DEPARTAMENTO DE
CIENCIAS NATURALES / Year 12 IB Chemistry
3rd Term test
Option D (60 minutes)
Name and surnames ______
Date ______Marks. A__/16 B__/14 C__ /10
  1. Pharmaceuticalproductscan oftenundergo up to 12 years of development and testingbeforebeingsoldcommercially. Define thefollowingterms in relation to thisprocess.
  2. LD50

Lethaldose to 50 % of animal population

(A1)

  1. Therapeuticwindow

Range of doses between ED50 and TD50 that a drug can safely be admitted

(A1)

  1. Bioavailability

The % of a drugthatreachesbloodstream; do notacceptamount

(A1)

  1. Aspirinisone of themostwidelyuseddrugsworldwide.
  1. Itisused as both a mildanalgesic (painkiller) and also as a prophylactic.
  1. Explainhow a mildanalgesicworks.

Preventsreleases of prostaglandins; no stimulation of painreceptors

(A2)

  1. Explainwhatismeantby “prophylactic” and giveoneexample of a physiologicaleffect in thiscontext.

A drugtaken as a preventativemeasure; anticoagulant

(B1)

  1. Aspirinisproducedvia a reactionbetweensalycilicacid and ethanoicanhydride as shownbelow.
  1. Excludingthebenzene ring, statethe 2 functionalgroupsfound in aspirin.

Carboxylicacid;ester

(A1)

  1. The final stage of thesynthesisispurification to removeimpuritiesfromthewhiteproductobtained.
  1. Statethename of thepurificationprocesscommonlyused.

Recrystallisation

(A1)

  1. Theliteraturevalueforthemeltingpoint of aspirinis 159 ºC. Ifthe experimental valuewasseen to be 151 ºC, calculatethe % error betweenthetwovalues.

5%

(C1)

  1. Theterm “dyspepsia” isused to describe feelings of pain and discomfort in theupper abdomen. These can includeheartburn, indigestion and ulceration. There are a variety of drugswhich can be used to treatdyspepsia.
  1. OnesuchexampleisRanitidine(Zantac).
  1. ExplainhowZantac reduces acidsecretion in thestomach.

Zantacinteractswith H2 receptors; preventshistamineinteractingwith H2 receptors; preventssecretion of acidintostomach (ANY 2)

(A2)

  1. Use the data booklet to state 1 functionalgroupsharedbybothZantac and histamine.

Amine (secondaryortertiary)

(A1)

  1. Antacids are a commontreatment and oftencontain metal carbonates such as Na2CO3.
  2. Write a balancedequationbetweensodium carbonate and hydrochloricacid.

Na2CO3 + 2HCl  2NaCl + H2O + CO2

(A1)

  1. Describe 1 problemassociatedwiththe use of carbonates and hydrogencarbonates as antacids.

Production of carbondioxide gas

(A1)

  1. Magnesiumhydroxide and aluminiumhydroxide can also be used as antacids. Show whichwouldneutralisethegreateramount of hydrochloricacidif 0.3 moles of each are used.

Mg(OH)2  2OH- so 0.6 produced; Al(OH)3  3 OH- so0.9 moles OH-

(C2)

  1. The Henderson-Hasselbachequationsfound in thedata bookletallow use to calculatethe pH of buffer solutions.
  2. 100 cm3 of a buffer ispreparedwhichcontains 0.100 mol dm-3butanoicacid and 0.200 mol dm-3sodiumbutanoate. (thepKaforbutanoicacid can be found in the data section)

pKa 4.82; pH = 5.12 (Mistake in showncalcwith extra 0)(C2)

  1. Whatisthechange in pH when 2.00 cm3 of 0.100 mol dm-3HClisadded to this buffer?

New conc = 0.0102(C2)

  1. The antiretroviral drugsTamiflu (oseltamivir) and Relenza(zanamivir) are found in Section 37 of the data booklet. Statethethe 3 funtionalgroupsthattheyhave in common.

Ester; ether; amide;

(B2)

  1. Unstablenucleiundergoradioativedecaybyemittingone of severaltypes of radiation.
  2. Thorium-234 isformedbythealphadecay of uranium. Use theselectedsection of Section 6 to write a nuclear equationforthisprocess.

(B2)

  1. Thorium-234 can undergo beta radiation. Complete thefollowing nuclear reaction.

(B1)

  1. Theisotope radium-226 has a half-life of 1620 years. Calculatetherateconstantforthedecay of thisisotopeusingtherelevantequationfromthe data booklet.

Value;(C1)

  1. The90Y isotope has a half-life of 64 hours. Use therelvantequation in Section 1 to calculatehowmuch of a 65.0 g samplewouldremainafter 4 days.

1.5 half-lives; 23 g(C2)

  1. Infraredspectroscopy can be used to detectethanol in breathsamples of “drink drivers”.

  1. Use Section 26 and yourknowledge of thestructure of ethanol to identifythe 2 importantpeaksonthisspectrum.

OH trough at 3200; CH trough at 2950(B2)

  1. Explainwhyone of thesepeakswillalso be present in thebreath of peoplewhohavenotbeendrinking alcohol.

OH in H2O

(B1)

  1. Peoplewhosufferfrom diabetes often exhale propanonevapour in theirbreath. Explainwhythismightgive a false positive resultforthepresence of alcohol?

Wouldalsogive CH peak

(B1)

  1. Describe howacifiedpotassiumdichromateisused to detectethanol in a breathalyser.

Ethanoloxidised/dichromatereduced; Colourchangefromorange to green Cr3+

(A2)

  1. Theenvironmentalimpact of thesynthesis, isolation and administration of medications are important to consider. Stateoneproblemsassociatedwitheach of thefollowing:
  2. High-level nuclear waste

Largeamount of ionizingradiationforlong time

(B1)

  1. The use of antibiotics in animal feed

Antibioticresistance

(B1)

  1. The anti-cancerdrug “Taxol” wasoriginallyisolatedfromthebark of Pacificyewtreeswhichtake 200 years to grow and are onlyfound in someparts of the US.
  2. Onecurrentmethodbeingresearched to synthesizethisdrugifthroughfermentationreactionsbysomefungi. Explainhowthiscurrentresearchisrelated to theprinciples of “greenchemistry”.

Green chemistry more environmentallyfriendly; Lesstreesharvested; fermentationprocesslessdamage; OWTTE

(B2)

  1. Themostcommonmethod of production of Taxolisnowenantioselectivesynthesisusing a chiralauxillary. Brieflyexplainwhat a “chiralauxillary” is and whyitisneeded in thissynthesis. ThestructureforTaxolisfound in the data booklet.

Isitselfanenantiomer; needed to make a chiralproduct; preventsformation of unwantedenantiomerproduct (ANY 2)

(A2)