Name: Student Code:34th International Chemistry OlympiadGroningen, Wednesday, 10 July 2002Theoretical !aminationChemistry and the Quality of Life go Hand in HandTheme I Chemistry o" #i"eI$1 O!ygen in %our #i"eI$2 &itrogen Cycle in &atureTheme II Chemistry o" Industrial 'ele(anceII$1 Inulin, a &e) 'ene)a*le 'a) +aterialII$2 ,roduction o" +ethanolII$3 -ramids, .igh$,er"ormance ,olymeric +aterialsTheme III Chemistry o" /unctional +olecules in &atureIII$1 ,hospholipids in +em*ranesIII$2 Glutathione, an ssential +ini$,eptideTheme I0 Chemistry 'elated to #ight and nergyI0$1 #ighting #ampsI0$2 'ed 'u*yI0$3 0ehicle Traction 1atteriesOfficial Version IName: Student Code: Write your name and student code (posted at your station) on all the pages of the theoreticalexamination. You have 5 hours to complete all the tasks and record your results in the answer oxes! you muststopyour workimmediatelyafterthe"#O$ commandisgiven.% delayindoingthisy&minutes will lead to cancellation of the current task and will result in 'ero points for the task. %ll results must e written in the appropriate oxes on the pages. %nything written elsewherewill not emarked. (onot writeanythingontheackofyour answersheets. )fyouneedadditional sheets or a replacement sheet! re*uest it from the supervisor. +or a sanitary stop, ask your supervisor for permission. When you have finished the examination!youmustput allofyour papersintotheenvelopeprovided! then you must seal the envelope. Only papers in the sealed envelope will e marked. % receipt will e issued for your sealed envelope. (o not leave the examination room until youare directed to do so. -se only the pen and calculator provided. % copy of the $eriodic #ale of the .lements is provided. #his examination paper has &/ pages of prolems including answer oxes. %n official .nglish0language version is availale only on re*uest.Official Version IIName: Student Code:Theme 1 - Chemistry of LifeLiferunsonchemistry.Understandingandmonitoringlifeprocessesreceivemuchattention in chemistry.Problem I-1 Oxygen in Your Life Sore:! "ointsOxygen is of vital importance for all of us. Oxygen enters the ody via the lungs and is transported tothe tissues in our ody y lood. #here it can deliver energy y the oxidation of sugars,123/4O252 O42 1O452 34O#his reaction releases 677 k8 of energy per mol of oxygen. O4 uptake y lood is at four heme (3m)groups in the protein hemogloin (3). +ree 3m consists of an +e45 ion attached to four 9 atoms of a porphyrin40 ligand. Oxygen can ind atthe coordination site of +e45 giving a 3m#O4 complex. 1aron monoxide can e complexed similarly!givinga3m#1Ocomplex.1Ois apoisonas it inds morestronglyto3mthanO4does. #hee*uilirium constant K/ for the reaction,3m 5 1O 3m#1O (/)is /7777 times larger than the e*uilirium constant K4 for the reaction,3m 5 O43m#O4(4).ach 3 molecule can take up four molecules of O4. :lood in contact with O4asors a fraction ofthis amount! depending on the oxygen pressure! as shown in +igure / (curve /). %lso shown are thecurves(4)and(&)forloodwithtwokindsofdeficient 3. #heseoccurinpatientswithcertainhereditary diseases.7 /7 477/oxygenated fraction of hemogloinoxygen pressure! k$a(4)(/)(&)+igure /Official Version/ 4 & 6 5;arks $% $% 1% $% 1&/5 5Oxygen pressure! k$aOxygenated fraction of hemoglo

in1Name: Student Code: /706m&s0/. #he red cells in lood occupy 67? of the lood volume=inside the cells the concentration of 3 is &67 kg m0&= 3 has a molar mass of 26 kg mol0/. R @ A.&/6 8mol0/ B0/.T @ 4CA B.I-1-1 -sing the relation etween K and the standard Dis energy G7 for a reaction! calculate thedifference etween the G7 values for the heme reactions (/) and (4).%nswer, 1alculation,I-1-$ .stimatefrom+igure/(to4significant figures)howmanymolesofO4aredepositedinmuscle tissue when one mole of 3 travels from the lungs to the muscles and ack again forthe three different types of 3.3 type /, 3 type 4, 3 type &, I-1-' #hespecial "0shapeduptakecurve/istheresult ofsutlestructural featuresof3. #hedeficient 3 shown in curve 4 is not optimal ecause, #he inding with O4 is too weak. #he inding with O4 is too strong. #he maximum oxygen capacity is too low. #he deficiency is caused y caron monoxide poisoning.Official Version $Name: Student Code:Official Version 'Name: Student Code:I-1-( 1alculate how much oxygen (in mol s0/) can e deposited in tissue y lood with normal 3(/).%nswer, 1alculation,I-1-% 1alculate the maximum powerthat the ody can produce (assuming it is limited y oxygentransfer).%nswer, 1alculation,Official Version (Name: Student Code:Problem I-$ Nitrogen Cyle in Nature Sore:) "oints%mmonia is a toxic sustance to marine animals at levels exceeding / ppm. 9itrifying acteria play animportant role in the conversion of 93& first to nitrite and then to nitrate! the storage form of nitrogenin the soil.Nitrosomonasbacteria93&54 O459%(39O4

54 34O59%(0 *9%(3 is the iochemical reducing agent of the coen'yme nicotinamide dinucleotide (9%()! 9%(5 isthe oxidi'ed form of the coen'yme 9%(.4 9O& -Nitrobacterbacteria4 9O45O4-I-$-1 Dive the oxidation states of 9 in the following series,(-se the oxes elow the compounds)93&9O49O&0 0#he spectrophotometric analysis of nitrite is ased on a reaction with an indicator. #he coloured product then otained has an asorance maximum at @ 56& nm.+or *uantitative analyses a caliration curve has to e made! in which asorance at the maximum asorance wavelength @ 56& nm is plotted against nitrite concentration in a series of standards.I-$-$ #he measurements are performed at the wavelength with the maximal asorance ecause, #here is no interference of impurities #here is no contriution of stray light #here is optimal accuracy of the measurement 9one of these statements;ark the correct answer.Official Version/ 4 & 6 5;arks 1% 1% $& $% $%%Name: Student Code:#he asorption is measured with a single eam spectrophotometer. 3owever 5? of the light! the so0called stray light Is! strikes the detector directly (see +igure 4).I7IIsl+igure 4I-$-' 1alculate the value of the asorance A shown y the spectrophotometer if @ 2777 ;0/ cm0/! l @ / cm and c @ / > /706 ;%nswer,1alculation,+or a nitrite determination in water the following data have een measured.concentration of nitrite nitrogen (ppm) asorance at 56& nm (/.777 cm cuvet)lank 7.77& (due to impurities in the solvent)7.C/5 7./2E/.A&7 7.&4AOfficial Version !Name: Student Code:I-$-( (etermine from the data given aove! using the values corrected for the solvent impurities! theslope m and the intercept b of the caliration curve A @ m c 5 b.%nswer,1alculation of m ,1alculation of b ,F#he duplicate analyses of a water sample are given elow. #he measurements have een performed ata wavelength of 56& nm and in a 4.777 cm cuvet.water sample asoranceanalysis / 7.524analysis 4 7.556+or the calculation of the concentration of the nitrite nitrogen (c in ppm) the e*uation otained y themethod of least s*uarescorrected asorance @ 7./E2C c 5 7.77/5may e applied! using the measurements in a /.777 cm cuvet.I-$-% 1alculate the average nitrite nitrogen concentration in ppm and g mG0/. 3int, #ake the lank from prolem )0406.%nswer, 1alculation,Official Version )Name: Student Code:Theme II - Chemistry of Industrial +ele,aneInourdailylifeeusemanyproductsthat areproducedonanindustrial scale.!astering the underlying chemistry is at the heart of this business.Problem II-1 Inulin- a Ne. +ene.able +a. /aterial Sore:! "oints)nulin! which is produced from chicory roots in :elgium and#he 9etherlands! is used as a food additive as it has aeneficial effect on the intestinal flora. )t is also used as sourceoffructose whichis /.Ctimes sweeter thansucrose!andfortheproductionof mannitol whichisusedinchewinggum.)nulin is a linear polymer of fructose units with a glucose unitat one end= its 3aworth proHection formula is shown at the left.)n this prolem inulin has /7 fructose units (n @ C).II-1-1 )nulin may e hydroly'ed under 350catalysisconditions. Of the four options elow (0!1!C and 2) indicate which 10O ond cleavage ismost likely to occur.O 3OOO 31343O341O 3O 3OO513433O341O 3OOO 31343O341O 3O 3OO513433O341O 3OOO 31343O341O 3O 3OO1343O3413O 3OOO 31343O341O 3O 3O5 O1343O34130 1 C 25;ark the correct cleavage mechanism for the most efficient hydrolysis.Official Version/ 4 & 6 5;arks 1% 1% '& 1& '&O 3O3O 3OO1343O341O 3O134O3O3O3O 3OO134O33O341n3Name: Student Code:3ydrolysis with isotopically laelled water can provide information aout the mechanismofhydrolysis using modern 9;< techni*ues! which can IseeJ deuterium (43) and the oxygen isotope/EO.II-1-$ )ndicate which laelled water can best e used for this purpose. ;ark the correct answer.434O 34/EO434/EO 9one of them.-pon catalytic hydrogenation glucose gives soritol (S)! whilst fructose (4) gives mannitol (/) andsoritol (S).II-1-' (raw the +ischer proHections of fructose (4)! soritol (S) and mannitol (/).4S/5/.77;ole of inulinin 4.77kgof water with addedcatalysts! is suHectedto hydrolysis andhydrogenationat C5o1inaonestepprocess. #heselectivityofthehydrogenationoffructosetomannitol K soritol is E K &.II-1-( 3ow many moles of mannitol and soritol are otainedL/, S,Official Version 5Name: Student Code:%fter completion of the reactions the catalysts are removed and the reaction mixture is cooled to 45o1. #he soluility of / is 7.67 mol kg0/ in water at 45 o1 and the soluility of S is so high that it willnot precipitate.II-1-% 1alculate how many moles of / will precipitate.%nswer, 1alculation,Official Version 1&Name: Student Code:Problem II-$ Prodution of /ethanol Sore:! "oints;ethanol (13&O3) is a chemical that is used for the production of additives in gasoline and manycommon plastics. % factory! producing methanol! is ased on the reaction,1O54 3413&O33ydrogen and 1O are otained y the reaction,136534O 1O5& 34#he three units of the factory! namely! the IreformerJ for the hydrogen K caron monoxide production!theImethanol reactorJandaIseparatorJtoseparatemethanol from1Oand34!areschematicallyshown in +igure /. +our positions are indicated y ! ! and .reformermethanolreactorseparator13634O1O 3413&O31O34+igure /#he flow of methanol at position is n M13&O3! N @ /777 mol s0/. #he factory is so designed that 4K&of the 1O is converted to methanol. .xcess 1O and 34 at position are used to heat the first reactor.%ssume that the reformer reaction goes to completion.II-$-1 1alculate the flow of 1O and 34 at position .II-$-$ 1alculate the flow of 1O and 34 at position .II-$-' 1alculate the flows of 136 and 34O needed at position .Official Version/ 4 & 6 5;arks 1% $& 1% $% $%11Name: Student Code:II-$-( %t point all species are gases. 1alculate the partial pressures in ;$a for 1O! 34 and 13&O3 at position using the e*uation,pi @ pnintotwherein ni is the flow and pi the partial pressure of the compound i! ntot is the total flow at theposition considered! and p the total pressure in the system. (p @ /7 ;$a)%nswer p M1O! N, %nswer p M34! N, 1alculations,Whenthemethanol reactor islargeenoughthereactiongoestoe*uilirium. #hepartialpressures at point oey the e*uation,pCOp6$$pC6'O6Kp @ p&$wherein p7 is a constant (7./ ;$a) and Kp is a function of temperature as is shown in +igure 4 (the vertical scale is logarithmic)./706/70&/704/70//77Kp677 577 277 E77 T! BOfficial Version 1$Name: Student Code:+igure 4Official Version 1'Name: Student Code:II-$-% 1alculate Kp and indicate at which temperature T the reaction must e operated to achieve thise*uilirium.%nswer Kp, %nswer T, 1alculation,Official Version 1(Name: Student Code:Problem II-' 0ramids- 6igh-Performane Polymeri /aterialsSore:! "oints%romatic polyamides(aramids) are high strength! high performance polymer fiers that find use incomposite materials! ullet0proof vests! high *ualityskis! safetyhelmets! etc. %ramid $$#%ismarketed under the names BevlarO ((u$ont) and #waronO (#eiHin)! and amongst others manufacturedinthenorthof #he9etherlands.#he$$#% chainsareneatlypacked intofierswithasheet typestructure.9 93OO3$$#%nII-'-1 (raw the structure of these sheets (three chains suffice).Official Version/ 4 & 6;arks $& '& $% $%1%Name: Student Code:+or a polymerisation of e*uimolar amounts of two monomers the average chain length isn" ! thedegree of conversion is p! which e*uals the fraction of functional groups that have reacted! the totalnumer of chains is Nt and the total initial numer of monomers is U7.%ssuming that the polymeri'ation e*uilirium can fully e descried y,1 5 %%m 5 34OWhere1standsforanyP1O4group!% standsforanyP934groupand %mstandsforanyamidegroup.II-'-$ 1alculate the degree of conversion needed to otain an average chain length of 577.%nswer, 1alculation,II-'-' +or the synthesis of $$#% the following possiilities are considered. Which of the following reactions will workL ;ark the correct answer(s).3O41 1O43 9 34934O1l 1lO9 34934O O;eO O;e9 34934O1;e&;e&1OO O9 34934 (/47 Q1)polarsolventasepolarsolvent&7 Q1polarsolvent*$$#%*$$#%*$$#%*$$#%45 Q1diethyl etherOfficial Version 1!Name: Student Code:II-'-( %nother type of aramid can e produced from60aminoen'oic acid (60aminoen'ene0caroxylic acid) y heating.7a8 Dive the structure of this aramid (n @ 6)7b81alculatetheaveragechainlengthat e*uilirium(reactioniscarriedout ina closedvessel). #he e*uilirium constant K @ 5E2.%nswer,n"@ 1alculation,Official Version 1)Name: Student Code:Theme III - Chemistry of 4untional /oleules in NatureA challenge in chemistry is to discover hat nature does and ho the structures ofbiologically active molecules are related to hat they do.Problem III-1 Phos"holi"ids in /embranes Sore:! "oints:iological cell memranes are complex! functional! non0covalent molecular assemlies! largelyconsisting of lipids and proteins. #heir function is of vital importance for life processes. #hey separatethe cell from its environmentand also determine the specific flow of information etween the cellcontents andtheenvironment. $hospholipids areamongthemost important components of cellmemranes. %n example is compound 0.-pondispersioninwater (aovealowcritical concentration)compound0forms closedilayerstructures! called liposomes! which are employed as model compounds for aspects of the chemistry ofthestructurallymuchmorecomplexcell memranes. Giposomesaregloularaggregateswiththepolar or ionic head groups in contact with water and with the alkyl tails se*uestered in a hydrophoiccore. #he ilayer structure encloses an a*ueous inner compartment.(oule0tailed syntheticsurfactants also form closed ilayer assemlies similar to liposomes ut nowcalled vesicles. %n example is di0n0dodecyldimethylammonium chloride (220C).Official Version/ 4 & 6 5;arks $& $& $& $& $&1