Transcript Alcohols and Carbonyls - Calderglen High School

Alcohols and Carbonyls
Ethanol. Alkanol family, Aldehydes
and Ketones. Methanol and
Methanal
Index
Ethanol
Homologous series CnH2n+1OH
Alcohol structures
Oxidation of alcohols
Aldehydes and Ketones
Methanol
Ethanol C2H5OH
H
H
C
H
H
Functional group -OH
Hydrogen bonding allows ethanol to dissolve
in water, pH 7. b.p. 78 oC.
C
H
This effect decreases in alcohols
OH Hydroxyl group as the length of the hydrocarbon chain increases
Ethanol is a good solvent, it behaves both
like water and other hydrocarbon
solvents.
R
O
H
+
+
H
O
-
H
Combustion of ethanol
CH3CH2OH + 3 O2
 2 CO 2 + 3 H2O
Ethanol can be used as a fuel in cars.
H = - 1367 kJ mol -1
+
Ethanol C2H5OH
Manufacture of Ethanol
1. Fermentation Fermentation is used to make all alcohol based drinks.
Any vegetable matter containing carbohydrates can be used.
yeast
C6H12O6  2CH3CH2OH + 2CO
2
2. Hydration of Ethene (Industrial manufacture of Ethanol)
C2H4 + H2O  CH3CH2OH
Cracking fractions from crude oil is a cheaper way to produce ethanol.
(more expensive than making petrol)
Reaction Conditions:
300oC , High Pressure 60 Atm. , phosphoric acid catalyst.
Uses of Ethanol
Drinks
Ethanol is a natural product of fermentation. Ethanol
cannot be more than 15% of the fermentation
mixture, as ethanol is a poison and will kill the yeast.
Solvent
In varnishes (as it evaporates easily), dyes, perfumes and
drugs.
Chemical
In the production of vinegar, ether, chloroform and
feedstock ethyl esters and ethene.
Fuel
Increasingly seen as an important fuel. Meths is ethanol
with added methanol. Cars can use ethanol as a fuel.
Others
In thermometers (cheaper and safer than Hg and
de-icers.
Dehydration of ethanol
Catalyst
CH3CH2OH
Ethanol

C2H4
+ H2O
Ethene
When hot ethanol is passed over aluminium oxide
ethene gas is produced.
Ethene is very a very important chemical, it is the basis
for many plastics. E.g. Polythene
Homologous Series CnH2n+1OH
Functional molecular structure
Methanol, CH3OH; Ethanol C2H5OH; Propanol C3H7OH
Straight chain isomers of Alkanols
Propanol C3H7OH, has 2 isomers, propan-1-ol and propan-2-ol.
H
H
H
H
C
C
C
H
H
H
propan-1-ol
OH
H
H
H
H
C
C
C
H
OH
H
propan-2-ol
H
H
H
H
H
H
C
C
C
C
H
CH3
H
OH
1. Decide on the type of
compound (ie. consider
functional group)
2. Select the longest chain
3. Name the compound
with the branched
chains in ascending
order.
Naming alcohols
H
alcohol (alkanol)
4 C’s  butanol
2-methylbutan-1-ol
Different types of alcohol
H
H
H
C
C
H
OH
C
H
H
C
C
O
H
C
C
C
H
H
C
Secondary alcohol,
2 C’s joined to the
C bonded to
the OH group
Primary alcohol,
1 C joined to the
C bonded to
the OH group
O
H
H
H
C
C
C
H
OH
H
propan-2-ol
Tertiary alcohol,
3 C’s joined to the
C bonded to
the OH group
CH3
H
CH3
C
CH3
OH
2-methylpropan-2-ol
Other Alcohols
1. Cycloalkanol
H
H
H
C
H
C
H
O
C
C
H
H
Cyclohexanol is a secondary alcohol
H
H
C
H
C
H
H
2. Diols (dihydric)
H
OH
OH
C
C
H
H
H
Ethane-1,2-diol
Anti freeze
3. Triols (Trihydric)
e.g. propane –1,2,3,triol or Glycerol is used in cosmetics, paints and
nitroglycerine explosives.
C=O carbonyl group
Oxidation of Alcohols
Primary alcohols can be oxidised in two stages,
1st Stage - Hydrogen is lost; 2nd Stage - oxygen is gained.
H
1st
R
C
O
oxidation
H
+
O
R
O
R
C
H
+
H2O
aldehyde
O H
2nd
C
H
aldehyde
+
O
oxidation
O
R
C
O
H
acid
Secondary alcohols can be oxidised to form ketones,
Tertiary alcohols do not undergo oxidation.
O
R
C
ketone
R1
CHO alkanal functional group
C=O ketone functional group
Aldehydes and Ketones
CH3
C=O
CH3
+ -
H
C=O
H
CH3
C=O
H
CH3CH2
CH3
C=O
Propanone, nail varnish remover and
is used in the making of perspex
Methanal, 40% in water is formalin,
and is used to make polymers
Ethanal, It’s trimer (CH3CHO)3 is used as a
sleep inducing drug. It also causes a hangover
Butanone, is a solvent used to make VHS tapes.
Butan-2-one
C4H8O
RSC video on silver mirror
Aldehydes and Ketones
Distinguishing tests
(Using mild oxidising agents.)
Aldehydes are oxidised to carboxylic acids
1. Fehlings solution contains Cu2+ ions (blue) which form Cu+ ion
(orange-red) in the presence of aldehydes.
2. Tollen’s reagent contains Ag+ ions, which form Ag in the presence
of aldehydes (silver mirror test)
3. Acidified Potassium Dichromate orange Cr2O72-(aq) to green Cr3(aq)
Ketones do not react with oxidising agents.
Methanol, Steam reforming
The steam used must be pure.
1. Coal
synthesis gas
1000 oC
Carbon
+
steam
2. Natural Gas (UK)
Methane
+ steam
 Carbon monoxide +
900 oC
Ni Catalyst
30 Atmos
hydrogen
synthesis gas
 Carbon monoxide +
hydrogen
Methanol is oxidised into methanal, either by:
1. Zinc/Chromium oxide catalysts 350-450oC and 200-300 Atm.
2. Cu/Zn/Al oxide catalysts 175-300oC and 40-100 Atm.
CH3OH
+
O2

HCHO + H20
Uses for Methanol and Methanal
Methanol
Fuel
Added to ethanol to make
meths, cleaner flame than
hydrocarbons.
Added to petrol octane
number 114. MTBE
(Methyl Tertiary Butyl
Ester)
Can be converted into
petrol using Zeolite.
Drugs and Fabrics
Methanal
Formalin,
preserve biological
specimens
Polymers
Polymethanal, machine
parts
Melamine, Electrical
insulators
Phenol methanal, heat
resistant are all
thermosettings plastics