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

 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