free radical substitution

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Created by
alara kaya

Cards (19)

  • What is homolytic fission?
    The breaking of a covalent bond where each atom retains one electron.
    Homolytic fission is described in the specification in terms of each bonding atom receiving one electron from the bonded pair forming two radicals
    One electron from the bond pair goes to each atom, forming a free radical.
  • What is the mechanism for the reaction of compounds with halogens in the presence of ultraviolet radiation to form organic compounds?
    Free radical subsitution
  • How are halogenoalkanes formed from alkanes?

    radical substitution
  • In the presence of what does alkane react with halogens?
    UV radiation/light
  • What are the 3 stages of free radical substitution?
    Initiation
    Propagation
    Termination
  • What is initiation?
    breaking the halogen bond to form 2 free radicals
    e.g Br2 ->2Br.
  • What is propagation?
    chain part of the reaction where products are formed, but free radical remains
    there are 2 stages
  • What is termination?
    free radicals are removed and stable products are formed
  • What are the equations for the reaction of CH4 with Cl2 to form CH3Cl?
    initiation: Cl2 -> 2Cl. (in presence of UV light)
    propagation: 1) CH4 + Cl. -> .CH3 + HCl
    2) .CH3 + Cl2 -> CH3Cl + Cl.
    termination: .CH3 + Cl. -> CH3Cl
    2Cl. -> Cl2
    .CH3 + .CH3 -> CH3CH3
  • What is a free radical?
    a reactive species which possess an unpaired electron
  • What is the equation for the overall decomposition of ozone into oxygen?
    2O3 -> 3O2
  • What occurs in the termination step of Free Radical Substitution?
    two radicals join to end the chain reaction and form a stable product
  • What occurs in the initiation step of Free Radical Substitution?
    In the presence of UV radiation, the diatomic halogen is broken down into 2 free radicals
    This is an example of homolytic fission - each atom gets one electron from the covalent bond
  • How are halogenoalkanes classified?
    according to how many carbon atoms are attached to the C-H group
    primary = 1
    secondary = 2
    tertiary = 3
  • How would you describe the propagation step of Free Radical Substitution?
    A hydrogen is replaced and the Cl free radical is reformed as a catalyst
  • Whys is the C-F bond not affected by UV?
    it is stronger than the C-Cl bond
  • What are 2 limitations of using radical substitution in organic synthesis?
    further substitutions occur
    more than one termination step/ radicals react with each other to form other products
    substitution at different positions along chain
  • Why is the initiation step an example of homolytic fission?
    the breaking of a Br- Br / Cl-Cl bond
    one electron from the electron pair goes to each atom
  • what is homolytic fission?
    one electron from the bond (pair) goes to each atom