3.2.9 Alkenes. Addition Reactions. 271 minutes. 268 marks. Page 1 of 39

Transcription

1 ..9 Alkenes Addition Reactions 7 minutes 68 marks Page of 9

2 M. (a) Electrophile: e pair / lone pair acceptor or e deficient species or e seeking species () For species accept atom, molecule, ion NOT + ion NOT attracted to - charge Addition: reaction which increases number of substituents or convert double bond to single bond or where two molecules form one molecule () (b) (High) e dense or e rich C=C or e rich π bond or e between the C s () NOT just C=C causes induced dipole in Br () Ignore refs to temporary can score M from δ + / δ on Br in (c) unless a contradicting error in (b) (c) Mechanism: If incorrect alkene, lose M (wrong cation) Mark M conseq on M Name of product:,-dibromopropane () 5 (d) addition () Not additional [0] M. (a) (i) Reagent: Hydrogen of H () Conditions: Ni (catalyst) (Ignore Pt) () C or heat () Not high temp or warm M = 0, M = then M = 0 max or M = M = 0 then M = 0 M tied to M. Only award M if M earned Page of 9

3 (ii) Difference in structure: soft margarine less hydrogenated or has more C=C bonds or is more unsaturated than hard margarine () Difference in melting point: soft has lower melting point () Must be comparison 5 (b) (i) -methylbutan--ol () No alternatives (ii) elimination or dehydration () (iii) (c) H SO or (c) H PO name or correct formula () (iv) Double bond must be shown Accept any correct unambiguous structures if but- -ene and but--ene offered, allow M 5 [0] M. (a) % O =.6 % () If % O not calculated only M available C H O () = 5. =.5 =.5 Ratio: : 0: ( C H 0 O) () If arithmetic error in any result lose M If percentage composition calculation done zero (b) (i) Type of alcohol: Tertiary () Reason: No hydrogen atom on central carbon () Page of 9

4 (ii) Penalise missing bonds / incorrect bonds once per paper (c) (i) Aldehyde () Ignore named aldehydes or their structures, penalise wrong named compound (ii) CH CH CH CH OH + [O] CH CH CH CHO + H O () Balanced () C H 0 O is OK as a reactant [O] can be over arrow C H 7 CHO not accepted for product, but C H 5 CH CHO is OK If use C or C 5 compounds no marks in (ii) C.E of wrong alcohol (iii) Name Butanoic acid () Structure: CH CH CH COOH () mark conseq. or as stated 5 (d) Advantage: Fast reaction OR pure product OR continuous process OR cheap on manpower OR high yield, 00% alcohol () Disadvantage: High technology OR ethene from non renewable source OR expensive equipment not just costly () Not answers based on fermentation Page of 9

5 (e) [8] (a) M. May circle C s separately (b) Ignore δ+ and δ- unless wrong (c) Reagent: H O or water OR steam, Or dilute sulphuric acid () Condition: heat, or warm, or boil or reflux [50-00 C] () Name of compound C: -methylbutan--ol () Allow -methylbutane--ol Penalise hydroxy--methylbutane and -methylbut--ol once only in the paper Page 5 of 9

6 (d) Identity of alcohol D: -methylbutan--ol (), OR its structure, could describe structure Explanation: C formed via t-carbocation; D via p-carbocation, () tertiary more stable than primary () If have wrong carbocation can still score stability mark [] M5. (a) (i) If wrong carbocation, lose structure mark If wrong alkene, lose structure mark Can still score ¾ i.e. penalise M Penalise M 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--ol even when named correctly Credit propane--ol Name: propan--ol () Not -hydroxypropane Page 6 of 9

7 (ii) Name of mechanism: nucleophilic substitution () (both words) (NOT S N ors N ) Mechanism: penalise incorrect polarity on C-Br (M) Credit the arrows even if incorrect haloalkane If S N, both marks possible 5 (c) (i) elimination () Ignore nucleophylic elimination Penalise electrophilic elimination (ii) base () OR proton acceptor NOT nucleophile (base) [] M6. (a) ethan(e)-,-diol OR,-ethan(e)diol () antifreeze () OR production of Terylene / polyester feedstock for polyester / PET NOT surfactant NOT plasticizer NOT solvent NOT de-icer (b) Reaction H O or steam () Reaction O () NOT air Ignore reaction Reaction H O () Reaction 5 NH () For Reaction ; credit dil H SO OR H SO (aq) OR HCl (aq) but NOT steam and NOT NaOH(aq) Page 7 of 9

8 (c) Penalise M incorrect δ+ / δ Penalise δ on alkene (M) Penalise dots on bonds once Penalise M (structure) for use of wrong alkene Penalise M for use of Br (d) Water OR aqueous solution OR (aq) in equation () Yeast OR enzyme/zymase OR T 5 C but T not below 0 C and allow warm N.B. yeast and T=60 con Ignore ph Ignore anaerobic / oxygen Ignore time Ignore pressure M M C 6 H O 6 C H 5 OH (or CH CH OH) + CO Allow C H O if balanced equation M OR M5 needs the use of good English and correct chemistry to gain credit M M: The rate of fermentation is slower () OR The rate of hydration is faster QoL OR (The rate of) fermentation is slow and (the rate of) hydration is fast reference correctly to time rather than rate gains credit M5: The product of fermentation is less pure or lower purity OR The product of hydration is more pure or higher purity OR The product of fermentation is impure and that of hydration is pure OR Specific reference to 0 5% versus 90 00% OR correct reference to higher or lower yield 5 [5] M7. (a) (i) Electrophilic addition (Both words required) Page 8 of 9

9 (ii) M the reaction to form -bromopropane goes via the primary carbocation OR o carbocation OR via (b) (c) M primary carbocations are less stable than secondary carbocations (Credit converse arguments for M and M i.e. the reaction to form -bromopropane goes via the secondary carbocation, M, and secondary carbocations are more stable than primary carbocations, M) (Accept the use of carbonium ions as an alternative to carbocation) M NaOH OR KOH OR correct name M aqueous or solution in water (ignore heat, reflux etc.) (Penalise M for hydroxide ion alone, but mark on and credit M) (Credit M ONLY for H O as reagent and heat / warm / T=50 to 00 o C) (NaOH(aq) scores M and M provided it is not contradicted) (Penalise M if NaOH(aq) followed by concentrated or ethanol) (Penalise M and M if followed by acid) Ethanolic OR alcoholic OR CH CH OH / CH OH solvent OR aqueous ethanol/alcohol OR higher temperature (must be comparative) (Ignore heat or heat under reflux) (Credit part (c) independently from part (b)) (Penalise ethanoic ) Page 9 of 9

10 (d) (i) Secondary OR o (ii) M arrow from double bond to H of H O bond M arrow from bond to oxygen atom to show H O bond breakage M arrow from lone pair of electrons to carbon atom of carbocation (Penalise M if arrow goes to H SO or to formal positive charge on H, but ignore partial charges on sulphuric acid unless wrong) (Credit M for H + ion) (For M, accept negative charge anywhere on the ion) (iii) Catalyst ONLY (Ignore homogeneous, heterogeneous) [] M8. (a) M X is,-dibromoethane only M electrophilic addition (both words needed) M the double bond is a centre of electron density OR electron-rich OR nucleophilic OR a source of an electron pair OR a pi cloud/bond of electrons M a dipole or polarity is induced/created/formed in the Br-Br bond/molecule - award this mark only if the quality of language justifies the award. Page 0 of 9

11 (b) nucleophilic substitution (both words needed) Mechanism M curly arrow from lone pair on oxygen of hydroxide ion to C atom of C-Br Mechanism M curly arrow from C-Br bond to side of Br atom (a possible repeat error here from Question a) (award a maximum of one mark for the wrong haloalkane) (credit an SNl mechanism in which Ml will be a curly arrow from the lone pair on oxygen of the hydroxide ion to the correct positive carbon atom) Y is susceptible to attack by hydroxide ions for one of the following reasons o o o the C-Br bond is polar the carbon atom is partially positive (or shown as such) the carbon atom is electron deficient (c) M oxygen (ignore air ) M silver or silver-based (penalise silver nitrate) M Z is epoxyethane M epoxyethane o has a strained ring structure o has a bond angle of 60 o has a bond angle significantly less than tetrahedral (ignore unstable, has strained bonds, is stressed ) Page of 9

12 (d) C H 6 C H + H (d) Ethane-,-diol is used in antifreeze OR in the manufacture of PET/Terylene/polyester (penalise solvent or plasticiser ) Hazard in Route via X/Y o o bromine is toxic or corrosive sodium hydroxide is corrosive or caustic Hazard in Route via epoxyethane o risk of explosion in reaction o epoxyethane is toxic o epoxyethane is a respiratory irritant o epoxyethane causes neurological damage [5] M9. (a) M fermentation M dehydration or elimination (b) (i) yeast OR zymase OR an enzyme (ii) concentrated sulphuric or phosphoric acid (penalise aqueous or dilute as a contradiction) (c) (i) primary or (ii) sugar or glucose or ethanol is renewable OR ethanol does not contain sulphur-containing impurities OR ethanol produces less pollution or is less smoky or less CO/C (the objective is a positive statement about ethanol) (penalise the idea that ethanol is an infinite source or vague statements that ethanol has less impurities) (penalise the idea that ethanol produces no pollution) Page of 9

13 (e) Addition (ignore self or chain as a preface to addition ) (penalise additional) [8] M0. (a) M curly arrow from lone pair on oxygen of hydroxide ion to H atom on C-H adjacent to C-Br M curly arrow from single bond of adjacent C-H to adjacent single bond C-C (only credit M if M is being attempted to correct H atom) M curly arrow from C-Br bond to side of Br atom (credit M independently) (b) Ml credit a correct structure for either geometrical isomer and its designation as either cis or trans. OR credit two correct geometrical isomer structures (ignore the names) OR credit two correct names for cis pent--ene and trans pent--ene (ignore the structures) M credit a second mark if all four parts of the required structures and names are correct. (credit linear structures) (insist on the alkyl groups being attached clearly by C-C bonds) (c) (i) Ml curly arrow from middle of C = C bond to H atom on H-Br (penalise M if partial negative charge or formal positive charge on H) (penalise Ml if pent--ene is used) M curly arrow from H-Br bond to side of Br atom M correct structure for correct secondary carbocation M curly arrow from lone pair on bromide ion to the positive carbon of carbocation, ensuring that bromide ion has a negative charge. (with the exception of pent--ene, if the wrong alkene is used, only penalise the structure M) (penalise the use of two dots in addition to a covalent bond, once only) (ii) -bromopentane Page of 9

14 (penalise C H 6 O once only in this question) (iii) Ml -bromopentane is formed via the secondary (or ) carbocation OR -bromopentane is formed via the primary (or ) carbocation M a secondary carbocation is more stable than a primary carbocation - award this mark only if the quality of language justifies the award. (the argument must involve clear statements about carbocations) [] M. (a) (i) C 6 H O 6 C H 5 OH + CO ; (ii) Concentrated H SO OR concentrated H PO OR Al O ; (penalise aqueous or dilute as a contradiction) C H 5 OH C H + H O OR C H 5 OH H C = CH + H O; (b) (penalise CH. CH and CH -CH and CH : CH for ethene) Nickel OR Ni OR platinum OR Pt OR palladium OR Pd; Hydrogen OR H ; (c) (i) C 8 H O Only; C 9 H 7 O Only; (empirical formula is not consequential on molecular formula) (ii) (An unsaturated compound) contains (at least) one double bond OR Contains C=C; (must be a positive statement) Page of 9

15 (iii) M: Bromine water OR Br (aq) OR Bromine OR Br ; (penalise bromide water, but mark on) M: decolourised or goes colourless OR from brown/red/orange/yellow to colourless; (Must be colourless not clear for M) (chemical error if no reagent or wrong reagent, loses both marks) (credit KMnO for M, (purple) to colourless for M (if acidified) OR (purple) to brown/brown precipitate (if alkaline or unspecified) (No credit for hydrogen or iodine as reagents) [0] M. (a) (i) Electron pair/ lone pair acceptor OR seeking/bonds with an electron pair (insist on reference to a pair of electrons) (ii) M curly arrow from middle of C=C bond of the alkene towards/ alongside the H atom of the H-Br; (penalise arrows which go towards one of the carbon atoms) (ignore a partial negative charge on the C=C) M curly arrow from H-Br bond to side of Br atom; (penalise M if there are formal charges on HBr or if there are partial charges which are the wrong) (penalise M if the single bond has two dots in addition to the line) M correct structure for carbocation; (penalise M if the positive charge is placed on the end of a bond) (penalise M if any alkene other than ethene is used - all other marks can score) M curly arrow from lone pair on bromide ion to the positive carbon of carbocation, ensuring that bromide ion has a negative charge; Page 5 of 9

16 (b) (i) M Oxygen OR O ; (do not credit air alone, but otherwise ignore) (ii) (iii) M silver OR Ag OR silver-based (penalise silver nitrate) correct structure for epoxyethane; (penalise poorly presented C-O bonds) water OR H O; (credit steam OR H SO (aqueous OR dilute) OR NaOH(aq) OR HCl(aq), OR H PO (aq), but insist that (aq) is included) (do not credit HCl or H SO (concentrated or without water present)) (c) (i) M: potassium cyanide OR KCN OR sodium Cyanide OR NaCN; (ignore conditions - dissolved in (aq) or (alc) or KOH(aq) all work) (penalise HCN) M: propanenitrile; (credit propan--nitrile OR propan nitrile, but not propanitrile) (ii) M: ammonia OR NH ; (iii) (If formula is written, insist that it is correct) (ignore conditions, but penalise acidic) M: ethylamine; (credit aminoethane) M: curly arrow from lone pair on nitrogen of (correct formula for) ammonia towards/alongside C atom of C-Br; (penalise M if formula of ammonia is wrong or has a negative charge or has no lone pair or arrow is from negative charge) M: curly arrow from C-Br bond towards/alongside side Br atom; (credit M independently) (penalise M if formal positive charge on C atom of C-Br) Page 6 of 9

17 M: correct structure of the ethylammonium ion; (credit the structure drawn out with all four bonds around the nitrogen atom OR written as C H 5 NH + OR CH CH NH + ) M: curly arrow from the middle of one of the H-N bonds towards the positive N atom; (possible to credit M on an incorrect ethylammonium ion with no positive charge) (ignore use of ammonia or bromide ion etc. to remove proton from ethylammonium ion) (If the wrong haloalkane is used, award MAX. marks for the mechanism) (If S N mechanism is used, give full credit in which M is for a curly arrow from the lone pair of the N atom of (correct formula for) ammonia towards/alongside the positive carbon atom of CH CH + ) [7] M. (a) Ag or silver or silver-based or silver on an alumina base epoxyethane (penalise specific silver compounds) Page 7 of 9

18 (b) electrophilic addition M: curly arrow from C=C bond towards/alongside the side of H atom on H-OSO OH (penalise M if arrow to H SO OR to formal charge on H of H-O bond) (ignore partial charges on H and O of H SO, but penalise if these are incorrect on the H atom being attacked) (credit M and M if correct curly arrow to H+ provided the anion is present) M: curly arrow from H O bond towards/alongside the side of the O atom on H OSO OH (credit the arrow even if there are partial or formal charges on H and O but the structure of H SO is correct) M: correct structure of the carbocation (penalise use of sticks in this structure) M: curly arrow from lone pair on an individual oxygen atom of (correct formula for) hydrogensulphate ion towards/alongside C atom bearing the positive charge (insist that the an ion has the correct formula with a lone pair of electrons and a negative charge) (c) (i) ethanal correct structure for ethanal (aldehyde functional group must be drawn out) (ii) oxidation or redox [0] M. (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 ) Page 8 of 9

19 H C=CH + H O CH CH OH (ignore state symbols) (credit use of C H 5 OH for ethanol) (penalise use of C H 6 O for ethanol on the first occasion) (credit C H and CH =CH for ethene) (penalise CH CH, CH.CH, CH :CH for ethene on the first occasion) (ignore H SO OR extra H O OR H + if it appears on both sides) conc. H SO OR conc. H PO (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 ) (ii) CH CH OH + O C + H O OR CH CH OH + ½O C + CO + H O (credit multiples of these equations) (credit use of C H 5 OH for ethanol) (penalise use of C H 6 O for ethanol, but note a possible repeat error from part (a) above) [5] M5. (a) Contains a C=C OR a double bond Page 9 of 9

20 (b) Electrophilic addition Mechanism: Both words needed Ignore partial negative charge on the double bond. M Penalise partial charges on bromine if wrong way and penalise formal charges Penalise once only in any part of the mechanism for a line and two dots to show a bond. M M M M Must show an arrow from the double bond towards one of the Br atoms on a Br-Br molecule. Deduct mark for sticks. Must show the breaking of the Br-Br bond. Is for the structure of the secondary carbocation with Br substituent. Must show an arrow from the lone pair of electrons on a negatively charged bromide ion towards the positively charged carbon atom. Deduct mark for wrong reactant, but mark consequentially. If HBr, mark the mechanism consequentially and deduct one mark If but--ene, mark the mechanism consequentially and deduct one mark. If both HBr and but--ene, mark the mechanism consequentially and deduct ONLY one mark. (c) (i) M Compounds with the same structural formula Penalise M if same structure Ignore references to same molecular formula or same empirical formula M With atoms/bonds/groups arranged differently in space OR atoms/bonds/groups have different spatial arrangements/ different orientation. Mark independently. Page 0 of 9

21 (ii) Award credit provided it is obvious that the candidate is drawing the trans isomer. Do not penalise poor C C bonds Trigonal planar structure not essential [9] M6. (a) (i) -bromo--methylpentane ONLY Must be correct spelling but ignore hyphens and commas (ii) Electrophilic addition (reaction) Both words needed Accept phonetic spelling (iii) M Displayed formula of -bromo--methylpentane All the bonds must be drawn out but ignore bond angles M Position(al) (isomerism) Do not forget to award this mark (iv) Structure of (E)--methylpent--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 C H 5 for ethyl Be 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 Page of 9

22 (b) (i) M R is represented by Spectrum M Spectrum shows an infrared absorption/spike/dip/ trough/peak with any value(s)/range within the range 60 to 680 (cm ) OR this range quoted/identified and this is due to C=C OR this information could be a correctly labelled absorption on the spectrum OR Spectrum does not have an infrared absorption in range 60 to 680 (cm ) and does not contain C=C. Award M if it is obvious that they are referring to the second spectrum (or the bottom one) M depends on a correct M Ignore other correctly labelled peaks Ignore reference to double bond or alkene (ii) Functional group (isomerism) (iii) Cyclohexane OR Methylcyclopentane etc. Named correctly Ignore structures and ignore numbers on the methyl group of methylcyclopentane [9] M7. (a) (i) (Free-) radical substitution Both words needed (ii) UV light/ultra-violet light/sunlight OR high temperature/50 C T 500 C (iii) Propagation (Step) Ignore first or second Accept phonetic spelling Page of 9

23 (iv) M Termination (Step) M CH CH CH C 6 H In M C 6 H may be drawn out as CH CH CH CH CH CH The dot may be anywhere around the terminal CH on the radical Accept C H 7 with dot anywhere Penalise the absence of any radical dot (v) C H 8 + 8Br C Br 8 + 8HBr Or multiples (b) (i) M Double bonds are electron-rich OR OR M OR OR electron pair donors centres of electron density. Bromine becomes polarised/becomes polar forms an induced dipole becomes δ+/δ M QoL require one of these terms Ignore (very) negative and nucleophile as applied to the double bond. Penalise M for ion formation from bromine For M, do not credit dipole formation solely as a consequence of electronegativity (ii) Electrophilic addition Both words needed Accept phonetic spelling (iii) Structure for,,,5-tetrabromopentane, for example BrCH CHBrCH CHBrCH Br OR Must be clear that they have drawn,,,5-tetrabromopentane and does NOT need to be displayed Credit use of sticks for each C-H bond Page of 9

24 (c) + M Structure of CH CHCH M (Secondary) Carbocation OR (secondary) carbonium ions Mark independently For M the positive charge must be on the central carbon atom Penalise bond to positive charge Penalise answers which show more than the correct carbocation e.g. the mechanism, unless the intermediate is clearly identified Credit use of sticks for each C-H bond For M, penalise primary or tertiary [] M8. (a) Position(al) (isomerism) (b) Penalise one mark from their total if half-headed arrows are used M must show an arrow from the double bond towards the H atom of the H Br molecule M Ignore partial negative charge on the double bond. M must show the breaking of the H Br bond. M Penalise partial charges on H Br bond if wrong way and penalise formal charges M is for the structure of the secondary carbocation. Penalise M if there is a bond drawn to the positive charge M 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 bond Maximum any of marks for wrong reactant or primary carbocation. If Br is used, maximum marks for their mechanism Do not penalise the use of sticks NB The arrows here are double-headed Page of 9

25 (c) Penalise one mark from their total if half-headed arrows are used M must show an arrow from the lone pair on oxygen of a negatively charged hydroxide ion to a correct H atom Penalise M if covalent KOH M 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 M) M is independent provided it is from their original molecule. Penalise M for formal charge on C of the C Br or incorrect partial charges on C Br Penalise M if an extra 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. Maximum any of marks for wrong reactant or wrong product (if shown) or a mechanism that leads to but--ene Accept the correct use of sticks for the molecule except for the C H being attacked Award full marks for an E mechanism in which M is on the correct carbocation. NB The arrows here are double-headed [8] M9. (a) (i) Penalise one mark from their total if half-headed arrows are used Penalise M for formal charge on C of the C-Br or incorrect partial charges on C-Br Ignore other partial charges Page 5 of 9

26 M 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. M 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 H bond in M M is independent but CE=0 if nucleophilic substitution N.B these are double-headed arrows (ii) Award mark if both correct stereoisomers but in the wrong places Accept no other alkenes. Be reasonably lenient on the bonds to ethyl (or to CH CH ) since the question is about E and Z positions but penalise once only if connection is clearly to the CH of CH CH Accept linear structures (iii) M (Compounds / molecules with) the same structural formula Penalise M if same structure M OR with atoms/bonds/groups arranged differently in space Ignore references to same molecular formula or same empirical formula or any reference to displayed formula atoms/bonds/groups that have different spatial arrangements / different orientation. Mark independently Page 6 of 9

27 (b) Mmust 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 H SO M could be to an H+ ion and M an independent O H bond break on a compound with molecular formula for H SO M Ignore partial negative charge on the double bond. M must show the breaking of the O H bond. M Penalise partial charges on O H bond if wrong way and penalise formal charges In M do not penalise incorrect structures for H SO M is for the structure of the carbocation. M 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. M NOT HSO For M, credit as shown or : OSO H ONLY with the negative charge anywhere on this ion OR correctly drawn out with the negative charge placed correctly on oxygen Penalise once only in any part of the mechanism for a line and two dots to show a bond NB The arrows here are double-headed Max of any marks for wrong organic reactant or wrong organic product (if shown) Accept the correct use of sticks [] Page 7 of 9

28 M0. (a) M electrophilic addition For M, both words required Accept phonetic spelling For the mechanism M Ignore partial negative charge on the double bond M must show an arrow from the double bond towards the H atom of the H Br molecule M Penalise partial charges on H Br bond if wrong way and penalise formal charges M must show the breaking of the H Br bond 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 correct (positively charged) carbon atom Maximum any of marks for the mechanism for wrong (organic) reactant OR wrong organic product (if shown) OR primary carbocation Accept the correct use of sticks NB These are double-headed arrows 5 Page 8 of 9

29 (b) M Nucleophilic substitution For M, both words required Accept phonetic spelling For the mechanism Penalise M if NH is negatively charged M must show an arrow from the lone pair of electrons on the nitrogen atom of an ammonia molecule to the correct C atom Penalise M for formal charge on C of the C Br or incorrect partial charges on C Br Penalise M for an additional arrow from the Br to something else M must show the movement of a pair of electrons from the C Br bond to the Br atom. Mark M independently provided it is from their original molecule The second mole of ammonia is not essential for M5; therefore ignore any species here M 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 atom Maximum any of marks for the mechanism for wrong organic reactant OR wrong organic product if shown Award full marks for an S N mechanism in which M is the attack of the ammonia on the intermediate carbocation Accept the correct use of sticks NB These are double-headed arrows 5 (c) M (addition) polymerisation OR poly-addition Ignore additional Credit polyprop--ene and polypropylene M poly(propene) / polypropene Penalise condensation polymerisation Page 9 of 9

30 (d) Penalise M if covalent KOH M must show an arrow from the lone pair on the oxygen of a negatively charged hydroxide ion to a correct H atom Penalise M for formal charge on C of C Br or incorrect partial charges on C Br. M 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 M Ignore other partial charges Penalise once only in any part of the mechanism for a line and two dots to show a bond M is independent provided it is from their original molecule, but CE=0 if nucleophilic substitution Maximum any of marks for wrong organic reactant Award full marks for an E mechanism in which M is on the correct carbocation. Accept the correct use of sticks for the molecule except for the C H being attacked NB These are double-headed arrows [5] M. (a) (i) Structure of (Z)-but--enenitrile with or without either or both of the CH and the CN groups displayed Penalise C NC Do not penalise C H C Ignore bond angles. (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. Page 0 of 9

31 (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 CH or the CN Penalise C NC Penalise sticks. Ignore brackets. Penalise n (c) Feature Absorption / peak in the range 0 to 60 cm or specified value in this range or marked correctly on spectrum and (characteristic absorption / peak for) C N / CN group / nitrile / cyanide group Feature Allow the words dip OR spike OR trough OR low transmittance as alternatives for absorption. Allow a peak at 00 cm to 0 cm in this case. Absorption / peak in the range 60 to 680 cm or specified value in this range or marked correctly on spectrum and (characteristic absorption / peak for) C=C group / alkene / carbon-carbon double bond Ignore reference to other absorptions eg C-H Either order. [5] M. (a) Structure for -methylbut--ene H C=CHCH(CH ) Any correct structural representation. Credit sticks and require the double bond. (b) Structure for -methylpropan--ol (CH ) COH Any correct structural representation. Credit sticks. Page of 9

32 (c) Structure for propene H C=CHCH Any correct structural representation. Credit sticks and require the double bond. (d) Structure for -aminobutane CH CH CH(NH )CH Any correct structural representation. Credit sticks. [] M. (a) M concentrated sulfuric acid OR c(onc) H SO If no reagent or incorrect reagent in M, CE= 0 and no marks for M or M M (cream solid) turns orange OR orange / red / brown fumes / gas / vapour If dilute sulfuric acid OR aq (alone) CE=0 M (yellow solid) turns black OR purple fumes / gas / vapour OR correct reference to H S observation (eg bad egg smell) OR as an alternative If H SO / sulfuric acid given but not stated whether dilute or concentrated, penalise M and mark on for M and M If incorrect formula for the acid, penalise M but mark M and M M concentrated ammonia OR c(onc) NH If NH / ammonia / aq ammonia given, but not stated as concentrated OR if dilute ammonia given, penalise M but mark on for M and M Ignore partially and ignore clear in M M (cream solid) dissolves / solution formed M precipitate remains / does not dissolve / insoluble OR no reaction / no change / (yellow solid) turns to white solid If incorrect formula for ammonia, penalise M but mark M and M In M for ammonia. ignore nothing (happens). ignore no observation. Page of 9

33 (b) M AgNO OR silver nitrate OR any soluble silver salt If no reagent OR incorrect reagent in M, CE= 0 and no marks for M OR M M white precipitate or white solid / white suspension An insoluble silver salt OR Tollens OR Ag OR ammoniacal silver nitrate or HCl / AgNO CE= 0 for the clip. M remains colourless OR no reaction OR no (observed) change OR no precipitate For M Credit acidified (OR HNO ) silver nitrate for M and mark on. If silver ions or incorrect formula for silver nitrate, penalise M but mark M and M Credit alternative test for nitrate ions For M Ignore cloudy solution OR suspension. For M Ignore nothing (happens). Ignore no observation. Ignore clear. Ignore dissolves. Page of 9

34 (c) M Br OR bromine (water) OR bromine (in CCl / organic solvent) If no reagent or incorrect reagent in M, CE= 0 and no marks for M or M Either Order M (stays) Orange / red / yellow / brown / the same OR no reaction OR no (observed) change OR reference to colour going to cyclohexane layer No credit for combustion observations; CE=0 For M in every case. Ignore nothing (happens). Ignore no observation. Ignore clear. M decolourised / goes colourless / loses its colour With bromine (water) For M, it must be a whole reagent and / or correct formula. If oxidation state given in name, it must be correct. For M penalise incorrect formula, but mark M and M OR as an alternative Use KMnO /H SO M acidified potassium manganate(vii) or KMnO /H SO OR KMnO / H + OR acidified KMnO M (stays) purple or no reaction or no (observed) change With potassium manganate(vii) For M M purple to colourless solution OR goes colourless If manganate or manganate(iv) or incorrect formula or no acid, penalise M but mark M and M Credit alternative test using iodine (for M) M (brown) to purple or accept no change, M colourless Credit alternative test using concentrated H SO M no change, M brown Credit alkaline / neutral KMnO for possible full marks but M gives brown precipitate or solution goes green. Page of 9

35 (d) M Tollens (reagent) OR ammoniacal silver nitrate OR a description of making Tollens (Ignore either AgNO or [Ag(NH ) + ] or the silver mirror test on their own, but mark M and M) M silver mirror OR black solid / precipitate (Ignore silver precipitate) M (stays) colourless or no reaction or no (observed) change If no reagent or incorrect reagent in M, CE= 0 and no marks for M or M For M in every case Ignore nothing (happens). Ignore no observation. Alternative using Fehling s (solution) M Fehling s (solution) or Benedict s solution (Ignore Cu + (aq) or CuSO on their own, but mark M and M) M Red solid / precipitate (Credit Orange or brown solid) M (stays) blue or no reaction or no (observed) change With potassium dichromate(vi) For M If dichromate or (potassium) dichromate(iv) or incorrect formula or no acid, penalise M but mark M and M Alternative using K Cr O 7 /H SO M acidified potassium dichromate or K Cr O 7 /H SO OR K Cr O 7 /H + OR acidified K Cr O 7 M (Orange to) green solution OR goes green M (stays) Orange or no reaction or no (observed) change For M Ignore dichromate described as yellow or red. With potassium manganate(vii) For M If manganate or (potassium manganate(iv) or incorrect formula or no acid, penalise M but mark M and M Alternative using KMnO /H SO M acidified potassium manganate(vii) or KMnO /H SO OR KMnO /H + OR acidified KMnO M purple to colourless solution OR goes colourless M (stays) purple or no reaction or no (observed) change Credit alkaline / neutral KMnO for possible full marks but M gives brown precipitate or solution goes green. [] Page 5 of 9

36 M. (a) (i) M (Yield) increases / goes up / gets more If M is blank, mark on and seek to credit the correct information in the explanation. If M is incorrect CE=0 for the clip. M The (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 heat M depends on a correct statement for M M depends on correct M and must refer to temperature / heat The (position of ) equilibrium shifts / moves left to right to oppose the decrease in temperature For M, the equilibrium shifts / moves to release heat OR to raise the temperature OR to heat up the reaction. (ii) M Concentration(s) (of reactants and products) remain or stay constant / the same For M credit [ ] for concentration. M Forward rate = reverse / backward rate Not 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. (b) KBr + H SO KHSO + HBr Credit this equation in its ionic form. Ignore state symbols. Credit multiples. Page 6 of 9

37 (c) M SO identified M correctly balanced equation (would also gain M) Credit M equation in its ionic form. Ignore state symbols. HBr + H SO Br + SO + H O Credit multiples. Not H SO on the right-hand side. Mark M independently M Oxidising agent OR electron acceptor OR oxidant OR to oxidise the bromide (ion) / HBr M Not electron pair acceptor. Page 7 of 9

38 (d) (i) M Electrophilic addition M both words required. For the mechanism M Penalise incorrect partial charges on O H bond and penalise formal charges Ignore partial negative charge on the double bond. M5 Not HSO For M5, credit as shown or : OSO H ONLY with the negative charge anywhere on this ion OR correctly drawn out with the negative charge placed correctly on oxygen. M 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 H SO M could be to an H + ion and M an independent O H bond break on a compound with molecular formula for H SO Max any of marks for a correct mechanism using the wrong organic reactant or wrong organic product (if shown) or a primary carbocation. M must show the breaking of the O H bond on H SO 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 M NB The arrows here are double-headed 5 (ii) Hydrolysis Credit (nucleophilic) substitution but do not accept any other prefix. Credit phonetic spelling. (iii) Catalyst [6] Page 8 of 9

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