The document discusses the McLafferty rearrangement, which is a reaction observed using mass spectrometry. The rearrangement involves a carbonyl compound undergoing cleavage of alpha and gamma bonds, resulting in an enol radical cation and a neutral alkene fragment. Fred McLafferty first observed this reaction using mass spectrometry. The reaction proceeds through a six-membered ring transition state and has specific requirements for the carbonyl compound. Examples of compounds undergoing the rearrangement include 2-hexanone and hexanoic acid.
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
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.
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 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
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.
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 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
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2. What is McLafferty Rearrangement?
Mass spectroscopy is a technique used to determine the mass of a given molecule.
The molecule is placed inside the spectrometer and ionized by high-energy electrons.
After the molecules are ionized, they become radical cations that can then be sorted and weighed.
When hydrogen is available at the gamma position on carbonyl compounds, these compounds go through a
specific rearrangement due to the cleavage of multiple bonds, including the bonds at alpha and gamma positions.
This reaction is known as the McLafferty rearrangement.
Fred Warren McLafferty was an American chemist known for his work in mass spectrometry.
He is best known for the McLafferty rearrangement reaction that was observed with mass
spectrometry.
3. The rearrangement involves a six-membered ring transition state in which the carbonyl group pulls off
the gamma proton, splitting the molecule into two pieces.
These pieces consist of an enol radical cation and a neutral alkene fragment.
𝝅 𝐞𝐥𝐞𝐜𝐭𝐫𝐨𝐧𝐬
n electrons
𝜸 𝐩𝐫𝐨𝐭𝐨𝐧𝐬
Requirements for McLafferty Rearrangement
Carbonyl compound Ethene Enol radical cation
4. MECHANISM OF McLAFFERTY REARRANGEMENT
STEP 𝟏
STEP 𝟐
Carbonyl compound
Enol radical cation tautomers
NOTE
Y can be H,R,OH,OR or NR2
5. STEP 𝟑
Ethene
Fragmented ion
Examples
2-Hexanone Propene
Acetone enol
radical cation
Hexanoic acid 1-Butene
Acetic acid enol
radical cation
APPLICATION
An application of this rearrangement
is in structural elucidation using mass
spectroscopy as the tool.
