Alcohols • Methanol CH3OH • Ethanol C2H5OH • Propan-1-ol C3H7OH • Propan-2-ol C3H7OH • Butan-1-ol C4H9OH • Butan-2-ol C4H9OH
Classification of alcohols • 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. C6H12O62C2H5OH + 2CO2
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 • Alcoholic drinks • Fuel • Solvent (can dissolve both polar and non-polar solutes)