The document discusses index hydrogen deficiency (IHD), which is a measure of unsaturation in molecules. IHD is calculated based on the number of hydrogen atoms fewer than would be present in a saturated molecule with the same number of carbon atoms. The document provides examples of calculating IHD for various molecules containing double bonds, rings, and heteroatoms like nitrogen. It also describes how mass spectrometry can be used to determine IHD and identify molecular structures based on their fragmentation patterns.

1. 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 H
Hexane
C6H14 IHD = 0
Hex-2-ene
C6H12 IHD = 1
Hex-3-ene
C6H12 IHD = 1
Cyclohexane
C6H12 IHD = 1
How many double bonds/rings present
Any double/triple bond/cyclic - number hydrogen atoms decrease
How many H2 need to convert molecule to saturated/noncyclic
Saturatedhydrocarbon = CnH2n+2
Saturated
IDH = 0
Unsaturated
(1 π bond)
2 H deficiency
IHD = 1
H H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
Unsaturated
(2 π bond)
4 H deficiency
IHD = 2
Unsaturated
(1 ring)
2 H deficiency
IHD = 1
Unsaturated
(3 π bond) + 1 ring
8 H deficiency
IHD = 4
IHD = 1
1 π bond or 1 ring structure
Unsaturated
(2 π bond) + 1 ring
6 H deficiency
IHD = 3
Unsaturated
(4 π bond) + 1 ring
10 H deficiency
IHD = 5
IHD = 2
2 π bond / 1 π bond + 1 ring
IHD = 3
3 π bond / 2 π bond + 1 ring / 1 π bond+ 2 ring
Unsaturated
(4 π bond) + 1 ring
10 H deficiency
IHD = 5
Unsaturated
(6 π bond) + 2 ring
16 H deficiency
IHD = 8
Click here IHD (Khan Academy)

2.  
2
22 yx
IHD


H H H H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C - C – C – C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H H H H H H
Hexane
C6H14 IHD = 0
Hex-2-ene
C6H12 IHD = 1
Hex-3-ene
C6H12 IHD = 1
Cyclohexane
C6H12 IHD = 1
 
2
22 rsyx
IHD


How many double bonds/rings present
Any double/triple bond/cyclic - number hydrogen atoms decrease
How many H2 need to convert molecule to saturated/noncyclic
IHD = 1
1 π bond or 1 ring structure
IHD = 2
2 π bond / 1 π bond + 1 ring
IHD = 3
3 π bond / 2 π bond + 1 ring / 1 π bond+ 2 ring
Molecule with C and H Molecule with N, O, S or Halogen
yx HC srqyx XNOHC
C6H12 C2H2
 
1
2
)12262(
2
22





IHD
IHD
yx
IHD
or
 
2
2
)2222(
2
22





IHD
IHD
yx
IHD
(1 π bond / 1 ring) (2 π bond)
C2H3CI C5H7N
 
1
2
)13222(
2
22





IHD
IHD
syx
IHD
 
3
2
)17252(
2
22





IHD
IHD
ryx
IHD
H - C = C - CI
‫׀‬ ‫׀‬
H H
(1 π bond) (3 π bond / 2 π 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
Index Hydrogen Deficiency (IHD) = Degree unsaturation Saturatedhydrocarbon = CnH2n+2

3. Molecule Index H2 Deficiency
C2H2 2
Oxygen and Sulfur - No effect on IHD
Halogen - like H – CHCI3 = CH4 , C2H5CI = C2H6
Nitrogen – add one to C and one to H
- CH5N same IHD as C2H6
Index Hydrogen Deficiency (IHD) = Degree unsaturation
How many double bonds/rings present
Any double/triple bond/cyclic - number hydrogen atoms decrease
Molecule with N, O, S or Halogen
srqyx XNOHC
 
2
22 rsyx
IHD

 Click here IHD video
  1
2
)4222(
2
22





yx
IHD
  2
2
)2222(
2
22





yx
IHD
  1
2
)4222(
2
22





yx
IHD
  0
2
)15222(
2
22





syx
IHD
  4
2
)6262(
2
22





yx
IHD
Molecule Index H2 Deficiency
C2H4 1
Molecule Index H2 Deficiency
C2H4O 1
Molecule Index H2 Deficiency
C2H5CI 0
Molecule Index H2 Deficiency
C6H6 4
Molecule Index H2 Deficiency
C7H6O2 5
  5
2
)6272(
2
22





yx
IHD
Molecule Index H2 Deficiency
C7H9N2CI3 3
  1
2
)19242(
2
22





ryx
IHD
Molecule Index H2 Deficiency
C4H9N 1
  3
2
)239272(
2
22





rsyx
IHD
Molecule Index H2 Deficiency
C6H9NOCI2 2
  2
2
)129262(
2
22





rsyx
IHD
Molecule Index H2 Deficiency
C4H8CIF 0
  0
2
)28242(
2
22





syx
IHD
Click here IHD (Khan Academy)
Molecule Index H2 Deficiency
C6H12O6 1
  1
2
)12262(
2
22





yx
IHD
Halogen

4. Click here spectroscopy database (NIST)
Weighted average calculationRAM calculationVideo on IsotopesVideo on weighted average
Relative Atomic Mass
Weighted average mass- due to presence of isotopes
RelativeIsotopic 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 = 12.01 Relative Abundance
13
Why RAM is not a whole number?
Relative IsotopicMass:
= (Mass 12
C x % Ab) + (Mass 13
C x % Ab)
= (12 x 98.9/100)+ (13 x 1.07/100)= 12.01
Video on Isotopes
12
Isotopes are present
CCC12.01
98.9% 1.07%
Click here spectroscopy database (Ohio State)

5. 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 24
Mg x % Ab) + (Mass 25
Mg x % Ab) + (Mass 26
Mg x % Ab)
= (24 x 78.6/100)+ (25 x 10.0/100) + (26 x 11.3/100) =24.30
Relative Abundance % Abundance
Pb - 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) = 207.20
Convert relative abundance to % abundance
Convert relative abundance to % abundance
Relative Abundance % Abundance
RelativeIsotopic Mass
24 25 2624 25 26 MgMg

6. Mass Spectrometer
Uses mass spectrometer
Presence of isotopes
and its abundance
Relative atomic mass
of an element
Relative Molecular mass
of a molecule
Structure of organic
compound
Distinguish bet
structural isomers
CH3CH2CH2OH OH
|
CH3CHCH3
CH3
|
CH3C-CH3
|
CH3
CO2
structural
formula
Organic structure
determination
24 25 26Mg
Mg

7. Detail notes from chem msuClick here notes from chemguide
Mass Spectrometer
Parts of Mass Spectrometer
Sample injection
VaporizationChamber
• Sample heat to
vapour state
IonizationChamber
• Molecule bombard with
electron form positive ion
AcceleratorChamber
• M+ ion acceleratedby Electric field
Deflector
• M+ ion deflected by magnetic field
Detector
• Convert amt M+ ion to current.
• M+ ion neutralize by electron (more
 e need -  higher current – 
higher intensity of peak)
• Intensity of peak show -relative
abundanceof 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 Detector321 54
2
1
3 4
5

8. Click here for simulation
Mass Spectrometer
Parts of Mass Spectrometer
Vaporization Ionization Accelerator Deflector Detector321 54
Vaporization
Injection/ vaporization of sample
liquid state  gaseous
Ionization
Form cation, M+
Acceleration
M+ ion accelerate
by Electric field
Deflection
M+ ion deflect
by 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 ↑
37
CI+
35
CI+
35
CI2+
2
3 4
1
5 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

9. Video Mass spectrometerVideo Ionization/fragmentation Video how MS works
Excellent Online Spectra Database.Click here to view
Mass Spectra Online Database
1 Search methane molecule, CH4
Video on mass spectrometer
Mass/charge m/z
Relative
abundance
Isotopic peak M+ + 1Molecular ion peak, M+
2 Fragmentation pattern CH4 3 Mass Spectrum CH4
Video how MS works

10. Mg - 3 Isotopes
26 Mg - 11.3% - m/z highest – deflect LEAST
25 Mg - 10.0%
24 Mg – 78.6% - m/z lowest – deflect MOST
Relative Isotopic Mass:
= (24
Mg x % Ab) + (25
Mg x % Ab) + (26
Mg 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
MOST
Deflect
LEAST
Pb - 4 Isotopes
208Pb – 52% - m/z highest – deflect LEAST
207Pb - 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) = 207.20
Deflect
MOST
Deflect
LEAST
24 Mg 26 Mg
204Pb 208Pb

11. CI - 2 Isotopes
37 CI – 24.5% - m/z highest – deflect LEAST
35 CI – 75.5% - m/z lowest – deflect MOST
Relative Isotopic Mass:
= (35
CI x % Ab) + (37
CI x % Ab)
= (35 x 75.5/100) + (37 x 24.5/100) = 35.5
Deflect
MOST
Deflect
LEAST
Br - 2 Isotopes
81Br – 49.3% - m/z highest – deflect LEAST
79Br – 50.6% - m/z lowest – deflect MOST
Deflect
MOST
Deflect
LEAST
35CI 37CI
Relative Isotopic Mass:
= (79
Br x % Ab) + (81
Br x % Ab)
= (79 x 50.6/100) + (81 x 49.3/100) = 79.9
79Br 81Br
Mass spectrometry to determine Relative Isotopic Mass
35 CI 37 CI
79Br 81Br

12. H - 3 Isotopes
3H – trace amt
2H – 0.015% - m/z highest – deflect LEAST
1H – 99.9% - m/z lowest – deflect MOST
Relative Isotopic Mass:
= (1
H x % Ab) + (2
H x % Ab)
= (1 x 99.9/100) + (2 x 0.015/100) = 1.007
Deflect
MOST
Deflect
LEAST
C - 3 Isotopes
14C- trace amt
13C – 1.1% - m/z highest – deflect LEAST
12C – 98.9% - m/z lowest – deflect MOST
Deflect
MOST
Deflect
LEAST
1H 2H
Relative Isotopic Mass:
= (12
C x % Ab) + (813
Cx % Ab)
= (12 x 98.9/100) + (13 x 1.1/100) = 12.01
12C 13C
3H
14C
Mass spectrometry to determine Relative Isotopic Mass
1H 2H
12C 13C

13. Ionization and Fragmentation
Ionization forming M+
CH3CH2CH2 : CH3 + e → CH3CH2CH2
+
.CH3 + 2e
• Fragmentation of M+
producing 43
CH3CH2CH2
+
·CH3 → CH3CH2CH2
+
+ ·CH3
• Fragmentation of M+
producing 15
CH3CH2CH2
+
·CH3 → CH3CH2CH2· + +
CH3
Ionization and Fragmentation Process- CH3CH2CH2CH3
Ionization Process - CH3CH2CH2CH3
• Bombard by electron form cation
• Molecular ion, M+
= 58
• (CH3CH2CH2CH3)+
= 58
Fragmentation Process CH3CH2CH2CH3
• Molecular ion, M+ undergo fragmentation
• Cation and Radical form
• Cation - Detected
• Radical –Not detected (No charged)
H H
‫׀‬ ‫׀‬
CH3CH2CH2 C:H + e → CH3CH2CH2C+.H + 2e
‫׀‬ ‫׀‬
H H
Ionization forming M+
CH3CH2:CH2CH3 + e → CH3CH2
+·CH2CH3 + 2e
• Fragmentation of M+
producing29
CH3CH2
+·CH2CH3 → CH3CH2
+
+ .CH2CH3
Ionization M+
, m/z = 58
CH3CH2CH2CH3 + e → CH3CH2CH2CH3
+
+ 2e
Ionization and Fragmentation of M+
• Form - m/z = 58, 43 and 15
m/z = 58
m/z = 43
m/z = 15
Ionization and Fragmentation of M+
• Form- m/z = 58 and 29
m/z = 58
m/z = 58
m/z = 29
Unpair electronPositively charged
Will ACCELARATED NOT move
cation radical

14. CH3CH2CH2CH3
CH3CH2CH2CH3
+- 58 - m/z highest –deflect LEAST
CH3CH2CH2
+ – 43
CH3CH2
+ – 29
CH3
+ –15 - m/z lowest– deflect MOST
Ionization/ Fragmentationpattern CH3CH2CH2CH3
Deflect
MOST
Deflect
LEAST
CH3CH2CH2CH3
+
CH3CH2CH2
+
ionization
CH3
+
Ionization and FragmentationProcess
Fragmentation
Ionization CH3CH2CH2CH3
CH3CH2CH2CH3 + e → CH3CH2CH2CH3
+
+ 2e → 58
or
CH3CH2:CH2CH3 + e → CH3CH2
+·CH2CH3 + 2e → 58
Mass spectrum CH3CH2CH2CH3IonizationCH3CH2CH2CH3
CH3CH2
+
Fragmentation of M+
CH3CH2CH2
+
·CH3 → CH3CH2CH2
+
- 43
CH3CH2
+·CH2CH3 → CH3CH2
+
– 29
CH3CH2CH2
+
·CH3 → +CH3 - 15
CH3CH2CH2CH3
+- 58
CH3CH2CH2
+ – 43
CH3CH2
+ – 29
CH3
+ – 15
CH3
+ CH3CH2CH2CH3
+

15. CH3CH2CH2OH
CH3CH2CH2OH+- 60 - m/z highest –deflect LEAST
CH2CH2OH+ – 45
CH2OH+ - 31
CH3CH2
+ – 29
CH3
+ –15 - m/z lowest– deflect MOST
Ionization/ Fragmentation pattern CH3CH2CH2OH
Deflect MOST Deflect LEAST
CH3CH2CH2OH+
ionization
CH3
+
Fragmentation
Ionization CH3CH2CH2OH
CH3CH2CH2OH + e → CH3CH2CH2OH+
+ 2e → 60
or
CH3CH2CH2OH + e → CH3CH2
+. CH2OH + 2e → 60
Mass spectrum CH3CH2CH2OHCH3CH2CH2OH
CH3CH2
+
Fragmentation of M+
CH3
+.CH2CH2OH → +CH2CH2OH - 45
CH3CH2
+·CH2OH → +CH2OH – 31
CH3CH2
+·CH2OH → CH3CH2
+ – 29
CH3
+.CH2CH2OH → +CH3 - 15
CH2CH2OH+ CH2OH+
15
60
CH3CH2CH2OH+- 60
CH2CH2OH+ – 45
CH2OH+ - 31
CH3CH2
+ – 29
CH3
+ – 15
15 60
Ionization and FragmentationProcess
Ionization
CH3
+ CH3CH2CH2OH+

16. CH3CH(CH3)CH2CH3
+- 72 - m/z highest –deflect LEAST
CH3CH(CH3)CH2
+ – 57
CH3CH(CH3)+ - 43
CH3CH2
+ – 29
CH3
+ –15 - m/z lowest– deflect MOST
Ionization/ Fragmentation pattern CH3CH(CH3)CH2CH3
Deflect
MOST
Deflect
LEAST
CH3CH(CH3)CH2CH3
+
Ionization
CH3
+
Fragmentation
Ionization of CH3CH(CH3)CH2CH3
CH3CH(CH3)CH2CH3 + e → CH3CH(CH3)CH2CH3
+
+ 2e → 72
or
CH3CH(CH3)CH2CH3 + e → CH3CH(CH3)CH2
+.CH3 +2e → 72
or
CH3CH(CH3)CH2CH3 + e → CH3CH(CH3)+.CH2CH3 + 2e → 72
Mass spectrum CH3CH(CH3)CH2CH3IonizationCH3CH(CH3)CH2CH3
Fragmentation of M+
CH3CH(CH3)CH2
+ - 57
CH3CH(CH3)+ – 43
CH3CH2
+ – 29
CH3
+ - 15
CH3CH(CH3)+
15
CH3CH(CH3)CH2
+
CH3CH(CH3)CH2CH3
+
CH3CH2
+
CH3CH(CH3)CH2CH3
+- 72
CH3CH(CH3)CH2
+ – 57
CH3CH(CH3)+ - 43
CH3CH2
+ – 29
CH3
+ – 15
Ionization and FragmentationProcess
CH3
+ CH3CH(CH3)CH2CH3
+

17. (C(CH3)4)+
- 72 - m/z highest –deflect LEAST
(C(CH3)3)+
– 57
(C(CH3)2)+
- 42
(C(CH3))+
– 27
CH3
+ –15 - m/z lowest - deflect MOST
Ionization/ Fragmentation pattern C(CH3)4
Deflect
MOST
Deflect
LEAST
Ionization
Fragmentation
Ionization of C(CH3)4
C(CH3)4 + e → (C(CH3)4)+ +2e → 72
Mass spectrum C(CH3)4IonizationC(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))+
– 27
CH3
+ –15
Fragmentation M+
(C(CH3)3)+
– 57
(C(CH3)2)+
- 42
(C(CH3))+
– 27
CH3
+ –15
Ionization and FragmentationProcess
CH3
+ (C(CH3)4)+
CH3
‫׀‬
CH3-C-CH3
‫׀‬
CH3

18. Ionization/ Fragmentation pattern CH3(CH2)8CH3
Ionization
Fragmentation
Ionization of CH3(CH2)8CH3
CH3(CH2)8CH3 + e → CH3(CH2)8CH3
+
+ 2e → 142
Mass spectrum CH3(CH2)8CH3Ionization
CH3(CH2)8CH3
CH3(CH2)8CH3
+
CH3(CH2)8CH3
+
= 142 - m/z highest – deflect LEAST
CH3(CH2)7CH2
+
= 127
CH3(CH2)6CH2
+
= 113
CH3(CH2)5CH2
+
= 99
CH3(CH2)4CH2
+
= 85
CH3(CH2)3CH3
+
= 71
CH3(CH2)2CH2
+
= 57
CH3CH2CH2
+
= 43
CH3CH2
+
= 29
CH3
+
= 15 – m/z lowest – deflect MOST
Loss of methylene
gp, CH2 = 14
CH3(CH2)8CH3
CH3(CH2)7CH2
+
= 127
CH3(CH2)6CH2
+
= 113
CH3(CH2)5CH2
+
= 99
CH3(CH2)4CH2
+
= 85
CH3(CH2)3CH3
+
= 71
CH3(CH2)2CH2
+
= 57
CH3CH2CH2
+
= 43
CH3CH2
+
= 29
CH3
+
= 15
Deflect LEAST
CH3
+
Deflect
MOST
CH3(CH2)8CH3
+
Ionization and FragmentationProcess
15

19. Ionization/ Fragmentation pattern CH3(CH2)8CH3
Ionization
Fragmentation
Ionization of C6H5CH2OH
C6H5CH2OH+e → C6H5CH2OH+
+ 2e → 108
Mass spectrum CH3(CH2)8CH3Ionization
C6H5CH2OH+ = 108 - m/z highest – deflect LEAST
C6H5CH2
+
= 91
C6H5
+
= 77
CH2OH+ = 31
OH+ = 17 – m/z lowest – deflect MOST
C6H5CH2OH C6H5CH2OH+
C6H5CH2OH
C6H5CH2OH+
C6H5CH2
+
= 91
C6H5
+
= 77
CH2OH+ = 31
OH+ = 17
C6H5CH2OH+ = 108
C6H5CH2
+
= 91
C6H5
+
= 77
CH2OH+ = 31
OH+ = 17
OH+
Deflect
MOST
Deflect LEAST
Ionization and FragmentationProcess

20. 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 !
Fragmentationpeak
(M - 15)+ = 45 -> (CH2CH2OH)+
(M - 29)+ = 31 -> (CH2OH)+
(M - 31)+ = 29 -> (CH3CH2)+
(M - 45)+ = 15 -> (CH3)+
Isomers of C3H8OH
Fragmentationpeaks
(M - 15)+ = 45 -> (CH3CH(OH))+
(M - 17)+ = 43 -> (CH3CHCH3)+
(M - 33)+ = 27 -> (CH3C)+
Vs
Loss of CH3
Loss of CH3CH2
Loss of CH2OH
Loss of CH2CH2OH
Loss CH3
OH OH
‫׀‬ ‫׀‬
CH3 C+·CH3 → CH3 C+
+ ·CH3
‫׀‬‫׀‬
H H
m/z= 45
CH3CH2CH2OH
OH
|
CH3CHCH3
Loss OH
Loss OH, CH3, H
Peak 29 and 31 are found
• Inductive effect of OH cause splitting of CH3CH2-|-CH2OH
• m/z = 29 peak detected – CH2CH3 present
CH3CH2
+
· CH2OH → CH3CH2
+
+ ·CH2OH
m/z= 29
CH3CH2
+
· CH2OH → CH3CH2 · + +
CH2OH
m/z= 31
Propan-1-ol
Propan-2-ol
15
Vs
Molecular Ion, M+
= 60 -> CH3CH2CH2OH+
Molecular Ion, M+
= 60 -> CH3CH(OH)CH3
+

21. Isomers, 2 methylbutanevs 2, 2 dimethylpropane
CH3
‫׀‬
CH3CHCH2CH3
CH3
|
CH3C-CH3
|
CH3
Peak 29 absent
• No CH3CH2
Peak 57 is higher
• Loss of methyl radical
produce tertiary carbocation
• Tertiary carbocation – More stable
Fragmentationpeaks
(M - 15)+ = 57 -> CH3CH(CH3)CH2
+
(M - 29)+ = 43 -> CH3CH(CH3)+
(M - 43)+ = 29 -> CH3CH2
+
(M - 57)+ = 15 -> CH3
+
Isomers of C5H12
Fragmentationpeaks
(M - 15)+ = 57 -> C(CH3)3
+
(M - 30)+ = 42 -> C(CH3)2
+
(M - 45)+ = 27 -> CH3C+
(M - 57)+ = 15 -> CH3
+
Vs
Loss of CH3
Loss of CH3CH2
Loss of CH3CH(CH3)
Loss of CH3CH(CH3)CH2
Loss of CH3
Loss of TWO CH3
Loss of THREE CH3
CH3
‫׀‬
CH3C+·CH3
‫׀‬
CH3
m/z= 57
CH3
‫׀‬
CH3 C+
+ ·CH3
‫׀‬
CH3
2 methylbutane
2, 2 dimethylpropane
Loss of C(CH3)3
Vs
Peak 29 absent
• CH3CH2 present
Molecular Ion, M+
= 72 -> CH3CH(CH3)CH2CH3
+
Molecular Ion, M+
= 72 -> C(CH3)4
+

22. Normal Vs High ResolutionMass 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 = 32
RAM, O = 16
RAM, N = 14
RAM, H = 1
RAM, C = 12
High ResolutionMass Spectrometer
Measure RMM to 4/5 decimalplaces
• 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 same
RAM, O = 15.9949
RAM, N = 14.0031
RAM, H = 1.0078
RAM, C = 12.0000
Vs
Vs
O2, N2H4, CH3OH
Same 32
O2 N2H4 CH3OH
different
Video how MS works
High resolution Mass spectrum

23. 37CI+ 35CI+
CI2 molecule
37CI-37CI - 74 - m/z highest – deflect LEAST
35CI-37CI –72
35CI-35CI –70
37CI –37
35CI –35 - m/z lowest– deflect MOST
Ionization/ Fragmentation pattern CI2
Deflect
MOST
Deflect
LEAST
35CI-35CI+
35CI+
35CI-37CI+
37CI-37CI+
Ionization
37CI+
37CI-37CI+
Fragmentation
Fragmentation of CI2
+
into CI+
CI+
.CI → [35
CI+
+ 35
CI·] + 2e – 35
CI+
.CI → [37
CI+
+ 37
CI·] + 2e –37
Ionization of CI2 to CI2
+
CI:CI + e- →[35
CI+
.35
CI] + 2e – 70
CI:CI + e- →[35
CI+
.37
CI] + 2e – 72
CI:CI + e- →[37
CI+
.37
CI] + 2e – 74
m/z = 37
m/z = 35
Ratio (35
CI : 37
CI) - 3:1
Mass spectrum CI2 / CI atom
Ratio (35
CI35
CI: 35
CI37
CI: 37
CI37
CI) - 9:6:1
IonizationCI2 molecule
37CI-37CI - 74
35CI-37CI – 72
35CI-35CI – 70
37CI – 37
35CI – 35
Ionization and FragmentationProcess

24. Br2 molecule
81Br-81Br - 162 - m/z highest – deflect LEAST
79Br-81Br –160
79Br-79Br –158
81Br –81
79Br –79 - m/z lowest– deflect MOST
Deflect MOST Deflect LEAST
79Br-79Br+
79Br+
79Br-81Br+
81Br-81Br+
Ionization
81Br+
79Br+
81Br-81Br+
Fragmentation
Fragmentation of Br2
+
to Br+
Br+
.Br → [81
Br+
+ 81
Br·] – 81
Br+
.Br →[79
Br+
+ 79
Br·] – 79
Ionization of Br2 to Br2
+
Br:Br + e- →[81
Br+
.81
Br] + 2e – 162
Br:Br + e- →[79
Br+
.81
Br] + 2e – 160
Br:Br + e- →[79
Br+
.79
Br] + 2e – 158
m/z = 79
m/z = 81
Ratio (79
Br : 81
Br) - 1:1
Mass spectrum Br2 / Br atoms
Ratio (79
Br79
Br: 79
Br81
Br: 81
Br81
Br) – 1:2:1
IonizationBr2 molecule
81Br-81Br - 162
79Br-81Br –160
79Br-79Br –158
81Br – 81
79Br – 79
Ionization/ Fragmentation pattern Br2
Ionization and FragmentationProcess

25. Ionization/ Fragmentationpattern CH3CH(CI)CH3
Ionization
Ionization
Ionization CH3CH(CI)CH3
CH3CH(CI)CH3+e → CH3CH(CI)CH3
+
+ 2e → 78/80
Presence isotope 35CI and 37CI
CH3CH(37CI)CH3
+ = 80 - m/z highest – deflect LEAST
CH3CH(35CI)CH3
+ = 78
CH3CH(37CI)+
= 65
CH3CH(35CI)+
= 63
CH3CHCH3
+ = 43
CH3C+ = 27 - m/z lowest – deflect MOST
CH3CH(37CI)+
=65
CH3CH(35CI)+
= 63
CH3CHCH3
+ = 43
CH3C+ = 27
CH3CH(CI)CH3 CH3CH(CI)CH3
+
CH3CH(CI)CH3
+
Isotopic peak
(M+)= 78
Isotopic peak
(M++2) = 80
CH3CH(35CI)CH3 CH3CH(37CI)CH3
Isotopic peak
63
Isotopic peak
65
CH3CH(35CI)+ CH3CH(37CI)+
CH3CH(CI)CH3 Fragmentation
CH3C+
Deflect MOST Deflect LEAST
Presence M+ and (M+
+ 2) peak
Presence of Isotopes
Ionization and FragmentationProcess

26. CH3CH2CH2
79Br CH3CH2CH2
81BrCH2CH2
79Br CH2CH2
81Br
Ionization/ Fragmentationpattern CH3CH2CH3Br
Ionization
Ionization
Ionization CH3CH2CH2Br
CH3CH2CH2Br+e → CH3CH2CH2Br+
+ 2e → 122/124
Presence isotope 79Br and 81Br
CH3CH2CH2
81Br+ = 124 - m/z highest – deflect LEAST
CH3CH2CH2
79Br+ = 122
CH2CH2
81Br+
= 109
CH2CH2
79Br+
= 107
CH2
81Br+ = 95
CH2
79Br+ = 93
CH3CH2CH2
+ = 43
CH3C+ = 27 - m/z lowest – deflect MOST
Isotopic peak
(M+) = 122
Isotopic peak
(M++2) = 124
Isotopic peak
107
Isotopic peak
109
Fragmentation
CH3C+
Deflect MOST Deflect LEAST
CH3CH2CH2Br CH3CH2CH2Br+
CH3CH2CH3Br
CH3CH2CH2Br+
CH2CH2
81Br+
=109
CH2CH2
79Br+
=107
CH2
81Br+ = 95
CH2
79Br+ = 93
CH3CH2CH2
+ =43
CH3C+ = 27
CH3C+
Deflect
LEAST
CH3CH2CH2Br+
Presence of M+ and (M+
+ 2) peak
Presence of Isotopes
Deflect
MOST
Ionization and FragmentationProcess

27. TI
IB Questions on Mass Spectrometer
Mass spectrometerused to investigateisotopiccompositionof elements.
Thallium has two isotopes.
1) State symbol of two singly chargedionsform.
2) State which ion will follow path marked X on diagram.
lighter-> DEFLECTED MORE
3) Doublychargedions form. Suggestreason whetherthey wouldbe deflectedless or
more than ions at X and Y.
DEFLECTED MORE. Cause deflectiondependson m/z ratio.
Low Mass + High charge -> m/z ratio is low -> deflectedmore.
Naturally occuringboronhas 2 isotopes.RAM boronis 10.81.
% abundance x% (100 – x)%
Determinepercentageabundanceof these isotopes.
Answer:Let % abundancebe x.
1
TI TI
203 205
81 81
X =
B10 B11
Relative Isotopic Mass:
= (Mass 10
B x % Ab) + (Mass 11
B x % Ab)
= (10 x x/100) + (11 x (100 – x)/100) = 10.81
X = 19%
TI+
81
203
TI+205
81
TI+
203
81

28. IB Questions on Mass Spectrometer
Germaniumis analysedin mass spec. The first and last processesare vaporizationand detection.
1) State the namesof other 3 processesin order in which they occur
Answer:Ionization-> Acceleration-> Deflection
2) For each of processesnamed in a (i), outlinehow processoccur
Ionization-> Sample bombardedwith highenergy/highspeed electrons
Acceleration-> Cations (+ve chargedions) acceleratedby an electricfield
Deflection-> Cations deflectedby a magneticfield
3) Germaniumfoundto have followingcomposition
i)Definerelativeatomic mass.
Average/ weightedmasses of all isotopesof an element.
ii) CalculateRAM, givinganswer to two decimal places.
2
RelativeIsotopicMass
= (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

29. IB Questions on Mass Spectrometer
Showsa mass spectrometer.
1)Identifythe parts labelledA, B and C.
2)State and explainwhich one will undergogreatest deflection.
Answer : Greatestdeflection-> lowest mass + highestcharged -> m/z -> lowest
3) Mass spectrumshown below:
i) Explainwhy thereis more than one peak.
Existence of isotopes
ii) Calculate RAM.
3
Relative Isotopic Mass
= (Mass 24Y x % Ab) + (Mass25Y x % Ab) + (Mass 26Yx % Ab)
= (24 x 79/100)+ (25 x 10/100)+ (26 x 11/100) = 24.32
• electron gun
• ionisation chamber
• ionizer
• Electric field
• Charged plates
• Potential difference
• Magnetic field
• Magnet
• Electromagnet
greatest deflection – low mass, high charged
smallest deflection – high mass, low charged
A
C
B
Li+
Li2+
7
6

30. IB Questions on Mass Spectrometer
Vaporizedmagnesiumis introducedintomass spec. One of the ionsthat reachesdetectorshown below.
1)Identifynumberof protons,neutronand electrons
Answer: 12 protons,13 neutrons,11 electrons
2) State how ion is acceleratedin mass spectrometer.
Using a strong electricfield/strongoppositechargedplate/potentialdifference
3) The ion is also detected by changingthe magnetic field. Deduceand explainby referenceto
m/z valuesof these two ionsof magnesium,which of the ions and is detectedusing a stronger
magneticfield.
Answer: - due to lower charge -> m/z is higher-> deflectedless -> needsa strongermagneticfield to deflect.
4
Cations (+ve) acceleratedby (-ve) plates
25
12
25Mg 2+
smallest deflection – high mass, low charged
Strong magnet/magnetic field to deflect it to bottom
Mg +
25Mg 2+ 25Mg +
25Mg +
25Mg +

31. Rubidiumcontainstwo stable isotopes.RAM for rubidiumis 85.47
1)Calculate % of each isotopein rubidium.
Answer : Let % abundancebe x %.
% Abundance x% (100 – x)%
76.5% 23.5%
2) Vaporizedsample is ionizedand accelerated.How the use of magneticfieldand detectorenablespercentageof two
isotopesto be determined.
5
85 87
Relative Isotopic Mass:
= (Mass 85
Rb x % Ab) + (Mass 87
Rb x % Ab)
= (85 x x/100) + (87 x (100 – x)/100) = 85.47
X = 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 sample
•Ratio of height of peaks due to
85Rb : 87Rb –> 76.5 : 23.5
Magnetic field/Deflector
• M+ ion deflected by magnetic field
- lighter -> deflectedmore
- heavier -> deflectedless
IB Questions on Mass Spectrometer
Rb Rb
85 Rb 87 Rb
85 Rb 87 Rb
85 Rb
87 Rb