The document discusses mass spectrometry and provides information on various topics related to it including:
- Types of ions produced including molecular ions, fragment ions, and metastable ions.
- Common fragmentation patterns for different functional groups such as alkanes losing alkyl groups, alkenes forming allylic ions, and aromatics fragmenting at benzylic carbons.
- General rules for fragmentation including favored cleavage at branched points and loss of the largest substituent from a branch.
- Examples of mass spectra and prominent peaks are shown for compounds like ethanol, 2-pentanone, and hydrocinnamaldehyde to illustrate fragmentation patterns.
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.
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.
Introduction
working principle
fragmentation process
general rules for fragmentation
general modes of fragmentation
metastable ions
isotopic peaks
applications
Two dimensional Nuclear Magnetic Resonance (2D NMR) refers to a set of multi pulse techniques which were introduced to overcome the complex spectra obtained with NMR.
It is a set of NMR methods which give data plotted in a space defined by two frequency axes rather than one.
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
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
Introduction
working principle
fragmentation process
general rules for fragmentation
general modes of fragmentation
metastable ions
isotopic peaks
applications
Two dimensional Nuclear Magnetic Resonance (2D NMR) refers to a set of multi pulse techniques which were introduced to overcome the complex spectra obtained with NMR.
It is a set of NMR methods which give data plotted in a space defined by two frequency axes rather than one.
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
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
A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the electrostatic force of attraction between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bond
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.
chemical bonding and molecular structure class 11sarunkumar31
hybridisation, bonding and antiboding, dipole moment, VSPER theory, Molecular orbital diagram, Phosphorous pentachloride, ionic bond, bond order, bond enthalpy, bond dissociation, sp and sp2hybridisation, hydrogen bonding,electron pair,lone pair repulsion, resonance structure of ozone, how to find electron pair and lone pair, sp3 hybridization of methane.
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
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
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
2. Contents
Introduction of Mass spectrum.
Types of Ions
Molecular ion,
Metastable ions,
Fragment ions.
Fragmentation procedure
Fragmentation patterns
Fragment characteristics
Relative abundances of isotopes.
2
3. Introduction of MS
The impact of a stream of high energy electrons causes the
molecule to lose an electron forming a radical cation.
A species with a positive charge and one unpaired electron
H
H C H
H
+
-
e
H
H C H
-
+ 2e
H
Molecular ion (M+)
m/z = 16
3
4. Introduction of MS
Only cations are detected.
- Radicals are “invisible” in MS
The amount of deflection observed depends on the mass to
charge ratio (m/z).
-Most cations formed have a charge of +1 so the amount of
deflection observed is usually dependent on the mass of
the ion.
.
4
5. Molecular ion
Base peak
M+
Radical cation
Fragment ions
The ion obtained by the loss of an electron from the
molecule also called parent ion
The most intense peak in the MS, assigned 100%
intensity
Symbol often given to the molecular ion.
Mol. With an unpaired e+ve charged species with an odd number of electrons
Lighter cations formed by the decomposition of the
molecular ion. also called daughter ion
6. Mass Spectrum
The resulting mass spectrum is a graph of the mass of each
cation vs. its relative abundance.
Relative abundance of an ion means the % of total ion
current.
Mass spectrum is an analytical techniques which can provide
information concerning the molecular structure of organic
comp.
Base peak is the highest peak or the most intense peak in the
spectrum.
6
7. Types of Ion
Types of ion produced in MS
1.Molecular ions (parent ion)
2.Metastable ions
3.Fragment ions (Dissociation process)
4.Rearrangement ions
5.Multiple charged ions
6.Isotopes ions
7.Negative ions
8.Base peak
7
8. Molecular ion
Molecular ion (parent ion):
-The radical cation corresponding to the mass of the
original molecule
H
H C H
H
H C C H
H H
H H
The molecular ion is usually the highest mass in
the spectrum
8
9. Molecular ion
When a sample sub.is bombarded with electrons
of energies of 9 to 15eV, the molecular ion
is produced by loss of a single electron.
This will give rise to a very simple mass spectrum
with essentially all of the ion appearing in one
peak called parent peak.
M + e = M+ + 2e-
Most important ion.
9
10. Molecular ion
In organic compound there is generally a small peak
appearing one mass unit higher than the parent peak
(M+1) due to small but observable ,natural abundance
of C13 and H2 in these compound.
The relative height of parent peak decreases in the
following order,
aromatic>conjugated olefins>sulphides>
unbranched>hydrocarbon>ketones>amine>ester>
ethers >carboxylic acid>branched hydrocarbons.
10
11. Molecular ion
If a molecule yields the parent peak due to molecular
ion ,the exact molecular weight can be calculated.
Molecular ion are formed in the ground state and in
the electronically excited state.
11
14. Fragment ion
The molecular ion produced in MS is generally left
with considerable excess energy.
This energy is rapidly lost by the molecular ion
resulting in one or more cleavages in it with or without
some rearrangement.
One of the fragment retains the charge where as the
remaining fragment may be stable molecule or
radicals.
14
15. Fragment ion
If the electron beam energy is further increased to
apparent potential of a molecule ,then the excited
molecule ions undergoes decomposition to give rise to
variety of fragment ions which leaves smaller masses
than the molecular ion.
Formed by both heterolytic and homolytic cleavage of
bond.
They are formed by simple cleavage and
rearrangement process.
15
16. Fragment ion
Bond dissociation energy stability of neutral fragment
are steric factors are some of the major factor which
determine formation of fragment ions.
E.g. : Ethyl chloride.
CH3-CH2-Cl + e- = CH3-CH2-Cl + + 2e-
CH3-CH2-Cl + = CH3-CH2+ + Cl. Or
CH2-CH2+ + HCl. (Fragment ion)
16
17. M + e-
M+* + 2e-
OR
+*
1
M
+
M2
M4+
Fragmentation Process
+
M3*
18. Metastable ion
The ions in a mass spectrometer that have sufficient
energy to fragment sometime after leaving the ion
source but before arriving at the detector.
M+
(m1/z)
M+ with large amount of internal energy will fragment
in the ionization source, producing “normal” A+ ions.
These A+ ions will be seen as narrow peaks at m/z
values correct for the mass and charge on the ion A+.
M+ having only a small excess of internal energy,
reach detector before decomposition can occur.
Narrow peaks for “normal” M+ appear
A+ + N
(m2/z) (m1-m2)
18
19. Metastable ion
M+ which posses excesses of internal energy that are
in between the those in above two cases, may
fragment after leaving the ion source and before
reaching the detector. The product ions, A+, are seen
in the mass spectrum as broad peaks, centered at m/z
values that are nor correct for the mass and charge on
the ion A+.
These broad peaks are called “metastable ion peaks”
These ““metastable ion peaks” do not represent
metastable M+ ions, but represent products of
decomposition of metastable ions.
The cause of A+ ions from metastable ion
decomposition being detected differently form “normal”
A+ ions is due to their different momentum.
19
20. FRAGMENTATION MODES
The RA of fragment ion formed depends upon’
1)The stability of the ion
2)Also the stability of radical lost.
The radical site is reactive and can form a new bond.
The formation of new bond is a powerful driving force for
ion decompositions.
The energy released during bond formation is available for
the cleavage of some bonds in the ion.
Some imp. Fragmentation modes are described below
1)Simple cleavage :
Involves i) Homolytic or
ii) Heterolytic cleavage
of a single covalent bond.
20
21. Fragmentation modes
1) Homolytic cleavage :
odd electron ions have unpaired electron which is
capable of new bond formation.
Bond is formed , energy is released , help offset the
energy required for the cleavage of some other bond in
the ion.
Homolytic cleavage reactions are very common.
2) Heterolytic cleavage :
It may be noted the cleavage of C-X (X=
0,N,S,Cl) bond is more difficult than that of C-C bond.
In such cleavage , the positive charge is carried by the
carbon atom and not by the heteroatom.
R-CH2-Cl.+ = Cl. + RC+H2
21
22. Fragmentation modes
2) Retro –Diels –Alder reaction
The reaction is an example of multicentre
fragmentation which is characteristic of cyclic olefins.
It involves the cleavage of two bonds of a cyclic system ,
result the formation of 2 stable unsaturated fragment in
which 2 new bonds are formed.
This process is not accompanied by any hydrogen
transfer rearrangement.
The charge can be carried by any one of the fragment.
22
23. •
•
3)Mc Lafferty Rearrangement:
This involves migration of hydrogen atom from one part of the ion to
another.
To undergo a Mc Lafferty Rearrangement a molecule must possess
a) An appropriately located heteroatom e.g. O, N
b) A pi electron system ( usually a double bond) &
c) An abstractable hydrogen atom gamma to the C = X system
Gamma hydrogen atom is transferred through a six membered transition
state to an electron deficient centre followed by cleavage at beta
bond.
The reaction results in the elimination of a neutral molecule.
23
26. Rules
A number of general rules for predicting prominent peak
in electron impact spectra are recorded and can be
summarized below
1) most compound give molecule ion peak but some do
not . Existence of molecular ion peak in the spectrum is
dependent on the stability of molecule
2)In case of alkenes , the relative intensity of the
molecule ion peak is greatest for the straight chain
compound but,
a) The intensity decreases with increases degree of
branching.
b) The intensity decreases with increasing molecular
weight in a homologous series.
26
27. Rules
3) cleavage is favored at alkyl substituted carbons ,the
more substituted ,the more likely is the cleavage .Hence
the tertiary carbocation is more suitable than secondary,
which is more turn stable then primary. The cation
stability order is CH3 < R-CH2 <R2 CH+ <
R3C+.Generally the largest substituent at a branch is
eliminated most readily as a radical, presumably
because a long chain radical can achieve some stability
by delocalization of the lone electrons.
4)In alkyl substituted ring compounds, cleavage is
favoured at the bound at the bond beta to the ring giving
the resonance stabilized benzyl ion.
5)Saturated rings containing side chain, lose the side
chains at the alpha bond. the ve+ charge tend to stay
with ring fragment.
27
28. Rules
6)The cleavage of a C-X bond is more difficult than that
of a C-C bond (X=O, N, S, F, CI, etc). If occurred ,the
positive charge is carried by the carbon atoms, and not
to the heteroatom.the halogens having great electron
affinity do not have tendency to carry the positive
charge.
7)Double bonds favour allylic cleavage and give the
resonance stabilized allylic carbonium ion.
8)Compounds containing a carbonyl group tend to break at
this group with positive charge remaining with the
carbonyl portions.
28
29. Rules
9)During fragmentation, small, suitable neutral molecules
e.g. water, carbon monoxide, alcohol, ammonia,
hydrogen cyanide, carbon dioxide, ethylene etc,
are eliminated from appropriate ions.
29
30. Fragmentation Pattern for org. comp.
Organic molecules will fragments in very specific ways
depending upon what functional groups are present in the
molecule.
These fragments (if positively charged are detected in
mass spectroscopy)
The presence or absence of various mass peaks in the
spectrum can be used to deduce the structure of the
compound in question.
30
31. Fragmentation rules in MS
1. Intensity of M.+ is Larger for linear chain than
for branched compound
2. Intensity of M.+ decrease with Increasing MW.
(fatty acid is an exception)
3. Cleavage is favored at branching
reflecting the Increased stability of the ionR
Stability order: CH3+ < R-CH2+ <
R CH
R
R
CH+ < R C+
R
R’
R”
Loss of Largest Subst. is most favored
31
32. Fragmentation Patterns
The impact of the stream of high energy electrons
often breaks the molecule into fragments, commonly a
cation and a radical.
- Bonds break to give the most stable cation.
Alkanes
- Fragmentation often splits off simple alkyl groups:
Loss of methyl
•Loss of ethyl
•Loss of propyl
•Loss of butyl
M+ - 15
M+ - 29
M+ - 43
M+ - 57
-Branched alkanes tend to fragment forming the most stable
carbocation's.
32
35. Fragmentation Patterns
Aromatics:
-Fragment at the benzylic carbon, forming a resonance
stabilized benzylic carbocation .
(which rearranges to the tropylium ion)
H
H C Br
H
H
H C
H C
or
M+
35
37. Fragmentation Patterns
Alcohols :
-Fragment easily resulting in very small or missing parent ion
peak
-May lose hydroxyl radical or water
-M+ - 17 or M+ - 18
- Commonly lose an alkyl group attached to the carbinol
carbon forming an oxonium ion.
-1o alcohol usually has prominent peak at m/z = 31
corresponding to H2C=OH+
37
39. Fragmentation Patterns
Amines:
-Odd M+ (assuming an odd number of nitrogen are present)
−α-cleavage dominates forming an iminium ion
CH3CH2 CH2 N CH2 CH2CH2CH3
H
CH3CH2CH2N CH2
H
m/z =72
iminium ion
39
50. Alkanes
good M+
14-amu fragments
distinct M+
CH2=CH+
m/e = 41
CH2=CHCH2+
M-15, M-29, M-43, etc...
Alkenes
m/e = 27
loss of alkyl
strong M+
Cycloalkanes M-28
M-15, M-29, M-43, etc...
loss of CH2=CH2
loss of alkyl
strong M+
m/e = 105
C7H7+
C6H5+
m/e = 65 (weak)
C5H5+
M+ and M+2
Cl and Br
m/e = 49 or 51
Halides
m/e = 91
m/e = 77
Aromatics
C8H9+
CH2=Cl+
m/e = 93 or 95
CH2=Br+
M-36, M-38
loss of HCl
M-79, M-81
loss of Br·
51. M+ weak or absent
M-15, M-29, M-43, etc...
m/e = 31
CH2=OH+
m/e = 45, 59, 73, ...
RCH=OH+
m/e = 59, 73, 87, ...
R2C=OH+
M-18
loss of H2O
M-46
Alcohols
loss of alkyl
loss of H2O and CH2=CH2
strong M+
Phenols
strong M-1
loss of H·
M-28
loss of CO
M+ stronger than alcohols
M-31, M-45, M-59, etc...
loss of OR
CH2=OR+
M+ weak or absent
Amines
loss of alkyl
m/e = 45, 59, 73, ...
Ethers
M-15, M-29, M-43, etc...
Nitrogen rule
m/e = 30
CH2=NH2+ (base peak)
M-15, M-29, M-43, etc...
loss of alkyl
51
52. weak M+
m/e = 29
M-29
loss of HCO
M-43
loss of CH2=CHO
m/e = 44, 58, 72, 86, ...
McLafferty rearrangement
strong M+
aromatic aldehyde
M-1
Aldehydes
HCO+
aromatic aldehyde loss of H·
M+ intense
M-15, M-29, M-43, etc...
m/e = 43
CH3CO+
m/e = 55
+CH2CH=C=O
m/e = 42, 83
in cyclohexanone
m/e = 105, 120
Ketones
loss of alkyl
in aryl ketones
M+ weak but observable
M-17
M-45
Carboxylic Acids
loss of OH
loss of CO2H
m/e = 45
CO2H+
m/e = 60
·CH2C(OH)2+
M+ large
aromatic acids
52
53. M+ weak but observable
M-31
methyl esters loss of OCH3
m/e = 59
methyl esters CO2CH3+
m/e = 74
methyl esters
CH2C(OH)OCH3+
M+ weaker
Esters
methyl esters
higher esters
M-45, M-59, M-73, etc...
loss of OR
m/e = 73, 87, 101
CO2R+
m/e = 88, 102, 116
·CH2C(OH)OR+
m/e = 61, 75, 89
RC(OH)2+ (long alkyl ester)
m/e = 108
loss of CH2=C=O (benzyl,
acetate)
m/e = 105
C6H5CO+ (benzoate)
M-32, M-46, M-60
loss of ROH (ortho effect)
53
54. RA of Isotopes
RELATIVE ABUNDANCES OF ISOTOPES
Isotope peak : The isotope peak are obtained when a molecule
contains heavier isotope of certain atoms than the
common isotopes.
Commonly seen isotope peak are (M+1)+ peaks or
(M+2)+ peaks
Intensity of an isotope peak is much lesser than that of
the (M)+ peak except when Cl or Br is present in the
molecule.
54
55. ISOTOPES
Most elements occur naturally as a mixture of isotopes.
-The presence of significant amounts of heavier isotopes leads
to small peaks that have masses that are higher than the
parent ion peak.
M+1 = a peak that is one mass unit
higher than M+
M+2 = a peak that is two mass units
higher than M+
55
56. RA of Isotopes
RELATIVE ABUNDANCES OF ISOTOPES
intensity of an isotope peak depends on the relative
abundance of that isotope in nature.
The relative abundance of an isotope is calculate on
the basis of 100molecules.
From RA, the intensity of (M+1)+, (M+2)+ peaks can
be determined.
For a compound containing one carbon atom , out of
every 100 molecules, 98.892 molecule contain C12
isotope and 1.108 molecule contain C13 isotope
56
57. RA of Isotopes
RELATIVE ABUNDANCES OF ISOTOPES
Hence , the intensity of (M+1)+ peak is about 1.1% of
the intensity of the (M) +peak and the ratio of the
intensities of M+ and (M+1)+ peak is 98.892:1.108.
For compound containing silicon , the intensities of
(M) + peak corresponding to Si28 isotope , (M+1) + peak
corresponding to Si29 isotope and (M+2) + peak
corresponding to Si30 isotope are in proportion of their
relative abundance in the nature , i.e. 92.18:4.71:3.12.
57
58. RA of Isotopes
RELATIVE ABUNDANCES OF ISOTOPES
For compound containing sulphur , the ratio of
intensities of (M) +: (M+2) + peaks , corresponding to
S32 and S34 isotopes is 95.018:4.215.
The height of the peak is the measure of intensity of
that peak.
Fluorine and iodine have only one naturally occurring
isotope corresponding to atomic mass of 19 and 127,
resp.
Hence they produced only one peak corresponding to
(M) + ion.
58