Biology 2005N Paper 3 Option H

http://lawrencekok.blogspot.com

Prepared by Lawrence KokTutorial on Mass Spectrometry, Isotopes Identification and Index Hydrogen Deficiency

Index Hydrogen Deficiency (IHD) = Degree unsaturation H H H H H H H - C - C C C C C H H H H H H H H H H H H H H - C - C = C C C C H H H H H H H H H H H H - C - C C = C C C H H H H HHexaneC6H14 IHD = 0Hex-2-eneC6H12 IHD = 1Hex-3-eneC6H12 IHD = 1CyclohexaneC6H12 IHD = 1

How many double bonds/rings presentAny double/triple bond/cyclic - number hydrogen atoms decreaseHow many H2 need to convert molecule to saturated/non cyclic Saturated hydrocarbon = CnH2n+2SaturatedIDH = 0Unsaturated(1 bond)2 H deficiency IHD = 1 H H C = C H H

Unsaturated(2 bond)4 H deficiency IHD = 2

Unsaturated(1 ring)2 H deficiency IHD = 1

Unsaturated(3 bond) + 1 ring8 H deficiency IHD = 4IHD = 11 bond or 1 ring structureUnsaturated(2 bond) + 1 ring6 H deficiency IHD = 3

Unsaturated(4 bond) + 1 ring10 H deficiency IHD = 5IHD = 22 bond / 1 bond + 1 ringIHD = 33 bond / 2 bond + 1 ring / 1 bond+ 2 ringUnsaturated(4 bond) + 1 ring10 H deficiency IHD = 5Unsaturated(6 bond) + 2 ring16 H deficiency IHD = 8

Click here IHD (Khan Academy)

Index Hydrogen Deficiency (IHD) = Degree unsaturation

H H H H H H H - C - C C C C C H H H H H H HHexaneC6H14 IHD = 0Hex-2-eneC6H12 IHD = 1Hex-3-eneC6H12 IHD = 1CyclohexaneC6H12 IHD = 1

How many double bonds/rings presentAny double/triple bond/cyclic - number hydrogen atoms decreaseHow many H2 need to convert molecule to saturated/non cyclic Saturated hydrocarbon = CnH2n+2IHD = 11 bond or 1 ring structure

IHD = 22 bond / 1 bond + 1 ringIHD = 33 bond / 2 bond + 1 ring / 1 bond+ 2 ringMolecule with C and HMolecule with N, O, S or Halogen

C6H12C2H2

or

(1 bond / 1 ring)(2 bond)C2H3CIC5H7N

H - C = C - CI H H (1 bond)

(3 bond / 2 bond + 1 ring)or H H H H H H H - C - C = C C C C H H H H H H H H H H H H - C - C C = C C C H H H H H H H H H H H H - C - C = C C C C H H H H H

MoleculeIndex H2 DeficiencyC2H22

Oxygen and Sulfur - No effect on IHDHalogen - like H CHCI3 = CH4 , C2H5CI = C2H6Nitrogen add one to C and one to H - CH5N same IHD as C2H6Index Hydrogen Deficiency (IHD) = Degree unsaturationHow many double bonds/rings presentAny double/triple bond/cyclic - number hydrogen atoms decreaseMolecule with N, O, S or Halogen

Click here IHD video

MoleculeIndex H2 DeficiencyC2H41

MoleculeIndex H2 DeficiencyC2H4O1

MoleculeIndex H2 DeficiencyC2H5CI0

MoleculeIndex H2 DeficiencyC6H64

MoleculeIndex H2 DeficiencyC7H6O25

MoleculeIndex H2 DeficiencyC7H9N2CI33

MoleculeIndex H2 DeficiencyC4H9N1

MoleculeIndex H2 DeficiencyC6H9NOCI22

MoleculeIndex H2 DeficiencyC4H8CIF0

Click here IHD (Khan Academy)

MoleculeIndex H2 DeficiencyC6H12O61

Halogen

Click here spectroscopy database (NIST)Weighted average calculationRAM calculationVideo on IsotopesVideo on weighted averageRelative Atomic MassWeighted average mass- due to presence of isotopesRelative Isotopic Mass, (Ar) of an element:Relative isotopic mass = Average mass of one atom of element 1/12 x mass of one carbon-12 Relative isotopic mass, carbon = 12.01

RAM = 12.01Relative Abundance13Why RAM is not a whole number? Relative Isotopic Mass:= (Mass 12C x % Ab) + (Mass 13C x % Ab) = (12 x 98.9/100) + (13 x 1.07/100) = 12.01

Video on Isotopes

12Isotopes are presentCCC12.01

98.9% 1.07%

Click here spectroscopy database (Ohio State)

Mg - 3 Isotopes

24 Mg (100/127.2) x 100% - 78.6%25 Mg (12.8/127.2) x 100% - 10.0%26 Mg (14.4/127.2) x 100% - 11.3% Relative Isotopic Mass:= (Mass 24Mg x % Ab) + (Mass 25Mg x % Ab) + (Mass 26Mg x % Ab)= (24 x 78.6/100) + (25 x 10.0/100) + (26 x 11.3/100) = 24.30Relative Abundance% AbundancePb - 4 Isotopes

204Pb (0.2/10) x 100% - 2%206Pb (2.4/10) x 100% - 24%207Pb (2.2/10) x 100% - 22%208Pb (5.2/10) x 100% - 52% Relative Isotopic Mass= (Mass 204Pb x % Ab) + (Mass 206Pb x % Ab) + (Mass 207Pb x % Ab) + (Mass 208Pb x % Ab)= (204 x 2/100) + (206 x 24/100) + (207 x 22/100) + (208 x 52/100) = 207.20Convert relative abundance to % abundanceConvert relative abundance to % abundanceRelative Abundance% AbundanceRelative Isotopic Mass24 25 26 24 25 26MgMg

Mass SpectrometerUses mass spectrometerPresence of isotopes and its abundance Relative atomic mass of an elementRelative Molecular mass of a molecule Structure of organic compound Distinguish bet structural isomers

CH3CH2CH2OH OH |CH3CHCH3 CH3 |CH3C-CH3 | CH3CO2structural formula

Organic structure determination

24 25 26 MgMg

Detail notes from chem msuClick here notes from chemguideMass Spectrometer

Parts of Mass SpectrometerSample injectionVaporization Chamber Sample heat to vapour state Ionization Chamber Molecule bombard with electron form positive ion Accelerator Chamber M+ ion accelerated by Electric field Deflector M+ ion deflected by magnetic field Detector Convert abundance of M+ ion to current. M+ ion neutralize by electron (more e need - higher current higher intensity of peak) Intensity of peak show -relative abundance of ion Sample X bombard by electron Form positive M+ ion Accelerated (Electric Field) Deflected (Magnetic Field) and Detected X + e- X+ + 2e-

Vaporization Ionization Accelerator Deflector Detector 321542134

5

Click here for simulationMass SpectrometerParts of Mass SpectrometerVaporization Ionization Accelerator Deflector Detector 32154

VaporizationInjection/ vaporization of sampleliquid state gaseous IonizationForm cation, M+ AccelerationM+ ion accelerate by Electric fieldDeflectionM+ ion deflectby magnetic field

Deflection depend: mass/charge (m/z) ratio:(m/z) ratio HIGH - Deflection LOW Deflection depend:mass/charge (m/z) ratio:(m/z) ratio LOW- Deflection HIGH 37CI+35CI+35CI2+23415 Detector Convert abundance M+ ion to current. M+ ion neutralize by electron (more e need - high current high intensity of peak) Peak Intensity relative abundance of ion

Video Mass spectrometer Video Ionization/fragmentation Video how MS works

Excellent Online Spectra Database. Click here to viewMass Spectra Online Database

1Search methane molecule, CH4 Video on mass spectrometerMass/charge m/z Relative abundance Isotopic peak M+ + 1 Molecular ion peak, M+ 2Fragmentation pattern CH4 3Mass Spectrum CH4

Video how MS works

Mg - 3 Isotopes

26 Mg - 11.3% - m/z highest deflect LEAST25 Mg - 10.0% 24 Mg 78.6% - m/z lowest deflect MOST Relative Isotopic Mass:= (24Mg x % Ab) + (25Mg x % Ab) + (26Mg x % Ab)= (24 x 78.6/100) + (25 x 10.0/100) + (26 x 11.3/100) = 24.30 Mass spectrometry to determine Relative Isotopic Mass

Deflect MOSTDeflect LEAST

Pb - 4 Isotopes

208Pb 52% - m/z highest deflect LEAST207Pb - 22% 206Pb - 24% 204Pb 2% - m/z lowest deflect MOST Relative Isotopic Mass= (204Pb x % Ab) + (206Pb x % Ab) + (207Pb x % Ab) + (208Pb x % Ab)= (204 x 2/100) + (206 x 24/100) + (207 x 22/100) + (208 x 52/100) = 207.20Deflect MOSTDeflect LEAST24 Mg 26 Mg 204Pb208Pb

CI - 2 Isotopes37 CI 24.5% - m/z highest deflect LEAST 35 CI 75.5% - m/z lowest deflect MOST Relative Isotopic Mass:= (35CI x % Ab) + (37CI x % Ab)= (35 x 75.5/100) + (37 x 24.5/100) = 35.5

Deflect MOSTDeflect LEAST

Br - 2 Isotopes81Br 49.3% - m/z highest deflect LEAST79Br 50.6% - m/z lowest deflect MOSTDeflect MOSTDeflect LEAST35CI37CI

Relative Isotopic Mass:= (79Br x % Ab) + (81Br x % Ab)= (79 x 50.6/100) + (81 x 49.3/100) = 79.979Br81Br

Mass spectrometry to determine Relative Isotopic Mass35 CI 37 CI 79Br81Br

H - 3 Isotopes3H trace amt 2H 0.015% - m/z highest deflect LEAST 1H 99.9% - m/z lowest deflect MOST Relative Isotopic Mass:= (1H x % Ab) + (2H x % Ab)= (1 x 99.9/100) + (2 x 0.015/100) = 1.007

Deflect MOSTDeflect LEAST

C - 3 Isotopes14C- trace amt13C 1.1% - m/z highest deflect LEAST12C 98.9% - m/z lowest deflect MOSTDeflect MOSTDeflect LEAST1H2H Relative Isotopic Mass:= (12C x % Ab) + (813Cx % Ab)= (12 x 98.9/100) + (13 x 1.1/100) = 12.0112C13C3H

14C

Mass spectrometry to determine Relative Isotopic Mass1H2H12C13C

Ionization and Fragmentation Ionization forming M+CH3CH2CH2 : CH3 + e CH3CH2CH2+.CH3 + 2e

Fragmentation of M+ producing 43CH3CH2CH2+CH3 CH3CH2CH2+ + CH3

Fragmentation of M+ producing 15CH3CH2CH2+CH3 CH3CH2CH2 + +CH3

Ionization and Fragmentation Process- CH3CH2CH2CH3 Ionization Process - CH3CH2CH2CH3 Bombard by electron form cation Molecular ion, M+ = 58 (CH3CH2CH2CH3)+ = 58Fragmentation Process CH3CH2CH2CH3 Molecular ion, M+ undergo fragmentation Cation and Radical form Cation - Detected Radical Not detected (No charged) H H CH3CH2CH2 C:H + e CH3CH2CH2 C+.H + 2e H H Ionization forming M+CH3CH2:CH2CH3 + e CH3CH2+CH2CH3 + 2e

Fragmentation of M+ producing 29CH3CH2+CH2CH3 CH3CH2+ + .CH2CH3

Ionization M+, m/z = 58CH3CH2CH2CH3 + e CH3CH2CH2CH3+ + 2eIonization and Fragmentation of M+ Form - m/z = 58, 43 and 15 m/z = 58m/z = 43m/z = 15Ionization and Fragmentation of M+ Form- m/z = 58 and 29m/z = 58m/z = 58m/z = 29Unpair electronPositively charged

Will ACCELARATEDNOT movecationradical

CH3CH2CH2CH3CH3CH2CH2CH3+- 58 - m/z highest deflect LEAST CH3CH2CH2+ 43 CH3CH2+ 29 CH3+ 15 - m/z lowest deflect MOSTIonization/ Fragmentation pattern CH3CH2CH2CH3

Deflect MOSTDeflect LEASTCH3CH2CH2CH3+CH3CH2CH2+Fragmentation ionizationCH3+Ionization and Fragmentation ProcessFragmentation Ionization CH3CH2CH2CH3 CH3CH2CH2CH3 + e CH3CH2CH2CH3+ + 2e 58 or CH3CH2:CH2CH3 + e CH3CH2+CH2CH3 + 2e 58Mass spectrum CH3CH2CH2CH3 IonizationCH3CH2CH2CH3 CH3CH2+

Fragmentation of M+CH3CH2CH2+CH3 CH3CH2CH2+ - 43

CH3CH2+CH2CH3 CH3CH2+ 29 CH3CH2CH2+CH3 +CH3 - 15

CH3CH2CH2CH3+- 58CH3CH2CH2+ 43 CH3CH2+ 29 CH3+ 15

CH3+ CH3CH2CH2CH3+

CH3CH2CH2OHCH3CH2CH2OH+- 60 - m/z highest deflect LEAST CH2CH2OH+ 45CH2OH+ - 31CH3CH2+ 29 CH3+ 15 - m/z lowest deflect MOSTIonization/ Fragmentation pattern CH3CH2CH2OH

Deflect MOSTDeflect LEASTCH3CH2CH2OH+Fragmentation ionizationCH3 +Fragmentation Ionization CH3CH2CH2OHCH3CH2CH2OH + e CH3CH2CH2OH+ + 2e 60 orCH3CH2CH2OH + e CH3CH2+. CH2OH + 2e 60Mass spectrum CH3CH2CH2OH CH3CH2CH2OH CH3CH2+ Fragmentation of M+CH3+.CH2CH2OH +CH2CH2OH - 45

CH3CH2+CH2OH +CH2OH 31 CH3CH2+CH2OH CH3CH2+ 29

CH3+.CH2CH2OH +CH3 - 15

CH2CH2OH+CH2OH+

1560CH3CH2CH2OH+- 60 CH2CH2OH+ 45CH2OH+ - 31CH3CH2+ 29 CH3+ 15

1560

Ionization and Fragmentation ProcessIonizationCH3+ CH3CH2CH2OH+

CH3CH(CH3)CH2CH3+- 72 - m/z highest deflect LEAST CH3CH(CH3)CH2+ 57CH3CH(CH3)+ - 43CH3CH2+ 29 CH3+ 15 - m/z lowest deflect MOSTIonization/ Fragmentation pattern CH3CH(CH3)CH2CH3

Deflect MOSTDeflect LEASTCH3CH(CH3)CH2CH3+Fragmentation IonizationCH3+Fragmentation Ionization of CH3CH(CH3)CH2CH3 CH3CH(CH3)CH2CH3 + e CH3CH(CH3)CH2CH3 + + 2e 72 orCH3CH(CH3)CH2CH3 + e CH3CH(CH3)CH2+.CH3 + 2e 72 orCH3CH(CH3)CH2CH3 + e CH3CH(CH3)+.CH2CH3 + 2e 72Mass spectrum CH3CH(CH3)CH2CH3 IonizationCH3CH(CH3)CH2CH3 Fragmentation of M+CH3CH(CH3)CH2+ - 57CH3CH(CH3)+ 43 CH3CH2+ 29CH3+ - 15CH3CH(CH3)+15CH3CH(CH3)CH2+CH3CH(CH3)CH2CH3+CH3CH2+

CH3CH(CH3)CH2CH3+- 72CH3CH(CH3)CH2+ 57CH3CH(CH3)+ - 43CH3CH2+ 29 CH3+ 15

Ionization and Fragmentation ProcessCH3+ CH3CH(CH3)CH2CH3+

(C(CH3)4)+ - 72 - m/z highest deflect LEAST (C(CH3)3)+ 57(C(CH3)2)+ - 42(C(CH3))+ 27CH3+ 15 - m/z lowest - deflect MOSTIonization/ Fragmentation pattern C(CH3)4

Deflect MOSTDeflect LEASTFragmentation IonizationFragmentation Ionization of C(CH3)4 C(CH3)4 + e (C(CH3)4)+ + 2e 72Mass spectrum C(CH3)4 IonizationC(CH3)4 (C(CH3)3)+ (C(CH3)4) (C(CH3)2)+ (C(CH3))+ (C(CH3)4)+ - 72(C(CH3)3)+ 57(C(CH3)2)+ - 42(C(CH3))+ 27CH3+ 15 Fragmentation M+(C(CH3)3)+ 57(C(CH3)2)+ - 42(C(CH3))+ 27CH3+ 15

Ionization and Fragmentation ProcessCH3+ (C(CH3)4)+ CH3 CH3-C-CH3 CH3

Ionization/ Fragmentation pattern CH3(CH2)8CH3

Fragmentation IonizationFragmentation Ionization of CH3(CH2)8CH3CH3(CH2)8CH3 + e CH3(CH2)8CH3+ + 2e 142Mass spectrum CH3(CH2)8CH3IonizationCH3(CH2)8CH3CH3(CH2)8CH3+CH3(CH2)8CH3+ = 142 - m/z highest deflect LEAST CH3(CH2)7CH2+ = 127 CH3(CH2)6CH2+ = 113CH3(CH2)5CH2+ = 99CH3(CH2)4CH2+ = 85CH3(CH2)3CH3+ = 71CH3(CH2)2CH2+ = 57CH3CH2CH2+ = 43CH3CH2+ = 29CH3+ = 15 m/z lowest deflect MOST

Loss of methylene gp, CH2 = 14CH3(CH2)8CH3CH3(CH2)7CH2+ = 127 CH3(CH2)6CH2+ = 113CH3(CH2)5CH2+ = 99CH3(CH2)4CH2+ = 85CH3(CH2)3CH3+ = 71CH3(CH2)2CH2+ = 57CH3CH2CH2+ = 43CH3CH2+ = 29CH3+ = 15

Deflect LEAST

CH3+Deflect MOSTCH3(CH2)8CH3+Ionization and Fragmentation Process 15

Ionization/ Fragmentation pattern CH3(CH2)8CH3

Fragmentation IonizationFragmentation Ionization of C6H5CH2OHC6H5CH2OH + e C6H5CH2OH+ + 2e 108Mass spectrum CH3(CH2)8CH3IonizationC6H5CH2OH+ = 108 - m/z highest deflect LEAST C6H5CH2+ = 91C6H5+ = 77CH2OH+ = 31OH+ = 17 m/z lowest deflect MOST

C6H5CH2OHC6H5CH2OH+C6H5CH2OH

C6H5CH2OH+C6H5CH2+ = 91C6H5+ = 77CH2OH+ = 31OH+ = 17 C6H5CH2OH+ = 108C6H5CH2+ = 91C6H5+ = 77CH2OH+ = 31OH+ = 17

OH+Deflect MOSTDeflect LEASTIonization and Fragmentation Process

Isomers, Propan-1-ol vs Propan-2-ol Peak 45 is higher Loss of methyl radical at both sides produce (CH3CH(OH))+ No m/z= 29 peak detected No CH2CH3 found ! Fragmentation peak(M - 15)+ = 45 -> (CH2CH2OH)+

(M - 29)+ = 31 -> (CH2OH)+

(M - 31)+ = 29 -> (CH3CH2)+

(M - 45)+ = 15 -> (CH3)+ Isomers of C3H8OH Fragmentation peaks (M - 15)+ = 45 -> (CH3CH(OH))+

(M - 17)+ = 43 -> (CH3CHCH3)+

(M - 33)+ = 27 -> (CH3C)+ VsLoss of CH3Loss of CH3CH2Loss of CH2OHLoss of CH2CH2OHLoss CH3 OH OH CH3 C+CH3 CH3 C+ + CH3 H H

m/z= 45

CH3CH2CH2OH OH |CH3CHCH3Loss OHLoss OH, CH3, H Peak 29 and 31 are found Inductive effect of OH cause splitting of CH3CH2-|-CH2OH m/z = 29 peak detected CH2CH3 presentCH3CH2 + CH2OH CH3CH2 + + CH2OH

m/z= 29CH3CH2 + CH2OH CH3CH2 + +CH2OH

m/z= 31Propan-1-olPropan-2-ol15Vs

Molecular Ion, M+ = 60 -> CH3CH2CH2OH+ Molecular Ion, M+ = 60 -> CH3CH(OH)CH3+

Isomers, 2 methylbutane vs 2, 2 dimethylpropane CH3 CH3CHCH2CH3 CH3 |CH3C-CH3 | CH3

Peak 29 absent No CH3CH2Peak 57 is higher Loss of methyl radical produce tertiary carbocation Tertiary carbocation More stable Fragmentation peaks(M - 15)+ = 57 -> CH3CH(CH3)CH2+

(M - 29)+ = 43 -> CH3CH(CH3)+

(M - 43)+ = 29 -> CH3CH2+

(M - 57)+ = 15 -> CH3+ Isomers of C5H12 Fragmentation peaks (M - 15)+ = 57 -> C(CH3)3+

(M - 30)+ = 42 -> C(CH3)2+

(M - 45)+ = 27 -> CH3C+

(M - 57)+ = 15 -> CH3+ VsLoss of CH3Loss of CH3CH2Loss of CH3CH(CH3)Loss of CH3CH(CH3)CH2Loss of CH3Loss of TWO CH3Loss of THREE CH3 CH3 CH3C+CH3 CH3

m/z= 57 CH3 CH3 C+ + CH3 CH32 methylbutane 2, 2 dimethylpropaneLoss of C(CH3)3VsPeak 29 absent CH3CH2 presentMolecular Ion, M+ = 72 -> CH3CH(CH3)CH2CH3+ Molecular Ion, M+ = 72 -> C(CH3)4+

Normal Vs High Resolution Mass spectrometer Normal Mass Spectrometer Molecular formula by adding all RAM RMM for molecule = Sum of all RAM RMM O2 = 16 + 16 = 32 RMM N2H4 = (14 x 2) + (1 x 4) = 32 RMM CH3OH = (12 + 3 + 16 + 1) = 32 Molecular ion peak - O2, N2H4, CH3OH - SAME = 32RAM, O = 16RAM, N = 14RAM, H = 1RAM, C = 12 High Resolution Mass SpectrometerMeasure RMM to 4/5 decimal places Molecular formula by adding all RAM RMM for molecule = Sum of all RAM RMM O2 = 15.9949 + 15.9949 = 31.9898 RMM N2H4 = (14.0031 x 2) + (1.0078 x 4) = 32.0375 RMM CH3OH = (12.0000 )+ (3 x 1.0078) + 15.9949 = 32.0262 Molecular ion peak- O2, N2H4, CH3OH is the NOT the sameRAM, O = 15.9949RAM, N = 14.0031RAM, H = 1.0078RAM, C = 12.0000

VsVsO2, N2H4, CH3OHSame 32O2N2H4 CH3OHdifferent

http://www.absciex.com/

Video how MS works High resolution Mass spectrum

37CI+35CI+CI2 molecule37CI-37CI - 74 - m/z highest deflect LEAST 35CI-37CI 72 35CI-35CI 70 37CI 37 35CI 35 - m/z lowest deflect MOSTIonization/ Fragmentation pattern CI2

Deflect MOST Deflect LEAST35CI-35CI+35CI+35CI-37CI+37CI-37CI+Fragmentation form atomIonization37CI+

37CI-37CI+Fragmentation Fragmentation of CI2+ into CI+CI+.CI [35CI+ + 35CI] + 2e 35

CI+.CI [37CI+ + 37CI] + 2e 37

Ionization of CI2 to CI2+CI:CI + e- [35CI+.35CI] + 2e 70CI:CI + e- [35CI+.37CI] + 2e 72CI:CI + e- [37CI+.37CI] + 2e 74

m/z = 37m/z = 35

Ratio (35CI : 37CI) - 3:1

Mass spectrum CI2 / CI atom

Ratio (35CI35CI: 35CI37CI: 37CI37CI) - 9:6:1IonizationCI2 molecule37CI-37CI - 7435CI-37CI 72 35CI-35CI 70 37CI 37 35CI 35Ionization and Fragmentation Process

Br2 molecule81Br-81Br - 162 - m/z highest deflect LEAST 79Br-81Br 160 79Br-79Br 158 81Br 81 79Br 79 - m/z lowest deflect MOST

Deflect MOSTDeflect LEAST79Br-79Br+79Br+79Br-81Br+81Br-81Br+Fragmentation form atomIonization81Br+79Br+81Br-81Br+Fragmentation Fragmentation of Br2+ to Br+Br+.Br [81Br+ + 81Br] 81

Br+.Br [79Br+ + 79Br] 79

Ionization of Br2 to Br2+Br:Br + e- [81Br+.81Br] + 2e 162Br:Br + e- [79Br+.81Br] + 2e 160Br:Br + e- [79Br+.79Br] + 2e 158

m/z = 79m/z = 81Ratio (79Br : 81Br) - 1:1Mass spectrum Br2 / Br atomsRatio (79Br79Br: 79Br81Br: 81Br81Br) 1:2:1IonizationBr2 molecule81Br-81Br - 162 79Br-81Br 160 79Br-79Br 158 81Br 81 79Br 79

Ionization/ Fragmentation pattern Br2 Ionization and Fragmentation Process

Ionization/ Fragmentation pattern CH3CH(CI)CH3

Fragmentation IonizationIonization Ionization CH3CH(CI)CH3CH3CH(CI)CH3+ e CH3CH(CI)CH3+ + 2e 78/80Presence isotope 35CI and 37CICH3CH(37CI)CH3+ = 80 - m/z highest deflect LEAST CH3CH(35CI)CH3+ = 78 CH3CH(37CI)+ = 65CH3CH(35CI)+ = 63CH3CHCH3+ = 43CH3C + = 27 - m/z lowest deflect MOST

CH3CH(37CI)+ = 65CH3CH(35CI)+ = 63CH3CHCH3+ = 43CH3C + = 27CH3CH(CI)CH3CH3CH(CI)CH3+

CH3CH(CI)CH3+

Isotopic peak (M+)= 78 Isotopic peak (M++2) = 80CH3CH(35CI)CH3CH3CH(37CI)CH3

Isotopic peak 63 Isotopic peak 65 CH3CH(35CI)+CH3CH(37CI)+CH3CH(CI)CH3FragmentationCH3C+Deflect MOSTDeflect LEAST

Presence M+ and (M++ 2) peakPresence of IsotopesIonization and Fragmentation Process

CH3CH2CH279Br CH3CH2CH281BrCH2CH279BrCH2CH281BrIonization/ Fragmentation pattern CH3CH2CH3Br

Fragmentation IonizationIonization Ionization CH3CH2CH2BrCH3CH2CH2Br + e CH3CH2CH2Br+ + 2e 122/124Presence isotope 79Br and 81BrCH3CH2CH281Br+ = 124 - m/z highest deflect LEAST CH3CH2CH279Br + = 122CH2CH281Br+ = 109CH2CH279Br+ = 107CH281Br+ = 95CH279Br+ = 93CH3CH2CH2+ = 43CH3C + = 27 - m/z lowest deflect MOST

Isotopic peak (M+) = 122Isotopic peak (M++2) = 124

Isotopic peak 107Isotopic peak 109FragmentationCH3C+Deflect MOSTDeflect LEAST

CH3CH2CH2Br CH3CH2CH2Br+ CH3CH2CH3Br CH3CH2CH2Br+CH2CH281Br+ = 109CH2CH279Br+ = 107CH281Br+ = 95CH279Br+ = 93CH3CH2CH2+ = 43CH3C + = 27

CH3C+Deflect LEAST CH3CH2CH2Br+

Presence of M+ and (M++ 2) peak

Presence of IsotopesDeflect MOSTIonization and Fragmentation Process

TI IB Questions on Mass SpectrometerMass spectrometer used to investigate isotopic composition of elements. Thallium has two isotopes.

1) State symbol of two singly charged ions form.

2) State which ion will follow path marked X on diagram.

lighter -> DEFLECTED MORE

3) Doubly charged ions form. Suggest reason whether they would be deflected less or more than ions at X and Y. DEFLECTED MORE. Cause deflection depends on m/z ratio. Low Mass + High charge -> m/z ratio is low -> deflected more.Naturally occuring boron has 2 isotopes. RAM boron is 10.81.

% abundance x% (100 x)%Determine percentage abundance of these isotopes.Answer: Let % abundance be x.

1

TI TI 2032058181X = B 10 B 11 Relative Isotopic Mass:= (Mass 10B x % Ab) + (Mass 11B x % Ab) = (10 x x/100) + (11 x (100 x)/100) = 10.81X = 19% TI+ 81203 TI+ 20581

TI+ 20381

IB Questions on Mass SpectrometerGermanium is analysed in mass spec. The first and last processes are vaporization and detection.

1) State the names of other 3 processes in order in which they occur Answer: Ionization -> Acceleration -> Deflection 2) For each of processes named in a (i), outline how process occur

Ionization -> Sample bombarded with high energy/high speed electrons Acceleration -> Cations (+ve charged ions) accelerated by an electric field Deflection -> Cations deflected by a magnetic field

3) Germanium found to have following composition

Define relative atomic mass. Average / weighted masses of all isotopes of an element.

ii) Calculate RAM, giving answer to two decimal places.

2

Relative Isotopic Mass= (Mass 70Ge x % Ab) + (Mass 72Ge x % Ab) + (Mass 74Ge x % Ab) + (Mass 76Ge x % Ab)= (70 x 22.60/100) + (72 x 25.45/100) + (74 x 36.73/100) + (76 x 15.22/100) = 72.89

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IB Questions on Mass SpectrometerShows a mass spectrometer.Identify the parts labelled A, B and C.

State and explain which one will undergo greatest deflection.

Answer : Greatest deflection -> lowest mass + highest charged -> m/z -> lowest

3) Mass spectrum shown below:

i) Explain why there is more than one peak. Existence of isotopes

ii) Calculate RAM.

3

Relative Isotopic Mass= (Mass 24Y x % Ab) + (Mass 25Y x % Ab) + (Mass 26Yx % Ab)= (24 x 79/100) + (25 x 10/100) + (26 x 11/100) = 24.32

electron gunionisation chamberionizer Electric fieldCharged platesPotential differenceMagnetic fieldMagnetElectromagnet

greatest deflection low mass, high chargedsmallest deflection high mass, low charged

ACB Li+ Li2+ 76

30

IB Questions on Mass SpectrometerVaporized magnesium is introduced into mass spec. One of the ions that reaches detector shown below.

Identify number of protons, neutron and electrons Answer : 12 protons, 13 neutrons, 11 electrons

2) State how ion is accelerated in mass spectrometer. Using a strong electric field/strong opposite charged plate/potential difference

3) The ion is also detected by changing the magnetic field. Deduce and explain by reference to

m/z values of these two ions of magnesium, which of the ions and is detected using a stronger magnetic field.

Answer: - due to lower charge -> m/z is higher -> deflected less -> needs a stronger magnetic field to deflect.

4

Cations (+ve) accelerated by (-ve) plates

2512

25Mg 2+

smallest deflection high mass, low chargedStrong magnet/magnetic field to deflect it to bottom Mg + 25Mg 2+25Mg +25Mg +25Mg +

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Rubidium contains two stable isotopes. RAM for rubidium is 85.47

Calculate % of each isotope in rubidium. Answer : Let % abundance be x %.

% Abundance x% (100 x)%

76.5% 23.5%

2) Vaporized sample is ionized and accelerated. How the use of magnetic field and detector enables percentage of two isotopes to be determined.

5

8587 Relative Isotopic Mass:= (Mass 85Rb x % Ab) + (Mass 87Rb x % Ab) = (85 x x/100) + (87 x (100 x)/100) = 85.47X = 76.5% Rb

Detector Convert abundance M+ ions to current. M+ ions neutralize by electrons (more e needed - higher current higher intensity of peak)Ratio of intensity peaks show ratio of ions in sampleRatio of height of peaks due to 85Rb : 87Rb > 76.5 : 23.5 Magnetic field/Deflector M+ ion deflected by magnetic field

- lighter -> deflected more

- heavier -> deflected less

IB Questions on Mass SpectrometerRb Rb 85 Rb 87 Rb 85 Rb 87 Rb 85 Rb 87 Rb

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Acknowledgements

Thanks to source of pictures and video used in this presentationhttp://serc.carleton.edu/research_education/geochemsheets/techniques/gassourcemassspec.htmlhttp://www.mhhe.com/physsci/chemistry/carey/student/olc/ch13ms.htmlhttp://science.howstuffworks.com/mass-spectrometry3.htm

Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/

Prepared by Lawrence Kok

Check out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com