Organic Chemistry - Alkanes

Alkanes are saturated hydrocarbons, meaning they contain only single covalent bonds between carbon atoms ($C-C$) and carbon and hydrogen atoms ($C-H$).

They belong to a homologous series with the general formula $C_nH_{2n+2}$, where $n$ is the number of carbon atoms.

Alkanes are generally unreactive due to the high bond enthalpy of $C-C$ and $C-H$ bonds, but they undergo combustion and substitution reactions.

Physical properties: Boiling and melting points increase as the molecular mass increases because the strength of London dispersion forces (Van der Waals forces) increases with the number of electrons.

Structural isomerism: Alkanes starting from butane ($C_4H_{10}$) can exist as structural isomers, having the same molecular formula but different branching in their carbon chains.

Fractional Distillation: Alkanes are obtained from crude oil using fractional distillation, which separates mixtures based on differences in boiling points.

Substitution Reaction: Alkanes react with halogens (e.g., $Cl_2$, $Br_2$) in the presence of Ultraviolet ($UV$) light via a free-radical mechanism (Initiation, Propagation, and Termination).

Cracking: Large alkane molecules are broken down into smaller, more useful alkanes and alkenes using high temperatures and catalysts ($Al_2O_3$ or $SiO_2$).