1. AN INTRODUCTION TO
THE CHEMISTRY
OF ALCOHOLS

2. THE CHEMISTRY OF ALCOHOLS
CONTENTS
Structure of alcohols
Nomenclature
Isomerism
Physical properties

3. THE CHEMISTRY OF ALCOHOLS Before you start it would be helpful to…
Recall the definition of a covalent bond
Recall the difference types of physical bonding
Be able to balance simple equations
Be able to write out structures for simple organic molecules
Understand the IUPAC nomenclature rules for simple organic compounds
Recall the chemical properties of alkanes and alkenes

4. CLASSIFICATION OF ALCOHOLS
Aliphatic • general formula CnH2n+1OH - provided there are no rings
• the OH replaces an H in a basic hydrocarbon skeleton

5. CLASSIFICATION OF ALCOHOLS
Aliphatic • general formula CnH2n+1OH - provided there are no rings
• the OH replaces an H in a basic hydrocarbon skeleton
PRIMARY 1° SECONDARY 2° TERTIARY 3°

6. Alcohols are named according to standard IUPAC rules
NAMING ALCOHOLS
Alcohols are named according to standard IUPAC rules
• select the longest chain of C atoms containing the O-H group;
• remove the e and add ol after the basic name
• number the chain starting from the end nearer the O-H group
• the number is placed after the an and before the ol ... e.g butan-2-ol
• as in alkanes, prefix with alkyl substituents
• side chain positions are based on the number allocated to the O-H group
e.g. CH3 - CH(CH3) - CH2 - CH2 - CH(OH) - CH3 is called 5-methylhexan-2-ol

7. STRUCTURAL ISOMERISM IN ALCOHOLS
Different structures are possible due to...
A Different positions for the OH group and
B Branching of the carbon chain
butan-1-ol
butan-2-ol
2-methylpropan-2-ol
2-methylpropan-1-ol

8. BOILING POINTS OF ALCOHOLS
Increases with molecular size due to increased van der Waals’ forces.
Alcohols have higher boiling points than
similar molecular mass alkanes
This is due to the added presence of
inter-molecular hydrogen bonding.
More energy is required to separate the molecules.
Mr bp / °C
propane C3H just van der Waals’ forces
ethanol C2H5OH van der Waals’ forces + hydrogen bonding

9. BOILING POINTS OF ALCOHOLS
Increases with molecular size due to increased van der Waals’ forces.
Alcohols have higher boiling points than
similar molecular mass alkanes
This is due to the added presence of
inter-molecular hydrogen bonding.
More energy is required to separate the molecules.
Mr bp / °C
propane C3H just van der Waals’ forces
ethanol C2H5OH van der Waals’ forces + hydrogen bonding
Boiling point is higher for “straight” chain isomers.
bp / °C
butan-1-ol CH3CH2CH2CH2OH 118
butan-2-ol CH3CH2CH(OH)CH3 100
2-methylpropan-2-ol (CH3)3COH
Greater branching =
lower inter-molecular forces

10. BOILING POINTS OF ALCOHOLS
Increases with molecular size due to increased van der Waals’ forces.
Alcohols have higher boiling points than
similar molecular mass alkanes
This is due to the added presence of
inter-molecular hydrogen bonding.
More energy is required to separate the molecules.
Mr bp / °C
propane C3H just van der Waals’ forces
ethanol C2H5OH van der Waals’ forces + hydrogen bonding
Boiling point is higher for “straight” chain isomers.
bp / °C
butan-1-ol CH3CH2CH2CH2OH 118
butan-2-ol CH3CH2CH(OH)CH3 100
2-methylpropan-2-ol (CH3)3COH
Greater branching =
lower inter-molecular forces

11. SOLVENT PROPERTIES OF ALCOHOLS
Solubility Low molecular mass alcohols are miscible with water
Due to hydrogen bonding between the two molecules
Heavier alcohols are less miscible
Solvent
properties Alcohols are themselves very good solvents
They dissolve a large number of organic molecules