Ethanol molecule

Educational value

• Ethanol, the common alcohol found in beer, wine and spirits, is a colourless, flammable liquid with a distinctive odour. It is produced naturally by the fermentation of sugars with yeast. To cater for its common uses as a fuel and a versatile solvent, ethanol is sold in a ‘denatured’ form to prevent it being drunk. Denatured ethanol, usually called ‘methylated spirits’ contains some additives that are poisonous (for example methanol) and others with unpleasant tastes.
• The atoms in the molecule are connected by single covalent bonds. A covalent bond is formed when atoms share electrons and a single covalent bond has two shared electrons, one contributed by each atom. Because carbon atoms are able to contribute four electrons, they are able to participate in four single bonds, whereas the hydrogen atoms can each form only one bond. The oxygen atom can contribute two electrons, and so can participate in two single bonds.
• The chemical properties of ethanol are largely determined by the -OH group. A reactive group such as this is called a functional group, and this particular group is called the hydroxyl functional group. Molecules that carry the same functional group have similar chemical properties and consequently form a family. Ethanol and all other substances carrying the hydroxyl functional group are known as alcohols.
• Because oxygen atoms attract electrons more strongly than hydrogen atoms, the bond between them is polar. As a result, the hydroxyl groups on adjacent ethanol molecules attract each other strongly, with the hydrogen atom forming a bridge between oxygen atoms on separate molecules. This type of attraction is known as hydrogen bonding, and it is responsible for the fact that ethanol is a liquid at room temperature, whereas ethane, which also has molecules containing two carbon atoms, is a gas.
• This is not the only possible way of connecting this set of atoms. The oxygen atom could be connected between the two carbon atoms, forming a molecule of a different substance, dimethyl ether. Substances that have the same chemical formula but different molecular structures, such as dimethyl ether and ethanol, are called structural isomers.
• The type of model shown here, called a ball-and-stick model, is one of several ways of modelling molecules. This type is useful because it clearly shows the geometry of the molecule and the order (single, double or triple) of the bonds. However, because 'sticks' are used to represent bonds, this type of model does not represent the actual shape of the molecule as well as 'space-filling' models do.

Year level

6; 7; 8; 9; 10; 11; 12

Topics Ethanol Molecules Bonding (Chemistry) Dipoles Curves Central tendency