Hydroboration, Oxidation and Cleavage of Alkenes and Alkynes · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Putting oxygen exactly where you want it

Science · Chemistry · ages 19-21
Name ______________________   Date ____________

  1. Why is hydroboration-oxidation a syn addition?

    • The molecule spins halfway through the reaction
    • Boron and hydrogen add to the same face and oxidation keeps that geometry
    • The OH is smaller than boron so it slips past

  2. You treat propene with borane, then peroxide and base. Which alcohol forms?

    • 1-propanol
    • 2-propanol
    • Propanone

  3. Cold dilute oxidation of an alkene stops at the syn diol.

    Circle one:   True   False

  4. You hydrate propyne with aqueous acid. Which carbonyl compound forms?

    • Propanone
    • Propanal
    • Propanoic acid

  5. Ozonolysis of an unknown alkene gives ethanal and propanone. What was the alkene?

    • But-2-ene
    • 2-methylpropene
    • 2-methyl-2-butene

  6. You want 2-propanol from propene. Which route do you choose?

    • Ozonolysis
    • Borane then peroxide
    • Acid hydration

  7. A student predicts propanal from propyne plus aqueous acid. That prediction is correct.

    Circle one:   True   False

  8. You want hexanedioic acid from cyclohexene. Which conditions do you use?

    • Hot concentrated oxidant
    • Cold dilute oxidant
    • Borane then peroxide and base
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Answer key

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

Putting oxygen exactly where you want it W1-mt_Ny7vC57rqc-s1

  1. Boron and hydrogen add to the same face and oxidation keeps that geometry · One-face addition plus retention at oxidation puts H and OH on the same face.
  2. 1-propanol · Hydroboration-oxidation puts the OH on the less substituted end carbon.
  3. True · Mild conditions add one OH per carbon and go no further.
  4. Propanone · Acid hydration follows Markovnikov, so the terminal alkyne gives the ketone.
  5. 2-methyl-2-butene · Rejoining ethanal and propanone at their carbonyl carbons gives 2-methyl-2-butene.
  6. Acid hydration · 2-propanol has OH on the more substituted carbon, which is the Markovnikov product.
  7. False · Acid hydration of a terminal alkyne gives the ketone propanone, not the aldehyde.
  8. Hot concentrated oxidant · Only harsh oxidation cuts the ring open all the way to the diacid.
Worksheet · LightMySky