What are alkanes?
Alkanes are compounds formed exclusively by carbon and hydrogen (hydrocarbons) that contain only single carbon-carbon bonds.
Types of alkanes
Alkanes are classified as linear, branched, cyclic, and polycyclic.
Nomenclature of alkanes
Alkanes are named with an -ane suffix on the prefix that indicates the number of carbons in the molecule (methane, ethane, propane...).
Physical properties of alkanes
The melting and boiling points of alkanes are low and increase as the number of carbons increases due to interactions between molecules by London forces. Linear alkanes have higher boiling points than their branched isomers.
Conformational isomers
Alkanes are not rigid due to rotation around the C-C bond. The multiple shapes created by these rotations are called conformations.
Newman Projection
The energy of the different conformations can be seen in Newman projections. For example, in ethane, the eclipsed conformation has the highest energy due to repulsions between hydrogens.
Potential energy diagrams
The different conformations of the alkanes can be represented in a potential energy diagram where we can see which conformation is more stable (minimum energy) and the energy required to move from one conformation to another.
Combustion of alkanes
Due to their low reactivity, alkanes are also called paraffins. The most important reactions of this group of compounds are radical halogenations and combustion. Combustion is the combination of the hydrocarbon with oxygen to form carbon dioxide and water.
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