Alkanes [Paraffines]

         "Alkanes are saturated hydrocarbon containing only carbon-carbon single bond in their molecules."

         Alkanes are less reactive so known as paraffins; because under normal conditions alkanes do not react with acids, bases, oxidising agents and reducing agent.

         General formula : C_nH_2n+2

         Examples are CH₄, C₂H₆, C₃H₈,

General Methods of preparation

         (i) By catalytic hydrogenation of alkynes and alkenes (Sabatie and sanderen's reaction)

•          Methane is not created by this process

         (ii) Birch reduction :

         (iii) From alkyl halide

         (a) By reduction : 

         (b) With hydrogen in existence of pt/pd : 

          (c) With HI in existence of Red phosphorus :    

         (iv) By Zn-Cu couple :

         (v) Wurtz reaction :

•          R-Br or RI preferred in this reaction. The total result in that reaction is the formation of even no. of carbon atoms in molecules.

         (vi)   Frankland's reaction :

         (vii) Corey-house synthesis   

•          Reaction is suitable for odd number of Alkanes.

         (viii) From Grignard reagent

         (a) By action of acidic 'H' :

         (b) By reaction with alkyl halide :

      (ix) From carboxylic acids

         (a) Laboratory method [Decarboxylation reaction or Duma reaction]                                                  

•          NaOH and CaO is in the ratio of 3 : 1. (Sodalime)

         (b) Kolbe's synthesis :

         At anode [Oxidation] :

         At cathode [Reduction] :

•         Both free radical and ionic process are required in this reaction.

         (c) Reduction of carboxylic acid :

         (x) By reduction of alcohols,  ketones, acid derivatives or aldehyde

         q Aldehyde and ketones when reduced with conc. HCl and amalgamated zinc also yield alkanes.

         Clemmenson reduction :

•          Ketones and aldehydes (>C = O) may be converted to hydrocarbon in presence of excess of hydrazine and sodium alkoxide on heating.

         Wolff-kishner reduction :

         (xi) Hydroboration of alkenes

         (a) On treatment with acetic acid

         (b) Coupling of alkyl boranes by incomes of silver nitrate

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