Introduction
working principle
fragmentation process
general rules for fragmentation
general modes of fragmentation
metastable ions
isotopic peaks
applications
Introduction
working principle
fragmentation process
general rules for fragmentation
general modes of fragmentation
metastable ions
isotopic peaks
applications
MASS SPECTROSCOPY ( Molecular ion, Base peak, Isotopic abundance, Metastable ...Sachin Kale
CONTENT:
Molecular Ion Peak
Significance of Molecular ion & Graphically Method
Base Peak
Isotopic Abundance
Metastable Ion
Significance of Metastable ion
Nitrogen Rule & graphs
Formulation of Rule
PRINCIPLES of FT-NMR & 13C NMR
Fourier Transform
FOURIER TRANSFORM NMR SPECTROSCOPY
THEORY OF FT-NMR
13C NMR SPECTROSCOPY
Principle
Why C13-NMR is required though we have H1-NMR?
CHARACTERISTIC FEATURES OF 13 C NMR
Chemical Shifts
NUCLEAR OVERHAUSER ENHANCEMENT
Short-Comings of 13C-NMR Spectra
MASS SPECTROSCOPY ( Molecular ion, Base peak, Isotopic abundance, Metastable ...Sachin Kale
CONTENT:
Molecular Ion Peak
Significance of Molecular ion & Graphically Method
Base Peak
Isotopic Abundance
Metastable Ion
Significance of Metastable ion
Nitrogen Rule & graphs
Formulation of Rule
PRINCIPLES of FT-NMR & 13C NMR
Fourier Transform
FOURIER TRANSFORM NMR SPECTROSCOPY
THEORY OF FT-NMR
13C NMR SPECTROSCOPY
Principle
Why C13-NMR is required though we have H1-NMR?
CHARACTERISTIC FEATURES OF 13 C NMR
Chemical Shifts
NUCLEAR OVERHAUSER ENHANCEMENT
Short-Comings of 13C-NMR Spectra
This power point was prepared based on Introduction to Spectroscopy by L. Pavia, Gary M. Lampman, and George S. Kriz. The language of this power point is Persian.
MS Fragmentation Process and Application of MS.pdfDr. Dinesh Mehta
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).
MS Fragmentation Process and Application of MS.pdfDr. Dinesh Mehta
Fragmentation process:
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).
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
Isotopes are two atoms of the same element that have the same number of protons but different numbers of neutrons. Isotopes are specified by the mass number.
Content:
Basic concepts
Fragmentation Process
McLafferty Rearrangement
Mass spectrum
Metastable ion
Isotopic peak
Nitrogen Rule
Basic Concept:
Mass spectrometry uses high energy electrons to break a molecule into fragmentation.
A beam of high-energy electrons breaks the molecule apart.
The masses of the fragments and their relative abundance reveal information about the structure of the molecule.
Separation and analysis of the fragments provides information about:
– Molecular weight
– Structure
Fragmentation Process
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".
McLafferty Rearrangement:
Fragmentation due to rearrangement of Molecular or Parent ion:
The cleavage of bonds in Molecular ion is due to the intramolecular atomic rearrangement. This leads to fragmentation whose origin cannot be described by simple cleavage of bonds.
When fragments are accompanied by bond formation as well as bond for breaking, a rearrangement process is said to have occurred.
Such rearrangement involves the transfer of hydrogen from one part of the molecular ion to another via, preferably, a six-membered cyclic transition state.
This process is favoured energetically because as many bonds are formed as are broken.
Compounds containing hydrogen atom at position gamma to carbonyl group have been found to a relative intense peak.
This is probably due to rearrangement and fragmentation is accompanied by the loss of neutral molecule. This rearrangement is known as Mc Lafferty rearrangement.
Thus , the molecular formula of the unknown compound can be determined from the various fragment ions and also the parent ion of the mass spectrum .
More example of McLafferty reaarangements are :
A double McLafferty rearrangement is also reported in ketones .
The second hydrogen atom originates exclusively from the γ – position .
A secondary hydrogen is preffered to a primary hydrogen atom in this process . The mechanism involves.
Ketonisation of the intermediate enol ion by the hydrogen transfer .
Hydrogen transfer to enolic oxygen . Consider the McLafferty rearrangement in 4- Heptanone.
Mass Spectrum :
It is a record of the masses and the relative abundances of the molecular ion and the positively charged fragments formed from it by the electron bombardment.
The molecular ion or Parent ion :
The electron bombardment with energy 10-15 eV usually removes one electron from the molecule of the organic compoound in the vapour phase it results in the formation of molecular ion
The mass of the parent ion gives the molecular mass of the sample. .
In mass spectrometry, fragmentation is the dissociation of energetically unstable molecular ions formed from passing the molecules in the ionization chamber of a mass spectrometer. The fragments of a molecule cause a unique pattern in the mass spectrum.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Ethnobotany and Ethnopharmacology:
Ethnobotany in herbal drug evaluation,
Impact of Ethnobotany in traditional medicine,
New development in herbals,
Bio-prospecting tools for drug discovery,
Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
This is a presentation by Dada Robert in a Your Skill Boost masterclass organised by the Excellence Foundation for South Sudan (EFSS) on Saturday, the 25th and Sunday, the 26th of May 2024.
He discussed the concept of quality improvement, emphasizing its applicability to various aspects of life, including personal, project, and program improvements. He defined quality as doing the right thing at the right time in the right way to achieve the best possible results and discussed the concept of the "gap" between what we know and what we do, and how this gap represents the areas we need to improve. He explained the scientific approach to quality improvement, which involves systematic performance analysis, testing and learning, and implementing change ideas. He also highlighted the importance of client focus and a team approach to quality improvement.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
1. FRAGMENTATION TECHNIQUES IN MASS
SPECTROSCOPY
Presented by:
Sk.Samiya,
1st year M-Pharm,(Pharmacology)
Hindu College of Pharmacy
2. Mass spectroscopy
Definition:
It is a powerful analytical technique useful for determination of
molecular weight of compound.
Principle:
Initially in mass spectroscopy the sample must be converted into
vapourised or gaseous form then it undergo ionization to form a
molecular ion with the liberation of 1e-.
This molecular ion normally undergoes fragmentation to form several
fragmented ions or daughter ions.
3. FRAGMENTATION
The process of breaking up of molecular ion into smaller or daughter
ions is known as “fragmentation”.
The molecular ion commonly decomposes to a pair of fragments,
which may be either a radical with an ion or a small molecule & a
radical cation.
4. Fragmentation process
Bombardment of molecules by a 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 50-7ev,
these molecular ions acquire a high excitation resulting in their
break down into various fragments.
5. General modes of fragmentation
Fragmentation of the molecular ion takes place in following mods:
Simple cleavage
1. Homolytic cleavage
2. Heterolytic cleavage
3. Semi heterolytic cleavage
Rearrangement reactions
1. Elimination reactions
2. Ortho reaction
3. Mc-lafferty rearrangement
6. Simple cleavage:
Transfer of electrons takes place
1. Homolytic cleavage
In hemolytic cleavage the electrons are equally transferred to both
atoms & it forms radical and cation.
R
H2C
CH
CH2
R
H2C
CH
CH2
R
+
CH
HC
CH2
IONISATION
HOMOLYTIC
CLEAVAGE
7. 2. Heterolytic cleavage
Fragmentation by movement of two electrons:
In this type of cleavage both the electrons of the bond are taken over
by one of the atoms; the fragments are an even electron cation and a
radical with the positive charge residing on the alkyl group.
C4H9I
ionisation
CH3
CH2
+ I
C4H9I
HETEROLYTIC
CLEAVAGE
8. 3.Semi heterolytic cleavage
In this one electron bond cleavage takes place resulting in formation
of radical & cation.
C
H
H H
H
C
H
H H
H
CH3
+
H
IONISATION CLEAVAGE
9. Rearrangement reaction
It involves the cleavage of bonds and formation of new bonds i.e., it
requires changes to at least two bonds.
So the produced ions are not structural units of precursors.
Generally rearrangement leads to loss of smaller molecules.
10. 1. Elimination reaction
In his fragmentation hydrogen is obstructed by hydroxyl group or
halogen or acetate functional groups results in the elimination of water
or neutral molecule.
R – CH2 – CH2 –CH2 R – CH2 – CH2 – CH2 +
OCOCH3 OCOCH3
CH3COOH + R – CH2 – CH = CH2
11. 2. Ortho effect reaction
In the case of substituted aromatic compounds the substitute & carbon come into
proximity has help in elimination of neutral molecule. This effect is called ortho
effect.
O
O
CH3
CH3
O
O
CH3
C
H2
C
O
CH2
+
OCH3
H
C
C
C
O
CH2
+ CH3OH
methyl 2-methylbenzoate
methyl 2-methylbenzoate ion
(6-methylenecyclohexa-2,4-
dienylidene)methanone
H
12. 3. Mc-Lafferty rearrangement reaction
The loss of an alkene fragment by cyclic rearrangement of a carbonyl
compounds ( like aldehyde, ketones, acids, esters, amines),
unsaturated compounds with γ-hydrogens undergo Mc-Lafferty
rearrangement.
Or
It involves the migration of γ-hydrogen atom followed by cleavage
of β-bond then rearrangement leads to the elimination of neutral
molecule.
13. Mechanism
Fragmentation takes place only at γ-hydrogen
Then this hydrogen is obstructed by oxygen of carbonyl group or
unsaturated compound.
Carbonyl group is converted to hydroxyl group
Bond break down between α & β carbons resulting in liberation of 2e-’s
then rearrangement takes place to form a simple alkene.
17. REFERENCES:
Instrumental methods of chemical analysis- B.K Sharma,
Instrumental methods of analysis By Chatwal,
Principles of Instrumental analysis By Donglas Skoog
