Alcohols

Alcohols

Methanol CH3OH

Ethanol C2H5OH

Propan-1-ol C3H7OH

Propan-2-ol C3H7OH

Butan-1-ol C4H9OH

Butan-2-ol C4H9OH

Methanol CH3OH

Ethanol C2H5OH

Propan-1-ol C3H7OH

Butan-1-ol C4H9OH

Propan-2-ol CH3CH(OH)CH3

Butan-2-ol CH3CH(OH)C3H7

Classification of alcohols

1. Primary alcohol: contains one carbon atom directly attached to the carbon that contains the hydroxyl group, e.g. propan-1-ol

2. Secondary alcohol: contains two carbon atoms directly attached to the carbon that contains the hydroxyl group, e.g. propan-2-ol

Physical properties

Physical state: Liquid Boiling points much higher than the

corresponding alkanes, due to polar OH group

Physical properties

Solubility of methanol in (i) cyclohexane – not very soluble

methanol is polar cyclohexane is not (ii) water - completely soluble

because it is polar. As alcohol molecule gets bigger the polar

part becomes less significant so the alcohol becomes less soluble in water and more soluble in cyclohexane

Butan-1-ol is – (i) soluble in cyclohexane – (ii) not very soluble in water

The polar OH group is becoming less significant as the molecule gets bigger

Comparison with water

Both have polar OH groups Alcohols have a non-polar part Both form hydrogen bonds between their

molecules Water is more polar and has a greater

capacity to form hydrogen bonds and so has a higher boiling point than methanol or ethanol

Methanol

Methanol: is toxic (can cause blindness, insanity and death)

It is added to industrial alcohol to prevent people drinking it. This mixture is called methylated spirits.

The methanol acts as a denaturing agent – it renders a substance unfit for purpose without destroying the usefulness or applications of the substance. A purple dye is often added as a warning.

Ethanol Ethanol: is produced by fermentation. Fruits provide

the sugar and yeast may need to be added.

The enzyme zymase in yeast catalyses the reaction.

C6H12O6 2C2H5OH + 2CO2

Alcoholic Drinks

Ingredient

Drink % (v/v) alcohol

Grapes Wine 12

Apples Cider 4.5

Malted grain

Beer 5

Ethanol

To produce drinks of higher alcohol concentration the fermented liquids must be distilled.

Spirits (whiskey, brandy, gin, vodka) contain 40% alcohol.

Gasohol

Ethanol obtained from sugar cane is used for making gasohol in Brazil. This is then used as a fuel.

Uses of ethanol

1. Alcoholic drinks

2. Fuel

3. Solvent (can dissolve both polar and non-

polar solutes)