Alkanes: Physical Properties
At roomtemperature, alkanes from to are gases, from to they are liquids and higher alkanes are solids and waxlike to some extent . In saturated alkanes, only van der Waals forces are important as attractive forces. In general, alkanes show a relatively low reactivity. However, protonation, oxygenation, pyrolysis, radiolysis, and photolysis are possible under extreme reaction conditions. Oxidation of alkanes can also be carried out electrochemically. Lower alkanes in particular are highly flammable and form explosive mixtures (methane, benzene) with air (oxygen). Solubility of alkanes in water is very low.
The physical properties of alkanes follow a similar trend as seen in the regularity of alkane structures. Thus, the larger the number of carbon atoms the higher the boiling points. However, the melting point curve does not exhibit the same smooth gradation. Small, non-linear increases in melting point temperatures can be observed between odd- and even-numbered alkanes.