Example of reduction of alkyl halide except flouride.

There are many reactions involves in this.
The oxidation state of C in alkyl halide is +1 due to halogen as halogen is more reactive to C. Two types of reactions are involved in reduction of alkyl halide.
  • Formation of alkane from alkyl halide
  • Formation of any of the organometallic reagent like grignard reagent or organolithium etc.

In foramation of alkane or grignard reagent Carbon is reduced by gaining electrons and acquire the negative oxidation state.

Grignard’s reagent : Allkyl halides are reacted with Magnesium in presence of dry ether to form alkylmagnesium halides. This then reacts readily with water to give alkane. Here the alkyl halide used are mainly bromide and chloride.

R-X + Mg → (in dry ether) R-Mg-X

  R-Mg-X + H2O → R-H + Mg(OH)X
For example :
 H2O + CH3MgCl→ CH4 + MgCl(OH)
 

  • Wurtz reaction : An alkyl halide is treated with metallic sodium in presence of dry diethyl ether and an alkane with double the number of carbon atoms in the alkyl halide is formed. Here any kind of alkyl halide can be used. It can be bromide , chloride or iodide.

R-X + 2Na + X-R → (dry ether) R-R + 2NaX
‚Äč
CH3Cl+2Na+CH3Cl Dry ether CH3-CH3+2NaCl

 

  • Reduction of alkyl halides using nascent H to form alkane Reduction of alkyl halides (preferably bromides or iodides) in presence of nascent hydrogen yields alkanes. Nascent hydrogen is prepared by:

Zn + 2HCl→(in presence of alcohol) ZnCl2 + 2[H] (nascent hydrogen)

R-X + 2[H] → R-H + HX

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