2b Summer2015 MS Slides Notes

IntroductoryOrganicChemistryChem 222&Chem 234

Summer2015

Dr.LauraPavelkaDepartmentofChemistry

Pulp&[email protected]

CHAPTER9:TOOLSFORSTRUCTUREDETERMINATION

CHEM222/234 LectureChapter9 2

NOWTHATWEHAVEAHANDLEON13C&1HNMRSPECTROSCOPY

TIMETOMOVEONTOMASSSPEC!

LectureChapter9

LETS SEEWHATELSEWECANDO...

Section2 NMRSpectroscopyandMassSpectrometryChapter9 ToolsforStructureDetermination(Part2)

IntrotoMassSpectrometry(MS)IonizationandFragmentationIsotopesinMSIntegratedStructureDetermination

CHEM222/234 3

MassSpectrometry


MassSpectrometry electromagneticradiationNOTinvolved

Spectroscopy studying/plottingtheinteractionofmoleculeswithelectromagneticradiation

MassSpectrometry


UsesofMassSpectrometry:1. MolecularWeightand/orFormulaDetermination2. StructuralAnalysis fragmentationpatterns3. IsotopeAnalysis

MassSpectrometry electromagneticradiationNOTinvolved

Spectroscopy studying/plottingtheinteractionofmoleculeswithelectromagneticradiation

TypicalMassSpectrum


KeyFeaturesofaMassSpectrumA. Mass/ChargeRatio formulaweightofeachionfragmentproducedB. IonAbundance amountofeachionfragmentproduced(%)C. BasePeak mostabundantionfragment(tallestpeak)D. MolecularIon unfragmented ion(originalformulaweight)E. IsotopePeaks molecularionscontainingheavierisolopes (ex.13C)

LectureChapter9




CHEM222/234 7

MassSpectrometry


sampleinlet

sampleinlet

ionizationchamberionizationchamber

massanalyzermass

analyzer

CollectinganMassSpectrum: ionizecompound(electronbeamcommon ElectronImpactMS) sendthroughmassanalyzer(magnetortimeofflightToF)

detectordetector

EIMS:Ionization


ex.IonizationofPropane

*electronremovedfromnonbondingandelectronseasiest*

Fragmentation:BondCleavage


RadicalCation

Cation +Radical

Radical+Cation

TwoPossibleCleavageOptions:

*stabilityofcation determinesrelativeabundanceoffragments*(highlysubstituted/resonancestabilizedR+ formedmore!)

Practice:Ionization/Fragmentation




ex.Hexane



ex.CH3F

Practice:Fragmentation


IdentifytheM+peakandbasepeakintheMSofethylbenzene.Whatfragmentgivesrisetothebasepeak?



Ethers



Aldehydes



CarboxylicAcids



OftenNOMolecularion

Alcohols



Halides

Practice:AlcoholFragmentation


MW:88.15g/mol

Practice:AlkeneFragmentation


MW:84.16g/mol

LectureChapter9




CHEM222/234 22

IsotopePeaksandMolecularIon


m+1

m+2


12CH4 13CH4


m+1:13C(and15N)IsotopePeaks

OneCarbon:Methane(CH4)

RatioMW

98.916

1.117




OneCarbon:Methane(CH4)

13C~1.1%naturalabundance



LargerMolecules(>1carbon)

1.1%x3(possible13Clocations)+0.37%x2(possible15Nlocations)


1.1%x5(possible13Clocations)



DeterminingMolecularFormulas(#ofCarbons)


Intensity[M+ +1]peak x100=max#carbonsIntensity[M+]peak

13C~1.1%naturalabundance

Practice:Determining#Carbons


EstimatethenumberofcarbonspresentinthecompoundthatproducedthefollowingMS.



m+2:34S,37Cl,or81BrIsotopePeaks

OneSulfur:Methanethiol (CH3SH)

CH332SH CH334SH

RatioMW

9548

450




OneChlorine:Chloromethane(CH3Cl)

CH335Cl CH337Cl

RatioMW

7550

2552




OneBromine:Bromomethane (CH3Br)

CH379Br CH381Br

RatioMW

5094

5096



m+4:Twoof34S,37Cl,or81BrIsotopePeaks

TwoBromines:Dibromomethane (CH2Br2)

CH279Br2 CH281Br2

Ratio

MW

25

172

25

176

CH279Br81Br

50

174

Nitrogen (Even Electron)Rule


Nitrogen Rule even mass(M+)=even number ofnitrogens (including zero)odd mass(M+)=odd number ofnitrogens

*mostly odd massfragmentsforeven massM+ **mostly even massfragmentsforodd massM+ *

M+M F1+ F2+

odd odd eveneven even odd

Nitrogen (Even Electron)Rule


Nitrogen Rule even mass(M+)=even number ofnitrogens (including zero)odd mass(M+)=odd number ofnitrogens

*mostly odd massfragmentsforeven massM+ **mostly even massfragmentsforodd massM+ *

Practice:DeterminingMolecularFormula


Whatisapossibleformulaforthiscompound?


NOWTHATWEKNOWABOUTIR,13C&1HNMRSPECTROSCOPYANDMASSSPECTROMETRY

YOURCANTRYSOMEINTEGRATEDEXAMPLESANDSOLVEUNKNOWNS!

LectureChapter9




CHEM222/234 39

StructureDetermination


ORGANICSYNTHESISORGANICSYNTHESIS

ISOLATIONOFNATURALPRODUCTS

ISOLATIONOFNATURALPRODUCTS

STRUCTUREDETERMINATION&

ANALYSIS(MS,IR,NMR)

STRUCTUREDETERMINATION&

ANALYSIS(MS,IR,NMR)

StructureDetermination


1. MS molecular weight/formulaandunits ofunsaturation2. IR identificationofpolarfunctional groups(OH,NH,C=O,etc)3. 13CNMR #typesofcarbons,possiblechemical environments4. 1HNMR #typesofhydrogens,possiblechemical environments,number

ofeach typeofhydrogen,number ofneighbouring hydrogens

MSMS IRIR13CNMR13CNMR

1HNMR1H

NMRSTRUCTURE!STRUCTURE!

EXTRAPRACTICEhttp://www.chem.ucla.edu/~webspectra/

Practice:IntegratedExample


SupposetheIRspectrumofthecompoundthatgaverisetotheMSbelowcontainsastrongabsorptionat1670cm1 andnoabsorptionsabove3000cm1.Drawthreepossiblestructures.



AnunknownhastheMSbelow.Thiscompoundalsohasa13CNMRspectrumthatcontainsfoursignalsandanIRspectrumwithanintensepeakat1720cm1.Proposeastructure.



1HNMRZOOM(6.0 7.3ppm)

AcompoundhastheformulaC8H9NO2.Labelallpeaksandproposeastructure.




1HNMRZOOM(6.0 7.3ppm)



AcompoundhastheformulaC9H10O3.Labelallpeaksandproposeastructure.

Chapter9(MS):MainObjectives


1. UnderstandbasicsofMStheory(ionizationandfragmentationofcommonfunctionalgroups).

2. Useamassspectratohelpelucidatethestructureofanunknown(findmolecularweight/formula).

3. Recognizebasepeakandmolecularion.4. RecognizeisotopepatternsforC,S,Cl,Br.5. UseNitrogen/EvenElectronRuletodifferentiate

fragmentsfromM+ anddetermineeven/odd#Ns.

Chapter9:MSSummary


IntrotoMassSpectrometry(9.13)IonizationandFragmentation(9.149.16)IsotopesinMS(9.17)IntegratedStructureDetermination

CHEM222/234 50LectureChapter9

Chapter9:MSPractice



AssignedProblems(Solomons,10th Edition):9.16 9.19,9.21,9.22,9.32,9.33,9.37 (MS)9.39 9.47 (Integrated)14.14,14.30 14.39 (Integrated Aromatic)

AssignedProblems(Solomons,11th Edition):9.17 9.21,9.31,9.32,9.36 (MS)9.38 9.46 (Integrated)14.14,14.30 14.39 (Integrated Aromatic)

Sapling(ExtraPractice):Ch 9Assignment

2b Summer2015 MS Slides Notes

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