CHAPTER 18 ALCOHOLS/PHENOLS/ETHERS
ALCOHOLS
Definition: Organic compounds in which a hydroxyl group (OH) is attached to an aliphatic
carbon atom are called “Alcohols”. The functional group of alcohols is OH and the general
formula is R___OH or CnH2n+1OH. For example, methyl alcohol (CH3OH) etc.
Classification
Alcohols can be classified as;
Monohydric alcohols
Alcohols having one hydroxyl group (OH) are called “monohydric alcohols”.
Dihydric alcohols
Alcohols having two hydroxyl groups (OH) are called “dihydric alcohols”.
Trihydric alcohols
Alcohols having three hydroxyl groups (OH) are called “trihydric alcohols”. For example,
Primary alcohols
When the OH group is directly attached to the primary carbon, this is called “primary
alcohols”.
Secondary alcohols
When the OH group is directly attached to the secondary carbon, this is called “secondary
alcohols”.
Tertiary alcohols
When the OH group is directly attached to the tertiary carbon, this is called “tertiary
alcohols”.
, 10 alcohol 20 alcohol 30 alcohol
Nomenclature of alcohols
Common system
Alcohols are named as “Alkyl alcohols”. Typical examples of common names of alcohols
are;
IUPAC system
1. Select the longest continuous carbon chain having OH group.
2. Number this longest carbon chain starting 1 from that end nearer to the OH group.
3. Indicate the positions of the other groups if attached. When there are more than one
groups and groups are different, they are named alphabetically. A B C D E F G etc.
4. When there are more than one OH group, they are named as mono for one, di for two
and tri for three etc.
5. If the number of carbon atoms having OH group is the same form either side, then
number the chain from that end which is heavily substituted.
6. If more than one OH group are attached to the same carbon atom, the number of that
carbon atom is repeated.
7. IUPAC names of alcohols are named as “Alkanols”.
, Physical properties of Alcohols
1. Lower alcohols are colourless toxic liquids.
2. They have characteristic smell.
3. They have higher melting points and boiling points than alkanes.
4. They have hydrogen bonding.
5. They are soluble in water due to hydrogen bonding.
Structure of Alcohols
ALCOHOLS
Definition: Organic compounds in which a hydroxyl group (OH) is attached to an aliphatic
carbon atom are called “Alcohols”. The functional group of alcohols is OH and the general
formula is R___OH or CnH2n+1OH. For example, methyl alcohol (CH3OH) etc.
Classification
Alcohols can be classified as;
Monohydric alcohols
Alcohols having one hydroxyl group (OH) are called “monohydric alcohols”.
Dihydric alcohols
Alcohols having two hydroxyl groups (OH) are called “dihydric alcohols”.
Trihydric alcohols
Alcohols having three hydroxyl groups (OH) are called “trihydric alcohols”. For example,
Primary alcohols
When the OH group is directly attached to the primary carbon, this is called “primary
alcohols”.
Secondary alcohols
When the OH group is directly attached to the secondary carbon, this is called “secondary
alcohols”.
Tertiary alcohols
When the OH group is directly attached to the tertiary carbon, this is called “tertiary
alcohols”.
, 10 alcohol 20 alcohol 30 alcohol
Nomenclature of alcohols
Common system
Alcohols are named as “Alkyl alcohols”. Typical examples of common names of alcohols
are;
IUPAC system
1. Select the longest continuous carbon chain having OH group.
2. Number this longest carbon chain starting 1 from that end nearer to the OH group.
3. Indicate the positions of the other groups if attached. When there are more than one
groups and groups are different, they are named alphabetically. A B C D E F G etc.
4. When there are more than one OH group, they are named as mono for one, di for two
and tri for three etc.
5. If the number of carbon atoms having OH group is the same form either side, then
number the chain from that end which is heavily substituted.
6. If more than one OH group are attached to the same carbon atom, the number of that
carbon atom is repeated.
7. IUPAC names of alcohols are named as “Alkanols”.
, Physical properties of Alcohols
1. Lower alcohols are colourless toxic liquids.
2. They have characteristic smell.
3. They have higher melting points and boiling points than alkanes.
4. They have hydrogen bonding.
5. They are soluble in water due to hydrogen bonding.
Structure of Alcohols
