Organic Chemistry
The Alcohols
Leaving Certificate Chemistry
The alcohols are a group of organic
compounds in which one (or more) of the
hydrogen atoms of an alkane have been
replaced by an –OH hydroxyl group.
The First 4 Alcohols
Structural Formulae
Methanol: CH3OH
1 CarbonLong
-OH Group
present
H
H
C
H
OH
The First 4 Alcohols
Structural Formulae
Ethanol: C2H5OH
-OH Group
Other Uses
2 Carbon
Longest
Chain
C6H12O6
Glucose
Present
H
H
C
H
2C2H5OH + 2 CO2
C
OH
Ethanol
Produced in industry
by
fermentation
H
H
Fuel
Solvent Thermometer
The First 4 Alcohols
Structural Formulae
Propanol: C3H7OH
3 Carbon
Longest
Chain
-OH Group
Present
H
H
H
H
C
C
H
C
H
H
H
OH
The First 4 Alcohols
Structural Formulae
Butanol: C4H9OH
4 Carbon
Longest
Chain
H
-OH Group
Ptresent
H
H
H
H
C
C
C
C
H
H
H
H
OH
Primary & Secondary Alcohols
A primary
secondary
alcohol
alcohol
is an
is alcohol
an alcohol
in which
in which
the
carbon
the
carbon
atom
atom
that
that
is isbonded
bondedtoto the
the –OH
(hydroxyl) group
groupis is
itself
itself
alsoalso
bonded
bonded
to ONE
to
other other
TWO
carbon
carbon
atom atoms.
H
H
H
H Propan-2-ol
Propan-1-ol
C
C
C
H
H
OH
H
H
OH
Physical
Properties of
the Alcohols
Would you expect alcohols to
have higher boiling points than
alkanes/ Why?
Comparing the boiling points of the alkanes
and the alcohols
Alcohols
2006 Q. 10 (c)
450
119 K
400
300
250
200
226.5 K
350
Liquid
Gas
150
100
50
1
2
3
4
Number of Carbons
Boiling point in Kelvins
Alkanes
Why does each alcohol have a higher
boiling point than its corresponding alkane?
Each alcohol has a higher relative
molecular mass than its corresponding
alkane
2006 Q. 10 (c) (7)
Alcohols have strong
intermolecular hydrogen bonding
forces whereas alkanes are
influenced by much weaker Van Der
Waals forces.
H
H
C
∂—
O
H
∂+
H
H
O
H
C
H
H
Why is the difference in boiling points between methane
and methanol 226.5 K whilst the difference in boiling points
between butane and butanol is only 119 K?
Because the strength of the hydrogen
bonding is much weaker in butanol than it
is in methanol
2006 Q. 10 (c) (6)
This helps to explain why butanol is
virtually insoluble (slightly soluble) in water
whereas methanol is very soluble in water
• Would you expect all members of the
alcohol
family
be equallyalcohols
soluble in
Would
youtoexpect
water? Why?
to
be soluble in water/ Why?
Chemical
Reactions of
the Alcohols
Combustion
Combustion
CH3OH
Methanol
C2H5OH
Ethanol
1½O2
Oxygen
3 O2
Oxygen
CO2
2 H 2O
Carbon
Dioxide
Water
2 CO2
3 H 2O
Carbon
Dioxide
Water
Chemical
Reactions of
the Alcohols
Elimination
Dehydration (elimination)
H
H
H
H
C
H
C
H
C
H
Ethanol
C
OH
Aluminium Oxide H
[catalyst]
Al2O3
This is an elimination reaction
1. Formation of a saturated
compound
2. Loss of a small molecule
like water
H
Ethene
H2O
Water
2007 Q. 8 (a) (6)
Elimination reactions of alcohols
• Draw the structural formulas and name
the products of an elimination reaction to
1. Propanol
2. Butanol
Dehydration (elimination)
Propanol
H
H
H
H
C
C
C
H
H
H
OH
Aluminium
H
H
C
C
C
Oxide
C
H2O
Water
H
H
H
Propene
Dehydration (elimination)
Butanol
H
H
H
H
H
C
C
C
C
H
H
H
H
H
H
C
C
H
C
C
OH
Aluminium
Oxide
H
H2O
Water
H
H
H
H
Butene
Chemical
Reactions of
the Alcohols
Oxidation
Oxidation of a primary alcohol
Methanol CH3OH
H
H
C
O
Acidified Sodium
Dichromate
OH
H
C
C
Methanal
HCHO
O
H
H
OH
Methanoic Acid
HCOOH
Excess
H
Oxidation of a primary alcohol
Ethanol C2H5OH
H
H
H
C
C
H
H
O
H
H
C
H
C
Acidified Sodium
Dichromate
OH
OH
Excess
Ethanoic Acid
CH3COOH
H
H
O
C
C
H
Ethanal
CH3CHO
H
Oxidation of a primary alcohol
H
H
H
OH
H
C
C
C
H
H
H
Propanoic
Propanol
Propanal
Acid
C2CH23H
OH
5COOH
57CHO
O
OH
Acidified Sodium
Dichromate
Excess
Oxidation of a primary alcohol
H
H
H
H
H
OH
C
C
C
C
H
H
H
H
O
OH
Butanoic
Butanol
Butanal Acid
On reaction with acidified
sodium dichromate
In Excess
The Alcohols
Ethanol C2H5OH
Acidified sodium
dichromate
Hydrogen,
Nickel catalyst
Oxidation
Reduction
The Aldehydes
Ethanal CH3CHO
Acidified sodium
Reduction
dichromate
Hydrogen,
Oxidation
Nickel catalyst
The Carboxylic
Acids
Ethanoic Acid
CH3COOH
Oxidation of a secondary alcohol
H
H
O
OH
H
C
C
C
H
H
H
H
Acidified Sodium
Dichromate
Propanone
Propan-2-ol
Oxidation of a secondary
alcohol produces a ketone
Nail Varnish
Remover
Oxidation of a secondary alcohol
H
H
O
OH
H
H
C
C
C
C
H
H
H
H
Butanone
Butan-2-ol
Oxidation of a secondary
alcohol produces a ketone
H
Acidified
Sodium
Dichromate
Oxidation of a secondary alcohol
Acidified sodium dichromate The
The Alcohols
Ethanol C2H5OH
Hydrogen,
Nickel catalyst
Ketones
Propanone from
propan-2-ol
Acidified sodium
dichromate
Oxidation
H2, Ni Reduction
Reduction
The Aldehydes
Ethanal CH3CHO
Acidified sodium
Reduction
dichromate
Hydrogen,
Oxidation
Nickel catalyst
The Carboxylic
Acids
Ethanoic Acid
CH3COOH
Chemical
Reactions of
the Alcohols
The reaction of
ethanol with sodium
Reaction of ethanol with sodium
H
H
H
C
C
H
H
Na
2
O
Hydrogen
Sodium
H
Sodium
Ethoxide
Ethanol
C2H5OH
Na
Ethanol
Sodium
C2H5ONa
Sodium
Ethoxide
½ H2
Hydrogen
Chemical
Reactions of
the Alcohols
Reaction with an acid
(formation of an ester)
Esterification
H
H
O
C
C
O
H
Ethanoic Acid
CH3COOH
H
H
Ethyl Group
Ethyl Ethanoate
CH3COOC2H5
H
CH3COOH H
CH3COOC2H5
O
C
C2H5OH
H
C
H
H
H2SO4
Ethanol
O
CH
H
2
2 5OH
Esterification
H
H
H
O
C
C
C
H
Propanoic Acid
C2H5COOH
H
H
O
Methyl Group
Methyl Propanoate
H C2H5COOCH3
H
O
C
H
H
H2O
Methanol
CH3OH
Substitution
using UV Light
The Alkanes
Ethane C2H6
+ H2
- H2
The Chloroalkanes
Chloroethane C2H5Cl
The Alkenes
+ HCl , + Cl2
Ethene C2H4
+ H2O
- H2O Aluminium Oxide
Catalyst
The Polymers
Polythene & Polypropene
The Alcohols
Ethanol C2H5OH