1. TOPIC: OXIDATION

ASSIGNED BY:
DR.SAJID MEHMOOD

ASSIGNED TO:
01,02,04

AMNA , AZWAH AND SIDRA MARYUM

ORGANIC CHEMISTRY PAPER 2

2. PREPARED BY: AZWAH ALI
UNIVERSITY OF EDUCATION ,TOWNSHIP CAMPUS LAHORE

3. CONTENTS:

DEFINITION OF DEHYDROGENATION:

Aromatization of Six-Membered rings in presence of
hydrogenation catalysts.(Pt,S,Se or Quionones):

Dehydrogenations yielding Carbon-Carbon double Bonds:

Dehydrogenation of Alcohals to Aldehydes and Ketones:

Oxidation of Phenols and Aromatic Amines to Quinones:

Dehydrogenation of Amines:

Oxidation of Hydrazines,Hydrazones,and Hydroxylamines:

4. DEFINITION
“A chemical reaction involving elimination of hydrogen
from a compound to produce a less saturated analog”

5. Dehydrogenation reactions fall into six
classes
1.
Aromatization of Six-Membered rings in presence of hydrogenation
catalysts.(Pt,S,Se or Quionones)
2.
Dehydrogenations yielding Carbon-Carbon double Bonds
3.
Dehydrogenation of Alcohals to Aldehydes and Ketones
4.
Oxidation of Phenols and Aromatic Amines to Quinones
5.
Dehydrogenation of Amines
6.
Oxidation of Hydrazines,Hydrazones,and Hydroxylamines

6. 1. Aromatization of six membered
rings


Hexahydro-terelimination

7. Six membered alicyclic rings can be
aromatized in number of ways

1.
Six membered alicyclic rings can be aromatized in number of ways.
Hydrogenation catalysts such as palladium ,platinium,and nickel.
CYCLOHEXENE has been detected as an intermediate in the conversion
of CYCLOHEXANE to BENZENE,using Pt.
Pt
300-350
intermediate

8. 2.The elements SULPHUR and SELENIUM which
combine with hydrogen evolved to give
respectively H2S and HSe.
3.Quionones which become reduced to corresponding Hydroquinones.
Chloranil(2,3,5,6 tetrachloro-1,4-benzoquinone) and DDQ (2,3-dichloro-5,6dicyano-1,4-benzoquinone) are important quinones used for aromatizations.It
is likely that the mechanism involves a transfer of hydride to the quinone
oxygen,followed by the transfer of a proton to the phenolate ion
.

9. 2:Dehydrogenations yielding CarbonCarbon double Bonds

Dihydro-elimination
It is a synthesis developed by Leonard and Co.workers in which tertiary amines give Enamines
when treated with mercuric acetate,in this case the initial product is the iminium ion 1 which
loses a proton to give the enamines.

10. 2-In another example ,the oxidizing agent SeO2 can in certain
cases convert a carbonyl compound to an à,ß-unsaturated
carbonyl compound by removing H2.
The reaction has been most often applied in
Steroid series

11. 3:Dehydrogenation of Alcohals to
Aldehydes and Ketones
C,O-Dihydro-elimination
copper
RCHO
RCH2OH
chromite
RCHOHR
~
K2Cr2O7
H2SO4
RCOR`

12. Primary alcohals can be converted to aldehydes and
Secondary alcohals to ketones in seven main ways,whose
names are as following but explanation here is not of concern.

1.
Oppenauer oxidation

2.
With DMSO based reagents

3.
TEMPO and related reagents

4.
With hypervalent Iodine reagent

5.
By catalytic dehydrogenation

6.
Miscellaneous reagents

13. 4:Oxidation of Phenols and Aromatic Amines to
Quinones
1/O,6/O-Dihydroelimination:
O
OH
K2CrO7
H2SO4
OH
O
cyclohexa-2,5-diene-1,4-dione
hydroquinone Ortho and para diols are easily oxidized to Ortho- and para –
quinones respectively

14. Many oxidizing agents have been
used:

1.
Acid dichromate

2.
Silver oxide

3.
Silver carbonate

4.
Lead tetraacetate

5.
HIO4

6.
NBS_H2O_H2SO4

7.
MnO2 on bentonite with microwave irriadiation

8.
Dimethyl dioxarane

15. In below case,it seems to vary with the oxidizing agent.For
oxidation of catechol with NaIO4,it was found that the reaction
conducted in H2 18O gave unlabeled quinone,so the following
mechanism was proposed .
NaIO4
O
OH
O
OH
pyrocatechol
O
H
O
cyclohexa-3,5-diene-1,2-dione
2-hydroxyphenoxy diiodohypoiodite
I3O

16. 5:Dehydrogenation of Amines
1/1/N,2/2/C-Tetrahydrobielimination
RCH2NH2
RCN
Primary amines at a primary carbon can be dehydrogenated to
nitriles.The reaction has been carried out with a variety of reagents
among others.
1.
2.
3.
4.
5.
6.
Lead acetate
NaOCl
K2S2O8/NiSO4
Me3N/O/OsO4
Ru/Al2O3/O2
CuCl/O2/pyridine

17. 6:Oxidation of Hydrazines,Hydrazones,and
Hydroxylamines
1/N,2/N-Dihydroelimination
NH
N
NH
N
NaOBr
1,2-diphenylhydrazine
1,2-diphenyldiazene
N,N`-Diarylhydrazines(hydrazo compounds) are oxidized to azo
compounds by several oxidizing agents including
NaOBr,HgO,K3Fe(CN)6under phase transfer conditions or with
galvinoxyl.
Hydrazines (both alkyl and aryl) substituted on only one side also
give azo compounds ,but these are unstable and decompose to
nitrogen and the hydrocarbon

18. Hydrazines (both alkyl and aryl) substituted on only one side also
give azo compounds ,but these are unstable and decompose to
nitrogen and the hydrocarbon
H
NH
1-phenylhydrazine
NH2
N
NH
+
1-phenyldiazene
Benzene
N2

19. Hydrazones are oxidized with HgO,Ag2O,MnO2,lead acetate .or
certain other agents, Diazo compounds are obtained.
HgO
R2C
N
NH2
_
+
R2C
N
N
Aromatic hydroxylamine are easily oxidized to nitroso compounds
most commonly by acid dichromate.
NH
N
OH
Acid dichromate
N-hydroxybenzenamine
1-nitrosobenzene
O

20. Thank
you