An Analysis of Mass Spectral Isotope Patterns of Compounds ：化合物的质谱同位素模式分析

TheChlorineRule:AnAnalysisofIsotopePatternsofCompoundsContainingMultipleBromineandChlorineAtomsRayA.Gross,Jr.WithanIntroductiontotheIsotope-PatternAnalyzerMyReasonsforthisPresentationPresentresultsobtainedatPGCCShowthatcontentfoundintextbookscanbeimprovedMotivatestudentsIsotopesofBrandClaLowmassbHighmassRatio(a/b)RoundedratioVariable#atomsBr79(50.69)81(49.31)1.0281:1mCl35(75.78)37(24.22)3.1293:1nMassSpectrometerSchematicdiagramofamassspectrometerWhyBrandCl?Molecular-ionpeaksofC10H20Br1Cl1,C10H19Br2Cl1andC10H18Br3Cl1.PremiseInlieuofpatternmatching,itshouldbepossibletodeterminethenumberofBrandClatomsinamolecularformulaofacompoundbyanalyzingthemolecular-ioncluster(i.e.,byclusteranalysis).HerbertC.BrownNobelLaureateHydroboration-oxidationwithBH3(CHM201)ReductionwithNaBH4(CHM202/204)LillianBergNVCC-AnnandaleChlorineConstantBromineConstantIM=3nTheoreticalConsiderationsIdealCompoundsBr(a:b)=1:1Cl(a:b)=3:113Cand2HnegligibleBromineBinomialRatio(a:b)=1:1(1a+1b)mforBrm(1a+1b)1=1a+1b=1:1(1a+1b)2=1a2+2ab+1b2=1:2:1ChlorineBinomialRatio(a:b)=3:1(3a+1b)nforCln(3a+1b)1=3a+1b=3:1(3a+b)2=9a2+6ab+1b2=9:6:1IdealModel=BinomialPair(1a+1b)m(3a+1b)nBr1Cl13a2+4ab+1b2=3:4:1Results(1a+1b)m(3a+1b)n=1m3na(m+n)+….+1m1nb(m+n)I(L/R)=1m3n/1m1nIM=3nChlorineRule:WhenIequals1,3,9,27or81;nis0,1,2,3,or4,respectively,wheren=numberofchlorineatoms.ThenumberofbromineatomsmequalsA–n.J.Chem.Educ.2004,81,1161-1168(articleavailableatfrontdesk)RoaldHoffmann-NobelLaureateConservationoforbitalsymmetry“Oxygen”PriestleyvsSheeleHoffmannDjerassiWoodwardGrossgivinglecturewithHoffmann,DjerassiandWoodwardlookingon.StructureBegetsPropertiesLet’sexaminestructures.Assume3:1and1:1isotopicabundancesofchlorineandbromine.ConsiderBrm,ClnandBrmClncompounds.ResultsN=2m4nN=2m2n2nN=2A2nChem.Educ.2003,8,182-186Derivedachlorine-ruleequation,IM=3nAppliedittofindgrossstructuresofunknownsDerivedaunit-sampleequation,N=2A2nSummaryPartIforBrmClnCompoundsFollow-ontotheChlorineRuleAnautomatedA+2isotope-patternanalyzer(IPA)IPAisonmywebsiteJ.Chem.Educ.,inpressExampleofaPrintOutofaMassSpectrumintheMolecular-IonRegionMolecular-IonDataisEnteredintotheIPATheExcelprogramreturnstheA+2(Cl,Br,S)compositionofthemolecularformulaHomeworkAssignmentforSelectedStudentsPickupslipfromfrontdeskEnterdatafromyourslipintoIPAObtaintheCl,Br,Scomposition(e.g.,Br1Cl2)andrecorditonyourslipWriteyournameontheslipandturnitinnextTuesday.Acknowledgement:MassSpectrafromtheSpectralDataBaseSystem(SDBS)EndeLectureattendedbyhordesofstudentseagertolearn.GrossandFriends