Elementary Steps of Catalysis: Oxidative Addition and Insertion · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The small steps behind big catalytic cycles

Science · Chemistry · ages 20-22
Name ______________________   Date ____________

  1. What happens to the oxidation state and electron count in oxidative addition?

    • Both stay exactly the same
    • Both fall by 2
    • Both rise by 2

  2. A metal breaks H2 apart and takes both hydrogen fragments onto itself. Which step is this?

    • Oxidative addition
    • Migratory insertion
    • Beta hydride elimination

  3. In migratory insertion the metal oxidation state stays unchanged while the electron count drops by two.

    Circle one:   True   False

  4. A sixteen electron complex meets an aryl halide and undergoes oxidative addition. What is the product count and state?

    • Fourteen electrons at a lower oxidation state
    • Eighteen electrons at an oxidation state higher by 2
    • Sixteen electrons at the same oxidation state

  5. How do you tell migratory insertion apart from simple addition?

    • Insertion changes the oxidation state and addition never does
    • Identify which ligand moved, since simple addition has no mover
    • Insertion always needs light while addition always needs heat

  6. What must be true of a metal centre before oxidative addition can occur?

    • It must already sit at its highest possible oxidation state
    • It must have room for two fragments and a low enough oxidation state to climb by two
    • It must carry no ligands at all

  7. After a migratory insertion the cycle stalls with no open site. What went wrong in the analysis?

    • Insertion always destroys the complex, so stalling is normal
    • Nothing went wrong, since insertion never opens a site
    • The bookkeeping slipped, since insertion drops the count by two and must open a vacant site

  8. A student labels a step where a hydrogen shifts from the chain to the metal as reductive elimination. What is wrong?

    • Nothing is wrong, since every hydrogen shift is reductive elimination
    • Hydrogen shifts to the metal never happen in any cycle
    • That shift is beta hydride elimination, while reductive elimination ejects two fragments and drops the oxidation state by two
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Answer key

For grown-ups. Fold this page away before handing over the rest.

The small steps behind big catalytic cycles W1-mt_VVLGGh8QZ_-s1

  1. Both rise by 2 · Two new fragments each bring one oxidation unit and one electron pair share, lifting both tallies.
  2. Oxidative addition · Breaking one bond and binding both fragments to the metal is the oxidative addition pattern.
  3. True · Only the ligands reorganise, so the metal oxidation level never moves.
  4. Eighteen electrons at an oxidation state higher by 2 · Plus two electrons on sixteen gives eighteen, with the oxidation state lifted by two.
  5. Identify which ligand moved, since simple addition has no mover · The migrating ligand is the fingerprint that simple addition lacks.
  6. It must have room for two fragments and a low enough oxidation state to climb by two · An unsaturated centre such as a sixteen electron complex can accept the pair and the climb.
  7. The bookkeeping slipped, since insertion drops the count by two and must open a vacant site · The fixed minus two change is exactly the opening the next ligand needs.
  8. That shift is beta hydride elimination, while reductive elimination ejects two fragments and drops the oxidation state by two · Direction and bookkeeping differ: one moves hydrogen inward, the other couples fragments outward.
Worksheet · LightMySky