McLafferty Rearrangement.pptx

Rearrangement reaction

1. McLafferty Rearrangement GUNASEELAN R 21CHE15

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 . n electrons   Requirements for McLafferty Rearrangement Carbonyl compound Ethene Enol radical cation

4. MECHANISM OF McLAFFERTY REARRANGEMENT STEP   STEP   Carbonyl compound Enol radical cation tautomers NOTE Y can be H,R,OH,OR or NR 2

5. STEP   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.