The document discusses the pinacol-pinacolone rearrangement, a chemical process that converts vicinal diols into carbonyl compounds through an acid-catalyzed mechanism involving protonation, dehydration, rearrangement, and dehydrogenation. Key aspects include its synthetic applications in creating spiro compounds, cyclic ketones, and carbonyls from alkenes, as well as its significance in the production of pharmaceuticals and pesticides. The document emphasizes the importance of migratory aptitude and the role of various leaving groups in enhancing the rearrangement process.

1. PINACOL-PINACOLONE
REARRANGEMENT
Presented By
Ranjit kumar Naik
CH/17/23
M.Sc.3rd
semester
Dept. Of Chemistry
Fakir Mohan University,Balasore

2. CONTENTS
 Introduction
 Rearrangement and its Mechanisms
 Characteristics
 Migratory Aptitude
 Synthetic Application
 Semipinacol Rearrangement
 Application
 conclusion

3. INTRODUCTION
The pinacol-pinacolone rearrangement was first
discovered by German Chemist William Rudolph
Fitting in the year 1859.
This rearragement got its name from classical example
of conversion of pinacol to pinacolone.
Pinacol(2,3-dimethyl-2,3-butanediol) is a vicinal diol,
which rearranged to produce 3,3-dimethyl-2-butanone,
commonly called as pinacolone.

4. PINACOL:
pinacol is completely substituted 1,2-diol .
pinacol is a solid organic compound which is white in
colour.
PINACOLONE:
Pinacolone is a very important ketone.
It has a camphor like odour and appears
to be a colourless liquid.

5. 
PINACOL-PINACOLONE REARRANGEMENT:
Pinacol-pinacolone rearrangement is a very
important process for the conversion of 1,2-
diol(vicinal diol) into carbonyl compound like
ketone or aldehyde in the presence of acid. It is
also known as acid catalysed reaction.

6. MECHANISM:
The pinacol pinacolone rearrangement
mechanism involve four steps .
 Step 1: Protonation
 Step 2: Dehydration
 Step 3: Rearrangement
 Step 4: Dehydrogenation

8. CHARACTERISTICS:
Anionotropic rearrangement carbon to
electron deficient carbon migration.
Electron donating groups attached to
migrating group increase the rate of reaction .
Mineral acids like H2SO4,HCl,HBr etc. are
used.
Elimination of water without
rearrangement can be achieved under drastic
condition.

9. MIGRATORY APTITUDE
The group with more electron donation has
greater migratory aptitude. The ease of migration
of different group in order: H>>Aryl>>Alkyl

10. MIGRATORY APTITUDE:
 The migratory aptitude of the alkyl group
with a longer chain is greater .
Pr- > Et- > Me
 Ethyl migrates faster than methyl because it
give more hyper conjugating stable
carbocation than methyl.
 The migratory aptitude of iso-propyl is greater
than n-propyl.

12. EXAMPLE:

13. SYNTHETIC APPLICATIONS
Synthesis of spiro compound:
 This rearrangement provides a synthetic
route
for the synthesis of spiro compound.

14. Synthesis of carbonyl compounds from alkenes:
 Isobutylaldehyde may be prepared from
isobutylene.

15. Cyclic ketones from cyclic diols:
 It is used to prepare cyclic ketones which
are otherwise very difficult to synthesize .
 Many sterically hindered ketones can be
produced by this rearrangement.

16. SEMI PINACOL-PINACOLONE
REARRANGEMENT:
 In semi pinacol-pinacolone rearrangement, one
hydroxy group must be present in the substrate
along with the other good leaving groups such as
– N2,-OTs,
-X etc.
 Semi pinacol rearrangement is more
regioselective than pinacol rearrangement.

17. TOSYL AS LEAVING GROUP:
 In this rearrangement, a less hindered hydroxy
group is converted to tosylate group(-OTs) which
easily leaves forming a carbocation.
 This carbocation rearranges to give a ketone and
ring expansion occurs.
 Tosyl is a bulky group and replaces the hydrogen
of the hydroxy group,which is not sterically
hindered.

18. TIFFENEAV-DEMJANOV
REARRANGEMENT:
 When amino alcohol is treated with HNO2 ,
amino group is converted into a diazonium
group.
 Nitrogen is the best leaving group and leaves to
form a carbocation which is then rearranged to
give a ketone.

19. EXAMPLES:
Ring contraction: 2-aminocyclohexanol is
converted into cyclopentanal in the presence of
nitrous acid.
Ring expansion: 1-aminoethylcyclohexanol is
converted into cyclohectanone in the presence of
nitrous acid.

20. DEHALOGENATION OF HALOALCOHOL:
 Haloalcohol or hydroxy halide is treated with
AgNO3 in an aqueous medium .
 AgX is precipitated and settled down leaving
behind a carbocation.
 Halides e.g – Cl and –Br are good leaving groups.

21. SYNTHETIC APPLICATION:
 Semi pinacol-pinacolone rearrangement is used in
synthesis of 7 and 8 membered rings. Cyclohexanone
can be converted into cycloheptanone in good yield.

22. APPLICATIONS:
 Synthesis of pesticides.
 Production of ketone.
 Synthesis of carbonyl compounds from
alkenes.
 Production of triadimefon, an antimycotic
agent that controls fungal diseases in
crops.
 Pinacolone is used in the production of
stiripentol and also used in the production
of stilbestrol pinacolone, a non –steroidal
steroid medication.

23. CONCLUSION:
 The pinacol- pinacolone rearrangement is
used in the preparation of many carbonyl
compounds. Thus , it is widely used in the
pharmaceutical industry and the creation of
pesticides and fungicides.