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Rearrangement Rxns: Wagner–Meerwein, Favorskii, Claisen, Cope | Chemistry Optional Notes for UPSC PDF Download

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 Page 1


1
Rearrangement Reactions
? A reaction in which carbon skeleton or the functional group 
or both are modified is called rearrangement reaction.
? Migration of an atom or group from one center (migration 
origin) to another center (migration terminus) within the 
molecule is called rearrangement reaction
X
Y Z
X
Y Z
Migrating
Group
Migration 
Origin
Rearrangement
Migration 
terminus
Page 2


1
Rearrangement Reactions
? A reaction in which carbon skeleton or the functional group 
or both are modified is called rearrangement reaction.
? Migration of an atom or group from one center (migration 
origin) to another center (migration terminus) within the 
molecule is called rearrangement reaction
X
Y Z
X
Y Z
Migrating
Group
Migration 
Origin
Rearrangement
Migration 
terminus
2
Rearrangement Reactions
? In general migration take place from adjacent 
centre (1,2-shifts)
? Long range rearrangements are also possible
? Nucleophilic or anionotropic rearrangements: 
migrating group moves with its electron pair. 
? Electrophilic or cationotropic rearrangements : 
migrating group moves without electron pair. ( 
Fries rearrangement) 
? Free-radical rearrangements : migrating group 
moves with single electron.( photo fries 
rearrangement)
Page 3


1
Rearrangement Reactions
? A reaction in which carbon skeleton or the functional group 
or both are modified is called rearrangement reaction.
? Migration of an atom or group from one center (migration 
origin) to another center (migration terminus) within the 
molecule is called rearrangement reaction
X
Y Z
X
Y Z
Migrating
Group
Migration 
Origin
Rearrangement
Migration 
terminus
2
Rearrangement Reactions
? In general migration take place from adjacent 
centre (1,2-shifts)
? Long range rearrangements are also possible
? Nucleophilic or anionotropic rearrangements: 
migrating group moves with its electron pair. 
? Electrophilic or cationotropic rearrangements : 
migrating group moves without electron pair. ( 
Fries rearrangement) 
? Free-radical rearrangements : migrating group 
moves with single electron.( photo fries 
rearrangement)
3
Crossover Experiment
? Cross over experiment  is used to find out whether a 
rearrangement is intermolecular or Intramolecular.
? A mixture of two structurally related substrates, X- A- B 
and Y- C- Z are allowed to react and products after 
rearrangement were observed.
? If product is a mixture of four different species, the 
reaction is intermolecular. ( A-B-X, C-Z-Y , A-B-Y and C-Z-
X)
? If Product is a mixture of two species, then reaction is 
intramolecular. (A-B-X, C-Z-Y )
Page 4


1
Rearrangement Reactions
? A reaction in which carbon skeleton or the functional group 
or both are modified is called rearrangement reaction.
? Migration of an atom or group from one center (migration 
origin) to another center (migration terminus) within the 
molecule is called rearrangement reaction
X
Y Z
X
Y Z
Migrating
Group
Migration 
Origin
Rearrangement
Migration 
terminus
2
Rearrangement Reactions
? In general migration take place from adjacent 
centre (1,2-shifts)
? Long range rearrangements are also possible
? Nucleophilic or anionotropic rearrangements: 
migrating group moves with its electron pair. 
? Electrophilic or cationotropic rearrangements : 
migrating group moves without electron pair. ( 
Fries rearrangement) 
? Free-radical rearrangements : migrating group 
moves with single electron.( photo fries 
rearrangement)
3
Crossover Experiment
? Cross over experiment  is used to find out whether a 
rearrangement is intermolecular or Intramolecular.
? A mixture of two structurally related substrates, X- A- B 
and Y- C- Z are allowed to react and products after 
rearrangement were observed.
? If product is a mixture of four different species, the 
reaction is intermolecular. ( A-B-X, C-Z-Y , A-B-Y and C-Z-
X)
? If Product is a mixture of two species, then reaction is 
intramolecular. (A-B-X, C-Z-Y )
4
Crossover Experiment
X
A B
Y
C
Z
X A B
Y
C
Z
Intramolecular
X
A B
Y
C
Z
X A B
Y
C
Z
X
A B
Y
C
Z
Intermolecular
Page 5


1
Rearrangement Reactions
? A reaction in which carbon skeleton or the functional group 
or both are modified is called rearrangement reaction.
? Migration of an atom or group from one center (migration 
origin) to another center (migration terminus) within the 
molecule is called rearrangement reaction
X
Y Z
X
Y Z
Migrating
Group
Migration 
Origin
Rearrangement
Migration 
terminus
2
Rearrangement Reactions
? In general migration take place from adjacent 
centre (1,2-shifts)
? Long range rearrangements are also possible
? Nucleophilic or anionotropic rearrangements: 
migrating group moves with its electron pair. 
? Electrophilic or cationotropic rearrangements : 
migrating group moves without electron pair. ( 
Fries rearrangement) 
? Free-radical rearrangements : migrating group 
moves with single electron.( photo fries 
rearrangement)
3
Crossover Experiment
? Cross over experiment  is used to find out whether a 
rearrangement is intermolecular or Intramolecular.
? A mixture of two structurally related substrates, X- A- B 
and Y- C- Z are allowed to react and products after 
rearrangement were observed.
? If product is a mixture of four different species, the 
reaction is intermolecular. ( A-B-X, C-Z-Y , A-B-Y and C-Z-
X)
? If Product is a mixture of two species, then reaction is 
intramolecular. (A-B-X, C-Z-Y )
4
Crossover Experiment
X
A B
Y
C
Z
X A B
Y
C
Z
Intramolecular
X
A B
Y
C
Z
X A B
Y
C
Z
X
A B
Y
C
Z
Intermolecular
5
Types of Rearrangement Reactions
A) 1,2 rearrangement reaction
B) Pericyclic Reactions
C) Olefin metathesis
Read More
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FAQs on Rearrangement Rxns: Wagner–Meerwein, Favorskii, Claisen, Cope - Chemistry Optional Notes for UPSC

1. What are rearrangement reactions?
Ans. Rearrangement reactions are organic reactions in which the connectivity of atoms within a molecule is changed, resulting in the rearrangement of the molecular structure. These reactions involve the migration of functional groups or atoms within the molecule, leading to the formation of new bonds and the rearrangement of existing bonds.
2. What is the Wagner-Meerwein rearrangement?
Ans. The Wagner-Meerwein rearrangement is a type of rearrangement reaction in organic chemistry. It involves the migration of alkyl or aryl groups from one carbon atom to an adjacent carbon atom in a carbocation intermediate. This rearrangement can result in the formation of different isomeric products.
3. How does the Favorskii rearrangement work?
Ans. The Favorskii rearrangement is a rearrangement reaction that involves the migration of a carbonyl group (C=O) from one carbon atom to an adjacent carbon atom. This reaction typically occurs under basic conditions and results in the formation of an α-halo ketone or α-halo carboxylic acid, depending on the starting material.
4. What is the Claisen rearrangement?
Ans. The Claisen rearrangement is a rearrangement reaction that involves the migration of an alkyl or aryl group from one carbon atom to an adjacent carbon atom in an allyl vinyl ether or an allyl vinyl ester. This reaction typically occurs under basic conditions and leads to the formation of a β-keto ester or a β-keto ether, respectively.
5. How does the Cope rearrangement work?
Ans. The Cope rearrangement is a rearrangement reaction in which a 1,5-diene undergoes a [3,3]-sigmatropic rearrangement. This reaction involves the migration of a π-bond from one carbon-carbon double bond to an adjacent double bond. The Cope rearrangement is typically thermally driven and results in the formation of a new carbon-carbon double bond in a different position within the molecule.
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