Name:MohitN.Mulani ExperimentDueDate:2/20/14

Sectioninstructor:BrianKasper Section:231

LuminolandChemiluminescence

1)In3nitrophthalicacid,thecarboxylicwhichismoreacidicisatthe2positionwithpKa=2.

Inthisconjugatedringsystem,thenitrogroupactsasapowerfulelectronwithdrawinggroup

(deactivatingagent)whichservestoremove/pullawayelectrondensityfromthecarboxylicacidgroups

andmakethemmoreelectrophilicwhichstabilizestheconjugatebase(anion)andmakesiteasierforit

tolosetheH+.Thiseffectofthenitrogroupisfeltmuchmorestronglybythecarboxylicgroupcloserto

itontheorthoposition(w.r.tit)thantheotheroneinthemetapositionmakingitmoreacidic.

2)TocalculatetheKeq,weneedthepKavaluesoftheacidandtheconjugateacid.Wehaveoneof

these(for3nitrophthalicacid:2)andtofindtheother,wecanusethepKbvalueofHydrazinewhichis

5.77.AsthesumofthepKbandpKavaluesforaconjugatepairis14,wecancalculateittobe8.23.

Makingdissociationequationsfortheacidsanddividingthemtogettheoriginalreaction,weseethat

pKeqis28.23=6.23.Keqthereforeis106.23or1.7x106.

3)Thereactionof3nitrophthalicacidandHydrazinecouldgobothwaysbutonlytheonewhich

involvesthereplacementoftheOHgroupwithaminegroup(NH)andthentheintramolecular

replacementoftheotherOHgroupof3nitrophthalicacidwiththeotheraminegroupisfavoured.This

reactionismorelikelytohappenbecauseasitisintramolecular,itisfasterthantheminoronewhich

involves2moleculesofhydrazineattackingtheseparateOHgroups.Wevealsoestablishedthat

becauseofitspositionrelativetothenitrogrouponeofthecarboxylicgroupsismoreacidicwhich

makesitmorelikelytobetheonewhichisattackedfirstfollowedbyanintramolecularreaction.

4)ThepKbvalueforethant1,3diamineishigherthanthatofhydrazine(itisaweakerbase)which

meansthesubsequentpKaoftheconjugateacidwillbesmallermakingitsKeqhigher.Thislowersthe

Keqoftheoriginalreaction(whichiscalculatedastheratioofacidKeqandconjugateacidKeqimplying

thattherateofforwardreactionhasbeenlowered.Theproductformedasaresultofreactingtheacid

withethane1,3diaminewillbeamuchlargerringastheamidegroupnowattacksthecarboxylicacid

forminganeightmemberedring.Eightmemberedringsascomparedtosixmemberedrings(nostrainin

chairconformation)orfivememberedrings(onlytorsionalstrain)havebothtorsionalstrainandsteric

strain.Thismakesitmoreunstable.

5)Thisoccursbecauseamidesarelessbasicthanaminesonaccountofresonancestabilization.The

resonanceoccursduetothepresenceofalonepaironNitrogenwhichisdelocalizedbetweenitandthe

electronegativeoxygenofthecarbonylgroup.

6)485nm.TheluminolontreatmentwithK3Fe(CN)6/H2O2emitslightwhichhasabrightblue(almost

cyan)colourwhichcorrespondstothehighendofthebluewavelength(450500nm),edgingtowards

greenratherthanviolet.Thislightwouldbeamixtureofseveralwavelengthsaroundthehigherendof

thisrangesoIselected485nm.

7)Itwouldbeaterriblelightsourcebecauseoftheshorttimeitsglowlasts(onlyafewseconds).This

wouldmeanconstantreactionsofluminolwithoxidisingagentswhichiscostlyanddifficultifthesignis

torun24hoursaday.

8)A)Luminol:Exactmass177.05g

Massoftwomostabundantisotopes:177.05g,178.06g.

Luciferin:Exactmass280.00g

Massoftwomostabundantisotopes:280.00g,281.00g.

B)Luminolwouldhaveauniquesignalataround3000cm1associatedwiththeNHgroupand

Luciferinwouldalsohavearecognizablesignalduetothepresenceofsulphursinglebondedtocarbon

initsheterocyclicsystem.

C)Luminolhas7signals(with2uniquecarbonsatthecentreofthebicyclicsystemhavingthesame

energywithashiftdifferenceofabout1ppm)andLuciferinhas11signalswithdifferentchemicalshifts.

D)Luminolhas5signalsandLuciferinhas8signals.