beckmann rearrangement , mechanisms with different catalysts,stereochemistry and applications

1. Beckmann
Rearrangement
PRESENTED BY:
MAHROOSH
ABBASI

3. Rearrangement:
When carbon
skeleton of
the molecule
is rearranged
to give a
structural
isomer of
original
molecule
Migration of
group from
one to
another
atom either
within same
molecule or
to another
molecule
definitions

4. Radical
rearrangements
Nucleophillic
rearrangements
Electrophillic
rearrangements
Types of
rearrangements

5. Beckmann rearrangement:
History:
Ernst Beckmann
Definition:
“The acid catalyzed conversion
of Oximes to N-substituted Amides is
called Beckmann rearrangement’’

6. General reaction:
Ketone Oxime Amides

7. Aldehyde
Hydroxyl
Amine
Aldoxime
Ketone
Hydroxyl
Amine
Ketoxime

8. Aliphatic
oximes
Aliphatic
Amides
Cyclic
oximes
Cyclic
amides

9. Reactant and Product:
Ph
H
N
H
N
NOH
NOH
NOH H
N
O
O
O
Ph

10. H2SO4
PCl5
HClH3PO
4
SiO2
Catalysts

11. How to form Oxime:

12. Stereoselect
-ive
Concerted
Group ANTI
to l.g
migrates
Retention
of
configurati
on of M.G
Stereochemistry:

13. Migratory aptitude:
H Ph 3˚C 2˚C 1˚C
≫ > > >

14. Mechanism with Acid:
+H
+
+
H2O _R
H2O
H
+
H
+
←←
Oxime Oxonium ion
+
+
N-Subs Amides
+ +
=
→
Tautomerize
-

15. Mechanism with PCl5:
-H
–OPCl4
H2O

16. Chiral migrating group:

17. EWG with migrating group:

18. Applications
Caprolactam
Isoquinoline
Paracetamol

19. Formation of NYLON:
BaseH2SO4
Mechanism
N-hydroxylamines Caprolactam Nylon

20. Formation of Isoquinoline:

21. s