ALKANES

Alkanes are saturated, open chain hydrocarbons containing carbon-carbon single bonds. e.g., methane (CH₄), ethane (C₄H₆) propane (C₃H₈), etc.These hydrocarbons are inert under normal conditions [i.e.,do not react with acids. bases and other reagents). Hence, they were earlier known as paraffins (Latin : parum-little; affins-affinity) Alkanes exhibit chain isomensm, position isomerism and conformational isomerism. Some example of alkanes are Methane , Ethane , Propane , etc.

        MODES OF PREPARATION OF ALKANES

1) FROM HYDROGENATION OF UNSATURATED HYDROCARBONS

When hydrogen is passed to unsaturated hydrocarbons(alkenes or alkynes) in the presence of Nickel , Platinum or Palladium as catalyst at about 250-300 degree C alkane is formed

2) SODALIME DECARBOXYLATION

When sodium salt of carboxylic acid is heated at about 360 degree C with sodalime alkene is formed

3) BY WURTZ REACTION

When an alkyl halide is treated with metallic sodium in presence of dry diethyl ether alkane containing double the number of carbon atoms than that in alkyl halide is formed

4) BY REDUCTION OF ALKYL HALIDE

When haloalkanes is treated with atomic hydrogen in presence of alcoholic Zinc and Copper alkane is formed

5) BY KOLBE'S ELECTROLYSIS

When a concentrated aqueous solution of the sodium or potassium salt of monocarboxylic acid is electrolyzed , alkane is produced at anode with liberation of carbondioxide