Chemistry in your cupboard: Dettol
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Always read the label Dettol is a registered trade mark of the Reckitt Benckiser group of companies. Last reviewed by Reckitt Benckiser in 2013. Chemistry in your cupboard: Dettol Introduction One hundred and fifty years ago, before the use of antiseptics, major surgery often resulted in death from post‐operative infections. In the 1860s Joseph Lister discovered phenol could kill germs but it also causes severe skin burns. Modern antiseptics such as Dettol® have been developed based on phenol but with modifications to the chemistry to reduce the adverse effects and produce a safer product. Many antiseptics are still made based on phenol derivatives as the active ingredient. Links to the curriculum This section contains information relevant to the following areas of your chemistry curriculum: Organic chemistry Bonding Acids and bases DETTOL Antiseptics and disinfectants Before the mid‐1800s, major surgery was often a death sentence. Amputations of damaged limbs were carried out as a last resort but patients frequently died from post‐ operative infections. This changed in the 1860s when Joseph Lister developed antiseptic surgery using carbolic acid to sterilise wounds and instruments. Lister was aware of the germ theory of infections developed by Louis Pasteur and others, and knew that carbolic acid (which we now call phenol) was able to kill germs, Figure 1.
Transcript of Chemistry in your cupboard: Dettol
AlwaysreadthelabelDettolisaregisteredtrademarkoftheReckittBenckisergroupofcompanies.LastreviewedbyReckittBenckiserin2013.
Chemistryinyourcupboard:Dettol
Introduction
One hundred and fifty years ago, before the use of antiseptics, major surgery oftenresultedindeathfrompost‐operativeinfections.Inthe1860sJosephListerdiscoveredphenolcouldkillgermsbutitalsocausessevereskinburns.ModernantisepticssuchasDettol®havebeendevelopedbasedonphenolbutwithmodificationstothechemistryto reduce the adverse effects and produce a safer product. Many antiseptics are stillmadebasedonphenolderivativesastheactiveingredient.
Linkstothecurriculum
This section contains information relevant to the following areas of your chemistrycurriculum:
Organicchemistry Bonding Acidsandbases
DETTOL
AntisepticsanddisinfectantsBeforethemid‐1800s,majorsurgerywasoftenadeathsentence.Amputationsofdamagedlimbswerecarriedoutasalastresortbutpatientsfrequentlydiedfrompost‐operativeinfections.
Thischangedinthe1860swhenJosephListerdevelopedantisepticsurgeryusingcarbolicacidtosterilisewoundsandinstruments.ListerwasawareofthegermtheoryofinfectionsdevelopedbyLouisPasteurandothers,andknewthatcarbolicacid(whichwenowcallphenol)wasabletokillgerms,Figure1.
AlwaysreadthelabelDettolisaregisteredtrademarkoftheReckittBenckisergroupofcompanies.LastreviewedbyReckittBenckiserin2013.
Figure1:Anoperationinthe1870s.Doctorsareusingacarbolicacidsprayasanantiseptic.Noticethattheyappeartobewearingtheireverydayclothes!
(WellcomePhotoLibrary,WellcomeImages)
Itisreputedthatphenol’sgerm‐killingpowerfirstcametonoticeinabizarreway.Sailorswhounderwentamputationsatseaappearedtohaveahighersurvivalratethanpatientsinhospital.Thisseemedtobeduetothepracticeatseaofdippingthestumpintomoltentartosealthewound.Tarcontains,amongotherthings,phenol,Figure2.
O
H
Figure2:Structureofphenol.
Nowadays,disinfectantsarejustasimportantforgerm‐killinginhospitals,homesandelsewhere.Manyproductsarestillbasedonphenolderivativesastheactiveingredient.ThissitelooksatDettol,madebyReckittBenckiser.
StructureactivityrelationshipsPhenoliseffectiveatkillinggermsbutisotherwiseafarfromidealantisepticasitcausesnastyskinburns.Onetechniqueusedbypharmaceuticalchemistswhenfacedwiththissortofsituationistosynthesiseanumberofcompoundsrelatedtothesubstancethatisknowntobeeffective.Thisisinthehopethatoneormoreofthesecompoundswillbeasactive,orbetter,thantheoriginalbutwithfewersideeffects(such
AlwaysreadthelabelDettolisaregisteredtrademarkoftheReckittBenckisergroupofcompanies.LastreviewedbyReckittBenckiserin2013.
asskinburning).Evenbetteristhepossibilityofestablishingastructure‐activityrelationship.Thisisapatternwhichlinkssomestructuralfeatureofthemoleculewithitspharmacologicalefficiency(iehoweffectiveitisasamedicine)inasystematicway.Examplesofsucharelationshipcouldbethat
themoremethylgroupsattachedtoabenzenering,thebetterthegerm‐killingpower,or
themoreelectronegativeasubstituent,thelessharmfultotheskin.
Thisenablesthechemisttopredictwhichderivativesmightbemoreeffectiveandthereforeguidethesynthesisofnewcompounds.Figure3showssomederivativesofphenolalongwiththeirgerm‐killingpowerrelativetophenol.Allofthecompounds(exceptphenolitself)aresubstitutedphenols.Thatisthenewgrouporgroupsattachedtothebenzeneringreplaceoneormoreofthehydrogens.
OH OH
Cl
OH
Cl
Cl
OH
Cl
Cl
Cl
OH
Cl
CH3H3C
Increasing germ-killing power
1 4 13 23 280
Figure3:Therelativegerm‐killingpowerofsomesubstitutedphenols.
Question1Whatsortofstructure‐activityrelationshipissuggestedbythefirstfourcompoundsinFigure3?Suggestwhatothercompoundsmightbesynthesisedtocheckthishypothesis.Question2ThefirstcompoundinFigure3isphenolandthelastiscalled4‐chloro‐3,5‐dimethylphenol.Nametheotherthree.
AlwaysreadthelabelDettolisaregisteredtrademarkoftheReckittBenckisergroupofcompanies.LastreviewedbyReckittBenckiserin2013.
Question3a)ThebenzeneringisoftendrawnasinFigure3.Thereisahydrogenatom(notdrawn)ateach‘corner’ofthehexagonunlessthereisanotheratomorgroupattached.Thecirclerepresentsadelocalisedringofelectronsinaπorbitalaboveandbelowthering–thisiscalledanaromaticsystem.Explainwhycompoundswithanaromaticringinvariablyformsubstitutedderivativesratherthanadditioncompounds.b)Stateandexplainwhattypeofreagentsismostlikelytoattackaromaticrings.Infactthestructure‐activityrelationshipsthathavebeenestablishedforderivativesofphenolare:
the−OHgroupisrequiredforactivity; activityincreaseswithahalogeninthe4‐position(ieoppositethe−OHgroupin
thering); activityincreaseswithalkylsubstituentsofincreasedchainlength; increasedsubstitutionmakesthecompoundlesswater‐soluble;and increasedsubstitutiondecreasestoxicitytohumanswhentakenbymouth.
Phenolisalreadyaneffectivegermicide,soagreaterkillingpowerisnotreallyneeded.Whatthegreaterefficiencyof4‐chloro‐3,5‐dimethylphenolmeansisthatmuchsmallerconcentrationcanbeusedandthereforefewerside‐effectswillbeexpected.
DettolTheactivegerm‐killingingredientinDettolisinfact4‐chloro‐3,5‐dimethylphenol,alsoknownbyitsnon‐systematicnamepara‐chloro‐meta‐xylenolorPCMX,Figure4.Theprefixparaisanon‐systematicwayofindicatingthe4‐positiononthebenzenering,ieoppositethe−OHgroup.Metaindicatesthe3‐and5‐positions.
Figure4:Structureofpara‐chloro‐meta‐xylenolorPCMX.
AnumberofdisinfectantandantisepticproductsareavailableundertheDettolbrandincludingdisinfectantsforsurfaces,antisepticsforuseonthebody,wipesandsprays.Herewewillconcentrateonthe'core'product‐theliquidantiseptic,Figure5.
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Figure5:Dettolliquidantiseptic,containschloroxylenol.
Biocides,disinfectantsandantisepticsAllthetermsaboverefertogerm(iemicrobe)‐killing.Biocideisageneraltermwhichcoversactiveingredientsthatkillmicrobes.Disinfectantskillmicrobes(bacteria,fungiandviruses)andareusedonsurfaces(suchasworktops,sinksetc)butnotlivingthings(suchasskin)astheymayharmthem.Antisepticsalsokillmicroorganismsbutmaybeusedonthebodysurface(skin)althoughnotinthebody(egbymouth).
HowdoesPCMXkillbacteria?ThedetailedbiochemistryoftheactionofPCMXandotherphenol‐basedantibacterialagentsisbeyondthescopeofthissite.However,verysimply,theyareunderstoodtoworkbythe−OHgroupofthemoleculebindingtoproteinspresentonthecellmembraneofbacteria,disruptingthecellmembraneandallowingthecontentsofthecelltoleakout.
ThisallowsmorePCMXtoenterthecell,bindingfurtherwithproteinsandenzymes,andeffectivelyshuttingdownthecell’sfunctions.AthighconcentrationsofPCMX,theproteinsandnucleicacidsinthecellarecoagulatedandceasetofunction,leadingtorapidcelldeath.
Theacidityofphenols(1of3)Phenol,C6H5OH,isweaklyacidic‐itwasoncecalledcarbolicacid(nottobeconfusedwithcarboxylicacids,whichcontainthegroup−COOH).Theacidichydrogen(theonethatislostasH+whenphenolbehavesasanacid)isthehydrogenofthe−O‐Hgroup.Thisisbecauseoxygenismuchmoreelectronegativethanhydrogen(3.5onthePaulingscalecomparedwith2.1)sotheO‐HbondispolarisedOδ−‐Hδ+,makingitrelativelyeasyforthishydrogentobelostasaproton(H+ion),Figure6.
ThenegativeionformediscalledthephenoxideionandisoftenrepresentedintextasPhO−,Ph,beingusedtorepresentabenzenering,whichissometimescalledthephenylgroup.Becauseitisionic,thephenoxideionismoresolubleinwaterthanphenolitself.
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O
H
O_
+ H+
Figure6:Phenol,isalsoweaklybasic–theoxygenatomhastwolonepairs,oneofwhichcanacceptaH+iontoformtheionPHOH2+.
ThepKavalueisameasureofthestrengthofanacid(howeasilyaH+ionislost).ThelargerthepKavalue,theweakertheacid.
PCMXpKa=9.7;Ka=1.99x10−10moldm−3
phenolpKa=9.9;Ka=1.28x10−10moldm−3
ethanolpKa=15.9;Ka=7.9x10−15moldm−3
Theacidityofphenols(2of3)Imagineaweakacid,HA,whichdissociates
HA(aq)⇌H+(aq)+A−(aq)
Theequilibriumconstantisgivenby:
Kc=eqm(aq)
eqm(aq)eqm(aq)
][HA
][A][H
Foraweakacid,thisisusuallygiventhesymbolKaandcalledtheaciddissociationconstant.
Ka=eqm(aq)
eqm(aq)eqm(aq)
][HA
][A][H
pKa=–log10Ka
(ThisisanalogouswithpH=−log10[H+])
ThelargerthevalueofKa,thestrongertheacid(thegreater[H+]itproducesondissociation).However,becauseofthe−signintheexpressionabove,thelargerthevalueofpKa,theweakertheacid.
Question4ThesolubilityofPCMXis330mgdm−3anditsKais1.99x10−10.CalculatethepHofasaturatedsolutionofPCMX.
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Theacidityofphenols(3of3)Whyisphenolsomuchmoreacidicthanethanol?Inotherwords,whyistheHoftheOHgroupofethanolsomuchlesslikelytobelostthanthatoftheOHgroupofphenol?
C2H5OH⇌C2H5O−+H+
TheanswerliesintherelativestabilitiesofthenegativeionsleftafteraH+ionhasbeenlost.Intheethoxideion,thechargeremainslocalisedontheoxygenatom.Inthephenoxideion,PhO−,thenegativechargeisspreadoverthebenzeneringduetooverlapofap‐orbitalontheoxygenatomwiththedelocalisedπ‐systemofthebenzenering,Figure7.
Figure7:Delocalisationinthephenoxideion.
Inthetopdiagram,theoxygenatomisshownhybridisedsp3(seenextpage)withapairofelectronsineachofthethreeblueorbitals.(Thefourthsp3‐orbitalisinvolvedinformingaσ‐bondwiththecarbonatomontheringtowhichitisattached.)Inthemiddlediagram,theoxygenatomisshownhybridisedsp2withthep‐orbitalverticalreadytooverlapwiththearomaticsystem.Inthebottomdiagram,theoxygenatomishybridisedsp2,itsunhybridisedp‐orbitalhasoverlappedwiththe‘doughnut‐shaped’delocalisedorbitalofthebenzeneringandthenegativechargeisspreadoverthering.
HybridisationHybridisationisaconceptusedtohelpexplaintheshapesofmolecules.Itisbasedontheideathatanyatom,orbitalsofsimilarenergysuchas2sand2pcan‘mixtogether’to
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producethesamenumberofneworbitalsofadifferentshape.Thesehybridorbitalscanthenformbondsbyoverlappingwithorbitalsonotheratoms.
Forexampleincarbon,oxygenandnitrogen,wheretheorbitalsinvolvedinbondingarethe2sand2p‐orbitals,theymaymixinthreeways.
1. s+3xp→2xsp+2xp2. s+3xp→3xsp2+1xp3. s+3xp→4xsp3
Thenotationsp,sp2andsp3givestheproportionofsandporbitalsinthehybrid.Forexample,ansp3is¼sand¾p.Noticethattheoriginalfourorbitalsalwaysgiverisetofournewones.TheshapesareshowninFigure8.
Figure8:Formationofhybridorbitals‐thethreepossibilities.
Theanglesbetweenthehybridisedorbitalsareimportantastheyhelptoexplaintheshapesofmolecules.Thesporbitalsareat180°tooneanother,thesp2at120°andthesp3pointtothecornersofatetrahedron(109.5°).
Hintsp2ispronounced‘esspeetwo’not‘esspeesquared’.
Makingtheactiveingredientsoluble(1of3)PCMXis,asexpected,notverysolubleinwater;only330mgdm−3.
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Question5WhywouldyouexpectPCMXtoberelativelyinsolubleinwater?Thisisbecauseonlythe–O‐Hgroupcanformhydrogenbondswithwater.
Question6Drawadiagramtoshowhowawatermoleculecanformahydrogenbondwithaphenolmoleculea)viaahydrogenatomonthewater.b)viaanoxygenatomonthewater.
Becausetheyareacidic,phenolsandsubstitutedphenolsaremoresolubleinalkalinesolutions.However,stronglyalkalinesolutionsarecausticanddamagetheskinsoaslightlyalkalinesolution,pH10,isused.Infact,PCMXshowsslightlylessactivityatpH10thaninaneutralsolution.
Dettolactuallycontains4.8%w/vPCMX.
w/vstandsforweightperunitvolume,sothisis4.8gin1000cm3or48gdm−3(48,000mgdm−3),nearly150timesasmuchasitssolubilityinpurewater.Howisthisachieved?
PCMXissolubleinrelativelynon‐polarsolvents‐onesuchispineoilwhichisusedintheformulationofDettol.Thisoilisderived,notsurprisingly,fromneedles,twigsandconesofpinetrees.Pineoilisamixturecomposedlargelyofalpha‐terpineol,whichismoderatelypolarbecauseofitssingle−OHgroup,Figure9.
Figure9:Structureofalpha‐terpineol.
Therestofthepineoilconsistslargelyofhydrocarbons.Itcontainsterpenes,agroupofhydrocarbonswhichareessentiallypolymersofisoprene,Figure10.
Figure10:Structureofisoprene.
AlwaysreadthelabelDettolisaregisteredtrademarkoftheReckittBenckisergroupofcompanies.LastreviewedbyReckittBenckiserin2013.
Question8 Whatisthemolecularformulaofisoprene? Whatistheempiricalformulaofisoprene?
Question9Whatisthesystematicnameofisoprene?
Makingtheactiveingredientsoluble(2of3)TheanswertoincreasingthesolubilityofPCMXistouseasoap.
Soapsanddetergentshave‘tadpole‐shaped’moleculesinthattheyhaveanon‐polar‘tail’andapolarorionic‘head’.The‘tail’canformvanderWaalsbondswithnon‐polarmoleculeswhilstthe‘head’canformhydrogenbondswithwater.Thisisanexampleofthe‘likedissolveslike’rule.
ThesoapusedinDettolismadefromcastoroilwhichcontainsricinoleicacid(systematicname12‐hydroxy‐(cis)‐9‐octadecenoicacid),Figure11.
OH
O
OH
Figure11:Structureofricinoleicacid.
Question10Explainthesystematicname12‐hydroxy‐(cis)‐9‐octadecenoicacid.Historically,thepositionsofsubstituentsarounddoublebondshavebeenindicatedbythetermscis(onthesameside)andtrans(ontheoppositeside).
Analternativenotationmakesitpossibletodealwithmorecomplexcases.TheE‐Znotationisbasedonatomicnumbers.Welookattheatomsattachedtoeachofthecarbonatomsinthedoublebond.Whenthetwoatoms(ofeachpair)ofhigheratomicnumberareonthesamesideoftheC=C,theisomerisdescribedasZ,fromtheGermanwordfortogether,zusammen.IfnotitisE,fromtheGermanwordforopposite,entgegen.
So,ifthetwoatomswiththegreatestatomicnumberareonthesamesideofthedoublebondasinricinoleicacid,theconfigurationisZ.
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Makingtheactiveingredientsoluble(3of3)Thericinoleicacidisreactedwithsodiumhydroxidetoformtheionicsaltsodiumricinoleate.Thissalthasanionicheadandalargelynon‐polartail–theclassicshapeofadetergentorsurfactantmolecule,seeFigure12.
OH
O
O- Na+
Ionic 'head'
Non-polar 'tail'
Figure12:Structureofsodiumricinoleate.
Inthebottle,DettolconsistsofanalmostclearliquidinwhichthePCMXisheldinsolutionbythesodiumricinoleate.
Ondilutioninwater,however,acloudyliquidforms.ThisconsistsofdropletsofpineoilcontainingdissolvedPCMX.Thesearehelddispersedinwaterbyalayerofsoapmoleculesarrangedwiththeirtailsinthepineoilandtheirheadsinthewater,Figure13.Thesedropletsarebigenoughtoscatterlight,hencethecloudinessofthesuspensionwhichiscalledanemulsion.
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Figure13:PCMXinaqueoussolutionexistsinanumberofforms.
ThePCMXinthedropletsofpineoilisnotavailabletokillbacteria‐itisthefreeaqueousPCMXthatdoesthis.However,anequilibriumexistsbetweentheemulsifiedPCMXinthedropletsandfreePCMXdissolvedinthewater.AsPCMXisusedupinkillingbacteria,moreisreleasedfromthedropletstokeeptheaqueousPCMXconcentrationessentiallyconstant.SothedropletsactasareservoirofPCMX.
Question11WhatchemicalprinciplepredictsthatastheaqueousPCMXisusedup,morewilldissolvefromthedropletsandthemicellestomaintainitsconcentration?ThereisafurtherreservoirofPCMXinso‐calledmicelles.Thesearegroupsofsoapmoleculesclusteredtogetherwiththeirnon‐polartailsentwined.Non‐polarPCMXmoleculescanexistinsidethesemicellesandbereleasedinasimilarwaytothoseinthedroplets.AlsoinsolutionarefreesoapmoleculeswhichinfactaidthepenetrationofPCMXintothebacterialcellwalls.Inaddition,pineoilitselfhasamildantibacterialaction.
Pineoilalsohasapleasantsmellofpineandovertheyears,thishasbecomeassociatedinthemindofthepublicwithantisepticanddisinfectantaction,somuchsothatmostdisinfectantproductsareformulatedwithapinesmell.
Althoughimprovementshavebeenmadeovertheyears,thebasicformulationofDettolandsimilarproductshasremainedthesamesincethe1930s.
OtheringredientsandformulationsThereareanumberofotheringredientsintheformulationofDettolincludingpropan‐2‐ol(isopropanol),Figure14.
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Figure14:Structureofpropan‐2‐ol(isopropanol).
ThishelpstomakethePCMXsolubleinwaterandhelpstostabilisethemicelles.Caramelgivestheproductitsyellow‐browncolour.
AswellasDettolliquidantiseptic,Dettolbrandedproductsaresoldinanumberofotherformswithdifferentformulations.MostoftheDettolproductsarenotmedicinesandthereforedonothaveregisteredactives,Figure15.
Figure15:DifferentformsandformulationsofproductssoldundertheDettolbrand.
FurtherinformationDettolissoldintheUKbyReckittBenckiser(www.dettol.co.uk).Thereareotherbrandedproductswhichworkinasimilarway.
AcknowledgementsTheRoyalSocietyofChemistrywishestothankReckittBenckiserforhelpinpreparingthismaterial.
AlwaysreadthelabelDettolisaregisteredtrademarkoftheReckittBenckisergroupofcompanies.LastreviewedbyReckittBenckiserin2013.
TheRoyalSocietyofChemistrygratefullyacknowledgesthatthisprojectwasinitiallysupportedbyReckittBenckiserin2007.ReckittBenckiserconductedafinalreviewin2013sopleasenotethatcertaininformationmaybeoutofdate.
QUESTIONSANDANSWERSQuestion1Whatsortofstructure‐activityrelationshipissuggestedbythefirstfourcompoundsinFigure3?Suggestwhatothercompoundsmightbesynthesisedtocheckthishypothesis.Itsuggeststhatthemorechlorinesubstituents,thegreaterthegerm‐killingactivity.Morehighly‐substitutedderivativescouldbemade,suchas2,3,4,5‐tetrachlorophenol.
Question2ThefirstcompoundinFigure3isphenolandthelastiscalled4‐chloro‐3,5‐dimethylphenol.Nametheotherthree.2‐chlorophenol;2,4‐dichlorophenol;2,4,6‐trichlorophenol.
Question3a)ThebenzeneringisoftendrawnasinFigure3.Thereisahydrogenatom(notdrawn)ateach‘corner’ofthehexagonunlessthereisanotheratomorgroupattached.Thecirclerepresentsadelocalisedringofelectronsinaπorbitalaboveandbelowthering–thisiscalledanaromaticsystem.Explainwhycompoundswithanaromaticringinvariablyformsubstitutedderivativesratherthanadditioncompounds.Aromaticcompoundaremorestablethanexpectedduetothedelocalisedringofsixelectrons.Formingadditionproductswouldrequireoneormoreoftheseelectronstobeusedinformingbond(s)withaddedgroup(s)andthereforedestroythearomaticstability.
b)Stateandexplainwhattypeofreagentsismostlikelytoattackaromaticrings.Electrophiles.Theseattackthehighelectron‐densityofthedelocalisedsystemofelectrons.
Question4ThesolubilityofPCMXis330mgdm−‐3anditsKais1.99x10−10.CalculatethepHofasaturatedsolutionofPCMX.
Ka=eqm(aq)
eqm(aq)eqm(aq)
][HA
][A][H
330mg=0.33g
0.33/156.6mol=2.11x10−3molin1dm3
ietheinitialconcentrationofPCMX,[PCMX(aq)]=2.11x10−3moldm−3.
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PCMX→H++PCMX−
1.99x10−10=eqm(aq)
eqm(aq)eqm(aq)
][PCMX
][PCMX][H
SincesomePCMXdissociates,[PCMX(aq)]eqm=[PCMX(aq)]–[H+(aq)]eqm
So1.99x10−10=eqm(aq)eqm(aq)
eqm(aq)eqm(aq)
]H][PCMX
][PCMX][H
[
Since[H+(aq)]eqm=[PCMX‐(aq)]eqmand[H+(aq)]eqmissmall
1.99x10−10=eqm(aq)
eqm2
(aq)
][PCMX
][H
1.99x10−10= 3-
eqm2
(aq)
10 x 2.11
][H
[H+(aq)]2eqm=4.2x10−13
[H+(aq)]eqm=6.48x10−7moldm−3
pH=−log10[H+]=6.19
Question5WhywouldyouexpectPCMXtoberelativelyinsolubleinwater?TheonlypolarpartofthemoleculewhichcanhydrogenbondtowatermoleculesistheOHgroup,therestisnon‐polarandunabletointeractstronglywithpolarwatermolecules.
Question6Drawadiagramtoshowhowawatermoleculecanformahydrogenbondwithaphenolmolecule
viaahydrogenatomonthewater
viaanoxygenatomonthewater
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Question7Writeoutthestructuralformulaofisopreneusingadisplayedformula
C
C
C
C
H H
C
H
H
H
H
H
H
Question8
Whatisthemolecularformulaofisoprene? Whatistheempiricalformulaofisoprene? C5H8 C5H8
Question9Whatisthesystematicnameofisoprene?2‐methylbuta‐1,3‐diene
Question10Explainthesystematicname12‐hydroxy‐(cis)‐9‐octadecenoicacid.
octadecindicatesthatthereare18carbonatoms
oicacidindicatesacarboxylicacid(COOH)functionalgroup
eneindicatesanalkene,acarbon‐carbondoublebond(C=C)
the9indicatesthepositionoftheC=Cbetweencarbons9and10(countingfromtheCOOHendofthemolecule)
hydroxyindicatesanalcohol(OH)functionalgroup
the12indicatesthattheOHgroupisoncarbon12(countingfromtheCOOHendofthemolecule)
cisindicatesthatbothchainsattachedtotheC=Careonthesameside
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Question11WhatchemicalprinciplepredictsthatastheaqueousPCMXisusedup,morewilldissolvefromthedropletsandthemicellestomaintainitsconcentration?LeChatelier’sprinciple.
