Alkanes

What are alkanes?

Alkanes are aliphatic hydrocarbons in the form of linear or branched chains with the general formula CnHn.

alkane functional group

Nomenclature of alkanes

Follow the link for a summary of the formulation and nomenclature rules for alkanes, branched alkanes and cycloalkanes.

Reactions of alkanes

Compared to other functional groups, they are not very versatile in organic synthesis and the reactivity of these functional groups is mainly limited to halogenation and combustion reactions which are detailed in the section on alkane reactions.

Analysis of alkanes

Due to their lack of reactivity, there are few specific reactions to identify saturated hydrocarbons by chemical reactions. It is generally necessary to check their indirect identification by exclusion.

In order to characterize them, different physicochemical properties such as boiling point, density or refractive index are generally determined.

The saturated hydrocarbons stand out for the following main characteristics:

  • Exceptionally simple IR spectrum. The most intense bands appear near 2900, 1460 and 1370 cm-1 (with the absence of the last peak if no methyls are present).
  • Negative assay on the formation of the charge transfer complex with iodine. A small iodine crystal in a few drops of liquid will give violet solution.
  • Insolubility in cold concentrated H2SO4.