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Equivalent Ligands

[ "article:topic", "authorname:ggunawardena" ]
  • Page ID
    39301
  • Equivalent ligands or, more completely, chemically equivalent ligands in an organic molecule are like ligands that have identical chemical properties under all or a specified set of conditions.  A test known as the replacement test is used to find if two like ligands in a molecule are equivalent.

    eg:

     

     

    Apply the replacement test to find if the two hydrogen atoms in 1 are equivalent:

    Step 1:
    Label the two hydrogen atoms in 1 for identification purposes.

     

     

    Step 2:
    Replace H (a) in 1 with a hypothetical atom (X).

     

     

    Step 3:
    Replace H (b) in  1 with the same hypothetical atom, X.

     

     

    Step 4:
    Compare molecules 2 and 3. They are superimposable on each other, meaning that they are identical.  Identical molecules have identical chemical properties under all conditions.  Since the replacement of H (a) and of H (b) in 1 with the same atom leads to molecules that have identical chemical properties under all conditions, H (a) and H (b) have identical chemical properties under all conditions, i.e., H (a) and H (b) are equivalent under all conditions.

    see also homotopic, enantiotopic, diastereotopic, constitutionally heterotopic