Transcript + [O] - MrFisherChemistry

AS Chemistry
OXIDATION OF ALCOHOLS
OXIDATION OF ALCOHOLS
Oxidised to aldehydes and acids or ketones
NOT
SIGNIFICANT
for TERTIARY
alcohols!
for PRIMARY
alcohols
-CH2OH
for SECONDARY
alcohols
-C-CH(OH)-C-
NB Oxidant = hot acidified Cr2O72- [dichromate(VI)] ion]
Provided by mixture of potassium dichromate(VI),
K2Cr2O7, and excess dilute sulphuric acid, H2SO4.
Oxidant is represented by : [O]
Orange Cr2O72- reduced to green Cr3+
PRIMARY
SECONDARY
C
H
C
C
C
C
H
OH
 + [O]
H
C
+ H2O
Aldehyde
O
 + [O]
OH
C
Acid
C
H
C
OH
 + [O]
C
TERTIARY
C
O
C
C
C
C
C
OH
 + [O]
NO SIGNIFICANT
OXIDATION
+ H2O
Ketone O
 + [O]
NO FURTHER
OXIDATION
- no C – H bond
- no C–H bond
Any oxidation
that does
occur involves
breaking C-C
bonds  loss
of original
structure.
What are the oxidation products of :
1. Ethanol?
2. Methyl-propan-2-ol? 3. Butan-2-ol ?
CH3CH2OH
CH3C(CH3)(OH)CH3
Primary
Tertiary
Secondary
1. CH3CH2OH + [O]  CH3CHO + H2O
CH3CHO + [O]
 CH3COOH
CH3CH2CH(OH)CH3
Ethanal
Ethanoic acid
2. No significant oxidation
3. CH3CH2CH(OH)CH3 + [O]  CH3CH2COCH3 + H2O
Butanone
Controlling Oxidation Products
To Maximise the
Production of an
ALDEHYDE
To Maximise the
Production of an ACID or a
KETONE
This is PARTIAL oxidation
This is FURTHER oxidation
Use only molar proportions of
dichromate and acid
Use excess of dichromate
and acid
Use minimum contact time
between alcohol and oxidant
by use of immediate distillation
Use maximum contact time
between alcohol and oxidant by
use of reflux
Add acidified dichromate to
the alcohol to avoid the
presence of excess oxidant
Pre-mix acidified dichromate
and alcohol to ensure excess
oxidant at all times
Click here for Distillation and Reflux Apparatus
Click on the options to select the possible oxidation
products (MAY BE MORE THAN ONE) derived from :
Methanal
Methanoic acid
Methanone
None
Propanal
Propanoic acid
Propanone
None
Propanal
Propanoic acid
Propanone
None
Pentan-3-al
Pentan-3-oic acid Pentan-3-one
None
2-Methylbutanal
2-Methylbutanoic
acid
None
Methanol
Propan-2-ol
Propan-1-ol
Pentan-3-ol
2-Methylbutan-2-ol
2-Methylbutanone
The End
Distillation
Reflux