Rearrangement

A complete Detail on Rearrangement which gives a broad idea about the topic

1. REARRANGEMENT Presented by : Arvind Singh Heer MSc-1 (Sem-2) Inorganic Chemistry MITHIBAI COLLEGE

2. CONTENT Introduction. Cope Rearrangement. Claisen Rearrangement. Curtius Rearrangement.

3. INTRODUCTION What is Rearrangement reaction? A rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule. In the example below the substituent R moves from carbon atom 1 to carbon atom 2:

4. Cope rearrangement The  Cope rearrangement  is an extensively studied  organic reaction  involving the  [3,3]- sigmatropic rearrangement  of 1,5-dienes. It was developed by  Arthur C. Cope For example 3-methyl-1,5-hexadiene heated to 300°C yields 1,5-heptadiene. The Cope rearrangement causes the fluxional states of the molecules in the  bullvalene  family

5. Mechanism of the Cope Rearrangement

6. Claisen rearrangement The  Claisen rearrangement  (not to be confused with the  Claisen condensation) is a powerful carbon-carbon bond-forming  chemical reaction  discovered by  Rainer Ludwig Claisen . The heating of an  allyl  vinyl ether  will initiate a  [3,3]- sigmatropic rearrangement  to give a γ,δ -unsaturated carbonyl. Discovered in 1912, the Claisen rearrangement is the first recorded example of a [3,3]- sigmatropic rearrangement.

7. General reaction Allyl vinyl ether Ortho- allyl phenol

8. Mechanism of the Claisen Rearrangement

9. Curtius Rearrangement The curtius  rearrangement is intramolecular . The optical activity of the migrating R group is never lost confirming that R is never free during the course of the rearrangement.  This reaction is very general reaction applicable to all carboxylic acids-aliphatic, alicyclic , hetero cyclic as well as aromatic. It gives good yield of isocyanate if water is absent. However, the reaction can be carried out in water or alcohol. Lewis acids or protic catalyze the reaction but these are unnecessary for good results.

10. Mechanism Acid azide isocyanate

11. REFERENCE March’s Advanced Organic Chemistry: Reactions, Mechanisms and Structure Michael B. Smith Jerry March ( SIXTH EDITION ) - THANK YOU