this ppt contain all basic information related to the mass spectrometry like introduction, principle of MS, type of ions, fragmentation processes eg. mcLafferty rearrangement, alpha clevage, sigma bond clevage, retro-diels-alder reaction

1. MASS
SPECTROMETRY
Presented by -
Jamdhade Vaishali K.
(M. Pharm F.Y. Pharmaceutics)
Guided by -
Mr. Mohite Mukesh

2.  Introduction
 Basic principle
 Fragmentation
 Types of ions
 Fragmentation processes
CONTENT
1

3.  Mass spectrometry (MS) is an analytical
technique in which sample is converted to rapidly
moving positive ions i.e. cations by electron
bombardment and separate the ions on the basis of
their Mass to charge ratio.
INTRODUCTION
 In simple terms mass
spectrum measures the
masses within the sample.
2

4.  In mass spectrometer parent ions are formed by
removal of electron as follows:
M(g) + e M+(g) + 2e
 The m/e value of the parent ion is equal to the
molecular mass of the compound.
 The mass spectrometer is designed to perform 3
basic functions. These are:
i. To vapourise compounds.
ii. To produce ions from the neutral compounds
in the vapour phase.
iii. To separate ions according to their mass to
charge ratio. 3

5. MASS SPECTRUM OF BROMINE
4

6. What is Mass Number…?
The Mass Number (A), also called as atomic mass
number is the total number of protons (Z) and
neutrons (N) in atomic nucleus.
Mass
Number
(A)
No. of
Neutrons
(N)
+
No. of
Protons
(Z)
5

7. 6

8. PRINCIPLE
Organic molecule are bombarded with electron
Converted into highly energetic cations
(Molecular ion or Parents ions)
Further break up into smaller ions
(Fragment ion or daughter ions)
The formed ions are separated into deflection in
magnetic field according to mass to charge ratio
Mass spectrum 7

9. 8

10. FRAGMENTATION
 Bombardment of molecules by an electron beam
with energy between 10-15eV usually results in the
ionization of molecules by removal of one electron
(Molecular ion formation).
 When the energy of electron beam is increased
between 50-70ev, these molecular ions acquire a high
excitation resulting in their break down into various
fragments. This process is called “ Fragmentation
process”.
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12. 12
Fragment ions /
Daughter ions.
TYPES OF IONS
Molecular ions /
Parent ion.

13. 1. When a molecule is bombarded with electrons in
high vacuum in Mass spectrometer, it is converted into
positive ions by loss of an electron. These ions are
called as Molecular or Parent ions.
M + e  M+° + 2e—
Where,
M – represents the Molecule;
M+°– represents the Molecular or Parent ion
MOLECULAR IONS / PARENT IONS
2. The order of energy required to remove electron is
as follows—
 electrons > non-conjugated  > conjugated  >
non bonding or lone pair of electrons. 13

14. FRAGMENTATION OF MOLECULAR
IONS
14

15. FRAGMENT IONS / DAUGHTER ION
• An electrically charged dissociation product of an
ionic fragmentation. Such an ion may dissociate
further to produce other electrically charged
molecular or atomic moieties of successively lower
formula weight.
• This ions are formed from breakdown of molecular
ions in to smaller ions.
• Also called as Daughter ion.
• Examples of common fragment ions are as
follows:
15

16. Sr. No Ions m/e
1 CH3 15
2 O 16
3 OH 17
4 Cl 35,37
5 NO2 46
6 CN 26
7 C6H5 77
16

17. TYPES OF PEAKS IN MS
1. Molecular peak
2. Fragment peak
3. Rearrangement ion peak
4. Base peak
5. Metastable ion peak
6. Multicharged ions

18. Molecular Peak
When the sample is bombarded with electron of 9 to 15 eV
energy, the molecular ions are produced molecular ion, by loss
of single electron.
Fragment ion Peak
When energy more than 70 eV are applied, then fragment ion
are produced. They have lower mass number.
Rearrangement ion Peak
Recombination of fragment ion is known as rearrangement
peaks.
Multiple charged Peak
This ion may have 2-3 charge instead of single charge
18

19. 1. α - cleavage
2. Sigma bond cleavage
3. Inductive cleavage
4. McLafferty rearrangement
5. Retro-Diels-Alder reaction
TYPES OF FRAGMENTATION
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20. 20
 Alpha fragmentation in MS is characteristic
fragmentation of molecular ion derived from
Carbonyl compound , in which the bond linking
the carbonyl carbon to atom shows alpha bond
breaks.
 It is expected pathway for following functional
groups - Ether
Alcohol
Halide
Amines
Carbonyl compound
α - Cleavage

22. Sigma Bond Cleavage
 The ionization of alkanes weakens the C-C bond,
ultimately resulting in the decomposition.
 As bond breaks, A charged, even electron species
(R+) and a neutral radical species (R•) are
generated.
 Highly substituted carbocations are more stable
than the nonsubstituted ones.
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23. Inductive Cleavage
 This reaction results from the inductive effect of
the radical sites.
 This reaction is defined as a Heterolytic
Cleavage since a pair of electrons is transferred.
 The driving forces for such reaction are the
electronegativities of the radical sites:
halogens > O, S >> N, C.
 This reaction is less favored than radical-site
reactions.
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24. McLafferty Rearrangement
 This involves migration of gamma- hydrogen
atom followed by the cleavage of β-bond.
 Elimination of neutral molecules from
aldehydes, ketone, amine, unsaturated
compounds, substituted aromatic compound etc
takes place.
 The rearrangement proceeds through a sterically
hindered 6 membered transation state.
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25. 24
 This rearrangement can occur in :-
Ketone
Aldehyde
Carboxylic acid
Ester

26.  Butanal contaions a gamma-hydrogen atom. The
McLafferty rearrangement ions formed in this
case is shown below-
25
Example – Butanal

27. Retro-Diels -Alder Rearrangement
• This reaction occurs mainly in Cyclohexene and
its derivatives.
• In this first ionization occur and electrons from
double bond transfers to the adjacent carbon and
the electron from the bond between the 3-4 carbon
atom transfer to from a double bond that is
conjugate with the first one.
• This rearrangement cleave the molecule between
3 and 4, and 5 and 6 carbon atom.
• This rearrangement produces olefin and a diene.
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29. THANK YOU