5.1 Alcohols, carboxylic acids and esters
Series of molecules that have a general formula are called homologous series.
The alkanes and the alkenes are two homologous series made of only hydrogen and carbon atoms.
The homologous series of alcohols contain the -OH functional group.
The homologous series of carboxylic acids contain the -COOH functional group.
The homologous series of esthers contain the -COO- functional group
5.2 Properties and uses of alcohols
Alcohols are used as solvents and fuels, and ethanol is the main alcohol in alcoholic drinks.
Alcohols withs smaller molecules i.e. methanol and ethanol, mix well with water and produce neutral solutions.
Alcohols burn in air, forming carbon dioxide and water.
With sodium metal, alcohols react to form a solution, and hydrogen gas is given off.
Ethanol can be oxidised to ethanoic acid, either by chemical oxidising agents or by the action of microbes.
5.3 Carboxylic acids and esters
Solutions of carboxylic acids have a pH value less than 7. Carbonates gently fizz in their acidic solutions, releasing carbon dioxide gas.
Aqueous solutions of weak acids have a higher pH value than solutions of strong acids with the same concentration.
Acids that ionise completely in aqueous solutions are known as strong acids.
Acids that do not ionise completely in aqueous solutions are known as weak acids.
Esters are made by reacting a carboxylic acid and an alcohol together with an acid catalyst.
Esters are volatile compounds used in flavourings and perfumes.
5.4 Organic issues
Alcohols, carboxylic acids and esters have many uses which benefit society.
Some of these subtsances, such as ethanol and solvents, can be abused.
In future, the use of biofuels such as ethanol and esters, could help society as crude oil supplies run out.
Future uses of biofuels might confict with the need to feed the world.