Haloalkanes and Haloarenes

Introduction, Methods of Preparation

  • Preparation of Haloalkanes:
    (a) Halogen exchange:
    (i) 2 RCl (or Br) + Hg2F2 (AsF3 (or) SbF3 (or) AgF) → 2RF + H2Cl2
                                                                                     {Swart reaction}
    (ii) \tt RCl+NaI(or \ KI)\xrightarrow[(or)Methanol]{{Acetone}}RI+NaCl
                                                                                     {Finkelstein reaction}
  • (vii) Use of SOCl2 is the best method to convert 1° alcohols to alkyl chlorides. SO2 and HCl being gases, leave the mixture.
    (viii) 3° and 2° alcohols and hindered alcohols of 1° follows SN1 mechanism.
    (ix) 1° alcohols follow SN2 mechanism through 100% walden inversion.
    (d) From silver salt of acid:
    (i) RCOOAg + Cl2((or) Br2) → RCl + CO2 + AgX (Borodine-Hunsdiecker reaction)
    (ii) 2RCOOAg + I2 → RCOOR + CO2 + 2AgI (Birnbaum Simonini reaction)
    (e) From acid: 2RCOOH + 2Br2 + HgO → HgBr2 + 2R-Br + 2CO2 + 2H2O (Cristol reaction)
  • Preparation of Haloarenes:
  • (c) Phenol can be converted into chlorobenzene by the reaction with PCl5 but the method is not good because more than 75% Phenol is wasted in the formation of triphenyl phosphate.
                 C6H5OH + PCl5 → C6H5Cl + POCl3
                 3C6H5OH + POCl3 → (C6H5)3 PO4 + 3 HCl

Part1: View the Topic in this Video from 0:50 to 57:05

Part2: View the Topic in this Video from 0:40 to 30:30

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