breaking of the O − H bond on H2SO4

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 correct oxygen of the negatively charged ion towards the positively charged carbon atom on their carbocation

Credit the correct use of “sticks”.For M5, credit attack on a partially positively charged carbocation structure, but penalise M4


(ii) HydrolysisCredit “(nucleophilic) substitution” but do not accept any other prefix.Credit phonetic spelling.

1

(iii) Catalyst1

[16]

Q27.(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 / colourless

Ignore ‘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.



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”.


(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


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]

Q28.(a) Measured volume would be greater

1

Level in burette falls as tap is filled before any liquid is delivered1

(b) Drop sizes varyAllow percentage error for amount of oil will be large as the amount used is so small

1

(c) Use a larger single volume of oil1

Dissolve this oil in the organic solvent1

Transfer to a conical flask and make up to 250 cm3 with more solvent1

Titrate (25 cm3) samples from the flask1

(d) Stage 1

Mass of oil = 0.92 × (5.0 × 10–2 × 5) = 0.23 (g)1

Mol of oil = 0.23 / 885 = 2.6 × 10–4

1

Extended response calculationTo gain 4 or 5 marks, students must show a logical progression from stage 1 and stage 2 (in either order) to stage 3

Stage 2

Mol bromine = 2.0 × 10–2 × 39.4 / 1000 = 7.9 × 10–4

1

Stage 3

Ratio oil : bromine

2.6 × 10–4 : 7.9 × 10–4

Simplest ratio = 2.6 × 10–4 / 2.6 × 10-4 : 7.9 × 10–4 / 2.6 × 10–4

= 1 : 31

Hence, 3 C=C bondsM5 cannot be awarded unless working for M4 is shown

1[12]

Q29.(a) HBr OR HCl OR H2SO4

Allow HI or HY1

(b) Electrophilic addition1

Allow consequential marking on acid in 12.1 and allow use of HY

4

(c) The major product exists as a pair of enantiomers1

The third isomer is 1-bromobutane (minor product)1

Because it is obtained via primary carbocation1

[9]

Q30.

(a) Must show all 4 groups bonded to C=CAllow CH3− for methyl group; allow C2H5 for ethyl groupAllow correct structure of the style

Allow correct skeletal structure

1

(b) M1 electrophilic addition

NB the arrows here are double-headed1

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

1

M3 must show the breaking of the H-Br bond1

M4 is for the structure of the tertiary carbocation1

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

1

M6 3-bromo-3-methylpentane is formed from 3 y carbocation OR2-bromo-3-methylpentane is formed from 2 y carbocation

1

M7 3 y carbocation more stable than 2 y 1

M2-M5 Penalise one mark from their total if half-headed arrows are usedM2 Ignore partial negative charge on the double bondM3 Penalise incorrect partial charges on H-Br bond and penalise formal chargesPenalise M4 if there is a bond drawn to the positive chargePenalise only once in any part of the mechanism for a line and two dots to show a bondMax 3 of any 4 marks (M2-5) for wrong organic reactant or wrong organic product (if shown) or secondary carbocationMax 2 of any 4 marks in the mechanism for use of bromineDo not penalise the “correct” use of “sticks”For M5, credit attack on a partially positively charged carbocation structure but penalise M4M6 is high demand and must refer to product being formed from/via correct class of carbocationM7 is high demand and must be clear answer refers to stability of carbocations (intermediates) not productsCandidate that states that products are carbocations would lose M6 and M7M6,7 allow carbonium ion in place of carbocation; or a description of carbocation in terms of alkyl groups/ number of carbon atoms joined to a positive C

When asked to outline a mechanism, candidates are expected to draw a mechanism with curly arrows (specification 3.3.1.2). On this occasion only we would allow a detailed description as shown.M2 must describe the movement of a pair of electrons / curly arrow from the C=C towards the H atom of the H-Br moleculeM3 must describe the breaking of the H-Br bond with the bonding pair of electrons moving to the Br / curly arrow from H-Br bond to BrM4 is for the structure of the tertiary carbocation (i.e. positive C bonded to one methyl and two ethyl groups)M5 must describe the movement of a pair of electrons from the Br− ion to the positive C atom of the carbocation / curly arrow from the lone pair of electrons on the negatively charged bromide ion towards the positively charged C atom (of either a secondary or) of a tertiary carbocation

[8]

Q31.(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 M3

If 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



M1 Any soluble bromide including HBr

M2 cream precipitate or cream solid / cream suspension



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)


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


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”


M1 NaOH or KOH

M2 white precipitate or white solid / white suspension


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]

Q32.(a) Electrophilic addition

1

M2 = curly arrow from C=C towards H of H−O on ‘their’ sulfuric acidM3 = curly arrow to break H−OPenalise incorrect dipole/full chargesM4 = intermediateM5 = correct anion, lone pair on correct O and curly arrow from that lone pair to C+ on their carbocationIGNORE position of minus sign unless displayed structureIGNORE product

1111

Major product/propan-2-ol formed via most stable carbocation/carbonium ionsecondary carbocation/carbonium ion more stable (than primary) or reverse argument

M6 for idea of carbocation stabilityThis statement gets M6 and M7NOT stability of alcohols

11

(b) Hot/High T (and High P)ALLOW 200-450 C/473-723 K (Quoted)

1

(SiO2 coated in) phosphoric acid (catalyst)NOT (aq)

1

advantages of fermentation

• Low(er) T and P / lower energy use

• Less use of non-renewable fossil fuels/renewable/sustainable (resources)

• Low(er) equipment/plant/capital costsIGNORE carbon neutralmax 2

11

Disadvantages of fermentation

• Slow(er) reaction

• Low atom economy

• Impure product/extra purification/distillation required

• Batch process/labour intensive/difficult to automate

• Land used for sugar crops (so not available for food crops)IGNORE low yieldMax 2

11

[13]

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