Preparation

From Alkyl Halides (By Wurtz Reaction)

Alkyl halides are halogen derivatives of alkanes with general formula R-X. They can be used to prepare alkanes by Wurtz reaction:

It involves the chemical reaction between alkyl halides (usually bromides and iodides) and metallic sodium in the presence of dry ether. The product is the symmetrical alkane containing twice the number of carbon atoms present in the alkyl halide.

For examples

From Unsaturated Hydrocarbons

Unsaturated hydrocarbon can be converted into alkanes by catalytic hydrogenation. The catalyst used may be nickel, platinum or palladium. These metals absorb dihydrogen gas on their surface and weaken the hydrogen-hydrogen bond. Platinum and palladium catalyst the reaction at room temperature while nickel requires higher temperature and pressure. The reaction is called Sebatier and Senderen’s reaction.

The process of addition of hydrogen to an unsaturated compound in presence of a catalyst is called hydrogeneration or reduction.