chemistry higher level paper 3 - ib documents past papers - subject...(c) the graph below shows how...

8809-6103 33 pages

N09/4/CHEMI/HP3/ENG/TZ0/XX+

Wednesday 4 November 2009 (morning)

CHEMISTRYHIgHER lEvElPaPER 3

INSTRUCTIONS TO CANDIDATES

• Write your session number in the boxes above.• Do not open this examination paper until instructed to do so.• Answer all of the questions from two of the Options in the spaces provided. You may continue

your answers on answer sheets. Write your session number on each answer sheet, and attach them to this examination paper and your cover sheet using the tag provided.

• At the end of the examination, indicate the letters of the Options answered in the candidate box on your cover sheet and indicate the number of answer sheets used in the appropriate box on your cover sheet.

1 hour 15 minutes

Candidate session number

8 8 0 9 6 1 0 3

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Option A — Modern analytical chemistry

A1. 1HNMRandIRspectroscopybothinvolvetheabsorptionofelectromagneticradiation.

(a) (i) Identifytheregionoftheelectromagneticspectrumusedin1HNMRspectroscopy.

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(ii) Explain why tetramethylsilane (TMS) is used as a reference standard in1HNMRspectroscopy.

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(b) IdentifywhichofthefollowingmoleculesabsorbsIRradiationandexplainyourchoice.

H2 O2 HCl

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A2. (a) The mass spectrum of an unknown compound, X, of empirical formula C2H4O isshownbelow.

Intensity%

20 40 60 80 100Mass/charge

[Source:CleapssGuides:L202Spectra(CleapssSchoolScienceService),Sept2000.]

(i) DeterminetherelativemolecularmassofXfromthemassspectrumanddeducetheformulaofthemolecularion.

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(ii) Identifyafragmentwhichgivesrisetothepeakatm/z =29.

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(iii) Commentontheabsenceofapeakatm/z =59.

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(This question continues on the following page)

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(Question A2 continued)

(b) TheIRspectrumofXisshownbelow.%Transmittance

04000 3000 2000 1500 1000 500

Wavenumber/cm–1

[Source:http://modbo1.ibase.go.jp/sdbs/cgi-bin/cre_index.cgi?lang=eng]

(i) UseTable17of theDataBooklet to identify thebondswhichcorrespondto theabsorptionsAandB.

A: .............................................................

B: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) DeducethenameofthefunctionalgrouppresentinX.

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(c) Typical proton chemical shift values are given in Table 18 of the Data Booklet.The1HNMRspectrumofXcontainsthreepeaks.Detailsoftwooftheseareshowninthetablebelow.

Peak Chemical shift / ppm Relative peak area Splitting pattern

First 2.0 3 Singlet

Second 4.1 2 Quartet

(i) Deduce a possible structure for X that is consistent with the mass, IR and1HNMRspectra. [1]

(ii) Complete the table above by suggesting the chemical shift of the third peak,andstateitsrelativepeakareaandsplittingpattern. [3]

(iii) Explainthesplittingpatternofthepeakatchemicalshift4.1 ppm.

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A3. Chromatographyisusedtotestforthepresenceofillegaldrugsinsport.

(a) AchromatogramofaconcentratedurinesamplefromanathleteshowsthepresenceofabannedsubstanceknowntohaveanRfvalueof0.75.

(i) CalculatetheRfvaluesforAandB,andsodeducewhichofthespotscorrespondstothebannedsubstance. [2]

solventfront

Rfof A:

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Rf ofB:

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Bannedsubstance:

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(ii) Suggest how the results could change if the experiment was repeated with adifferentsolvent.

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(b) Paperandcolumnchromatographybothhavestationaryandmobilephases.Identifythestationaryphasesinthedifferenttechniques.

Paperchromatography:

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Columnchromatography:

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A4. Thecomplexion[Ni(H2O)6]2+isgreenand[Ni(NH3)6]

2+isblue.Explainwhythe[Ni(H2O)6]2+

complexioniscolouredandoutlinewhychangingtheidentityoftheligandchangesthecolouroftheion.

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Option B — Human biochemistry

B1. Proteinsarevitalcomponentsoflivingsystems.

(a) Statethegeneralformulaof2-aminoacids.

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(b) State two characteristicpropertiesof2-aminoacids.

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(c) UsingTable 19 of theDataBooklet, deduce the structural formula of two dipeptidesthatcouldbeformedbythereactionofalaninewithserineandstatetheotherproductofthereaction.

Otherproductofthereaction:

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(d) Explainthedifferencebetweentheprimaryandsecondarystructureofproteins.

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(Question B1 continued)

(e) Explainhowasampleofaproteincanbeanalysedbyelectrophoresis.

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B2. Enzymesareproteinswhichplayanimportantroleinthebiochemicalprocessesoccurringinthebody.

(a) Statethemajorfunctionofenzymesinthehumanbody.

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(b) Describethemechanismofenzymeactionintermsofstructure.

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(c) Thegraphbelowshowshow the rateof anenzyme-catalysed reactionchangesas thesubstrateconcentrationisincreased.

(i) UsethegraphtodetermineVmaxandtheMichaelisconstant,Km. [2]

Rate/10–6molmin

00 5 10 15 20 25

[S]/10–3moldm–3

Vmax: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Km: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Drawalineonthegraphtorepresenttheeffectofaddingacompetitiveinhibitor. [1]

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(Question B2 continued)

(d) State and explain the effects of heavy-metal ions and temperature increases onenzymeactivity.

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Option C — Chemistry in industry and technology

C1. (a) Aluminiumisextractedbytheelectrolysisofamoltenmixturecontainingalumina,Al2O3,usinggraphiteelectrodes.

(i) Stateahalf-equationforthereactionatthenegativeelectrode(cathode).

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(ii) Oxygenisproducedatthepositiveelectrode(anode).Statethenameofanothergasproducedatthiselectrode.

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(b) (i) State two properties of aluminium thatmake it suitable for use as an overheadelectriccable.

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(ii) Alloysofaluminiumwithnickelareusedtomakeengineparts.Explain,byreferringtothestructureofthesealloys,whytheyarelessmalleablethanpurealuminium.

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C2. Polyvinylchloride(PVC)andpolyethenearebothpolymersmadefromcrudeoil.

(a) ExplainwhyPVCislessflexiblethanpolyethene.

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(b) StatehowPVCcanbemademoreflexibleduringitsmanufactureandexplaintheincreaseinflexibilityonamolecularlevel.

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(c) PVCcanexist in isotacticandatacticforms. Drawthestructureof the isotacticformshowingachainofatleastsixcarbonatoms. [1]

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C3. Nano-sized‘test-tubes’withoneopenend,canbeformedfromcarbonstructures.

(a) Describethese‘test-tubes’withreferencetothestructuresofcarbonallotropes.

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(b) Carbonnanotubescanbeusedascatalysts.

(i) Suggesttworeasonswhytheyareeffectiveheterogeneouscatalysts.

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(ii) Stateonepotentialconcernassociatedwiththeuseofcarbonnanotubes.

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C4. Rechargeable nickel-cadmium batteries are used in portable electrical equipment andemergencylighting.

Thedischargeprocesscanbesummarizedbytheequationbelow.

2 2 22 2 2NiO OH s Cd s H O l Ni OH s Cd OH s( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )+ + +

(a) Statethechangeinoxidationnumberofthecadmiumanddeduceif it isactingasthepositiveornegativeelectrodeduringthedischargeprocess.

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(b) IdentifyaphysicalpropertyofCd(OH)2whichallowsthisprocesstobereversedandthebatteryrecharged.

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C5. The structure of 4-pentyl-4-cyanobiphenyl, a commercially available nematic crystallinematerialusedinelectricaldisplaydevices,isshownbelow.

CNC5H11

(a) Explainhowthethreedifferentpartsofthemoleculecontributetothepropertiesofthecompoundusedinelectricaldisplaydevices.

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......................................................................

C5H11:

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(b) Describeandexplaininmoleculartermstheworkingsofatwistednematicliquidcrystal.

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Option D — Medicines and drugs

D1. Thediscoveryofpenicillinwasoneofthemostsignificantscientificdiscoveriesofthelastcentury.

(a) Describethemodeofactionofpenicillinsintreatinginfectiousdiseases.

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(b) Ampicillinisasemi-syntheticpenicillinusedtotreatlunginfections.Thestructureoftheantibioticisshownbelow.

NH2CH3

(i) Explainwhyitisimportanttocontinuetodevelopsemi-syntheticpenicillins.

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(ii) Describehowcomputersareusedindrugdesign.

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(Question D1 continued)

(c) Statethetypeofhybridizationofeachofthecarbonatoms(I,II,andIII)intheβ-lactamringofampicillinbycompleting the tablebelow,andexplainwhytheamidegroup ishighlyreactive. [2]

Carbon atom I II III

Hybridization

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D2. (a) Explainthemeaningoftheterms:

(i) side-effect

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(ii) therapeutic window

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(iii) placebo effect.

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(b) Theeffectivenessofadrugdependsonthemethodofadministration.

(i) Onemethod of injecting drugs into the body results in the drug having a veryrapideffect.Statethemethodandexplainitsrapidaction.

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(ii) Listthetwoothermethodswhichcanbeusedtoinjectdrugsintothebody.

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(iii) Identify the method of administration used to treat respiratory diseases suchasasthma.

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D3. Amphetamineandmethamphetaminearewidelyabuseddrugs.

(a) Stateoneshort-termeffectofamphetamineonthehumanbody.

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(b) Explainwhy amphetamine is classified as a sympathomimetic drug and relate this toitsstructure.

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(c) Regularuseofamphetamineandmethamphetaminecanleadto tolerance.Explainwhythisispotentiallydangerous.

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(d) Amphetamine exists as optical isomers. Describe how chiral auxiliaries can beused to synthesize only the desired enantiomeric form of a drug from a non-chiralstartingcompound.

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(e) The structures of morphine and heroin are shown in Table 20 of the Data Booklet.Explaintheincreasedpotencyofheroincomparedtomorphine.

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Option E — Environmental chemistry

E1. It is now widely accepted that the increased production of carbon dioxide is leading toglobalwarming.

(a) Describehowcarbondioxideactsasagreenhousegas.

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(b) Discusstheinfluenceofincreasingamountsofgreenhousegasesontheenvironment.

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E2. Thebiochemicaloxygendemand(BOD)isameasureofwaterpollution.

(a) Identify the stage of sewage treatmentwhich removes the substances responsible forhighBODvaluesandexplainhowthisisdone.

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(b) DescribehowtheadditionofnitratesorphosphatestowatercanincreasetheBODvalueofawatersample.

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E3. Theconcentrationofsomepollutantsinacitywasmeasuredovera24hourperiod.Theresultsareshownbelow.

Concentration

Hydrocarbons

5 6 7 8 9 10 11 Noon 1 2 3 4 5 6 7 8 9 10 11 Mid- 1 2 3 4Sunrise am pm Sunset night

Timeofday

(a) OutlinethecauseoftheincreaseinNOlevelsbetween5and8am.

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(b) Outlinethecauseoftheincreaseinconcentrationofperoxyacylnitrates(PANs)between8amand2pm.

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(c) Statewhyatemperatureinversionoftenresultsintheformationofsmog.

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(d) Show,bystatinganequation,howoneoftheabovepollutantsreactswithHOradicalstoproduceaconstituentofacidrain.

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E4. Landfillsitesareusedtodisposeofabout90%oftheworld’sdomesticwaste,butincinerationisbeingincreasinglyusedinsomecountries.

(a) State one advantageofeachmethod.

Landfill:

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Incineration:

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(b) Suggestwhysomebiodegradableplasticsdonotdecomposeinlandfillsites.

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(c) High-level and low-level wastes are two types of radioactive waste. Compare thehalf-livesandthemethodsofdisposalofthetwotypesofwaste.

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E5. Compoundsofheavymetalsareonetypeoftoxicsubstancefoundinwater.Lead(II)ions,Pb2+,can be removed by bubbling hydrogen sulfide,H2S, through pollutedwater. The solubilityproductofleadsulfideis1 25 10 2528 2 6. × − − °mol dm at C.

(a) CalculatetheconcentrationofPb2+ionsinasaturatedsolutionofleadsulfide.

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(b) ExplainhowtheadditionofhydrogensulfidedecreasestheconcentrationofPb2+ionsinasaturatedsolution.

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Option F — Food chemistry

F1. Malnutrition can be caused by starvation, dieting or a person eating an excess of highlyprocessedfood.

(a) Stateonefunctionofanutrient.

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(b) Describethestructuralcompositionofthefollowingnutrients:

(i) fatsandoils

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(ii) monosaccharides.

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(c) Liver is a source of arachidonic acid, CH3(CH2)4(CH=CHCH2)4(CH2)2COOH, andfishoilsareasourceoflinolenicacid.WithreferencetothestructureoflinolenicacidinTable22oftheDataBooklet,explainwhyarachidonicacidhasamuchlowermeltingpointcomparedtolinolenicacid,eventhoughitcontainstwomorecarbonatoms.

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F2. Antioxidantscanbeusedtoprolongtheshelflifeoffood.

(a) Definetheterms:

(i) shelf life

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(ii) antioxidant.

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(b) UsingTable 22 of theData Booklet, and the structure of propyl gallate (PG) below,comparethestructuralfeaturesofthethreecommonantioxidants3-BHA,BHTandPG.

COOCH2CH2CH3

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(Question F2 continued)

(c) Stateoneexampleofacommonnaturallyoccurringantioxidantandstateonepossiblelong-termhealthbenefitofconsumingfoodinwhichitispresent.

Antioxidant:

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Long-termhealthbenefit:

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(d) (EDTA)4–,theethylenediaminetetraacetateanion,isachelateligandwiththefollowingstructure.

CH2 CH2

CH2CH2

IthasbeenfoundtoinhibittheFe2+catalysedoxidationofrawbeef.Explainwhy(EDTA)4–canbedescribedasachelateligand.

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F3. Differentconventionsareusedtoclassifyenantiomers.Orangeandlemonpeeleachcontaindifferent enantiomers of the compound limonene. One of the enantiomers is representedbelow.

(a) Identifythechiralcentreinthisenantiomerwithanasterisk,*. [1]

(b) The(+)d-enantiomerhasthecharacteristicsmelloforangesandthe(–)l-enantiomerhasthecharacteristicsmellof lemons. Explain themeaningof the (+)dand (–)l symbolsusedinthisnotation.

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(c) TheR,Snotationisalsoused.The(+)d-enantiomerisoftendescribedasR-limoneneandthe(–)l-enantiomerasS-limonene.ExplainwhatismeantbytheR,SnotationandstatewhetherthestructureshownisRorS.

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F4. The chemical process that makes butter rancid is called oxidative rancidity. Describe,using equations, the steps involved in the free-radical chainmechanism that occurs duringoxidativerancidity.

Initiation:

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Propagation:

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Termination:

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Option G — Further organic chemistry

G1. Thecarbonylchemistryofbothaldehydesandketones involvesanumberofdifferent typesofreactions.

(a) Statetheformulasoftheproducts,A–C,formedinthefollowingreactions.

(i) CH3CH2MgBr(CH3)2CO → A+B

A: .............................................................

B: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CH3CHO + NHH2N C + H2O→

C: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) StatethetypeofreactioninvolvedintheformationofCandH2Oin(a)(ii).

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G2. Ethanoicacidandchloroethanoicacidbothcontainthecarboxylgroup.

(a) Explainwhychloroethanoicacidisastrongeracidthanethanoicacid.

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(b) Starting with chloromethane, outline one possible reaction pathway to synthesizeethanoicacid.Youranswershouldinclude: thereagentsused arelevantchemicalequationforeachstep.

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G3. (a) Alkenescommonlyreactbyelectrophilicadditionreactions.Describethemechanismofthefollowingreaction,usingcurlyarrowstoshowthemovementofelectronpairs,andsuggestthereasonfortheformationofthemajororganicproduct,D.

CH2=CH(CH2CH3)+ →HI D

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(Question G3 continued)

(b) Both benzene and methylbenzene undergo electrophilic substitution reactions.Statetheformulasofthereagents,E–G,including any catalysts used,inthefollowingconversions.

E: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CH3 CH3

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G : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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(Question G3 continued)

(c) StatetheformulasoftheproductsHandI,formedinthefollowingreaction.

C H CH Br NaOH6 5 2 + → H +I

H: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(d) (i) Statewhether–OHcanbedescribedasanactivatingordeactivatinggroupwithrespecttoaromaticelectrophilicsubstitutionreactions.

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(ii) Describethedirectingeffectof–OHonabenzeneringinanaromaticelectrophilicsubstitutionreaction.

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(iii) Explain the decreased reactivity due to the presence of the –NO2 group in anaromaticelectrophilicsubstitutionreaction.

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(e) Considerthetwoaminesmethylamine,CH3NH2,anddimethylamine,(CH3)2NH.

(i) UsingTable15oftheDataBooklet,statewhichoftheaminesisthemorebasic.

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(ii) Explaintherelativebasicitiesofthetwoamines.

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3 3 3 3

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