1. SHRI. SHIVAJI COLLEGE OF ARTS,
COMMERCE, AND SCIENCE,
AKOLA
Presented by
Miss. Ankita R. Gajabhiye
Msc 2nd year (Sem 3rd)
chemistry
mass Seminar Topic : Mass
Spectroometry
opic : mass spectroometry
3. INTRODUCTION
•Mass spectrometry is an analytical technique
that measure the mass to charge particles.
•It is used for determining masses of particles
for determining the elemental composition of a
sample or molecule.
•Mass spectrometry is a powerful technique for
identifying unknown compound, studying
molecular structure, and probing the
fundamental principles of chemistry.
4. BASIC PRINCIPLES
It is a most accurate method for determining the
molecular mass of the compound and elemental
composition.
•In this technique, the compound under
investigation is bombarded with beam of
energetic electrons.
•The molecules are ionised or dissociate into
several fragments, some of which are positive
ions.
•Each kind of ions has a particular ratio of mass
to charge i.e m/e ratio.
6. THEORY
•A mass spectrum consist of an array of peaks of
different heights.
•The nature of the spectrum is dependent on
properties of the molecule, ionisation potential,
sample pressure and the instrument design.
•The mass spectrometer bombards a molecule M with
high energy electrons.
M+e– -----------> M+ + 2e–
9. FRAGMENTATION
• The fragmentation pattern, i.e, The break up process of
molecular ion into smaller ions, called fragment ions or
daughter ions.
• The fragmentation of even simple molecules produces a large
number of ions of different masses.
• A complex spectrum is obtained which often permits
identification of compound or recognition of the presence of
functional group in compounds.
• It should be noted that all fragments ions are not of equal
significance in ascertaining the structure of the compound.
11. • There are two important types of fragmentations:
1. A neutral molecule such as H2O, CO, C2H4, HCl, HCN, etc. is
eliminated. This loss of a neutral molecule gives a new
fragment whose mass number has the same parity i.e., odd or
evenness as the parent.
2. Fragmentation parents may involve a seperation into the ion
part and the radical part and this process channge the parity.
The elimination of neutral fragments gives new radical cations,
which are knows as odd electron fragments, while those formed
by the elimination of a free radical are know as even electron
fragments. This rule is of great significance in deciding the mode
of fragmentation.
The loss of and alkene fragment by a cyclic rearrangement of a
carbonyl compound with γ-hydrogens is known as mclafferty
12. MCLAFFERTY REARRANGEMENT
• It is a very is a very common fragmentation reaction observed
in a mass spectrometry.
• This fragmentation was first described by Fred Mclafferty in
1956.
• For maclafferty reaction molecule must contain at least on
gamma hydrogen and the functionality which can form radical
cation.
general structure of molecule
Z=C, N,O
13. It involve cleavage of a α – β bond followed by transfer of γ – H atom.
This rearrangement leads to the elimination of neutral atom like,
