Aldol and Claisen: Building Carbon Skeletons · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Joining carbons with carbonyls

Science · Chemistry · ages 20-21
Name ______________________   Date ____________

  1. How does an aldol condensation differ from an aldol addition?

    • It adds a second enolate to the product
    • It runs without any carbonyl partner
    • It follows addition with dehydration to an enone

  2. What is the product of an aldol addition?

    • A beta-hydroxy carbonyl compound
    • A beta-keto ester
    • A conjugated diene with no oxygen

  3. Ketones stop at the addition product under the addition conditions because they have no group able to leave.

    Circle one:   True   False

  4. Why can mixing two different carbonyl partners give four products?

    • Because each partner can play either role
    • Because aldol products always split in two
    • Because heating doubles every molecule

  5. An ester enolate attacks another ester. What forms?

    • A beta-hydroxy carbonyl that cannot change further
    • A beta-keto ester after alkoxide leaves
    • Two unchanged esters plus water

  6. Which partner makes a clean acceptor for a crossed aldol?

    • An aldehyde with no alpha hydrogens
    • A ketone with two different alpha positions
    • An ester enolate in large excess

  7. A crossed aldol of two enolisable aldehydes gives a mess. What had to be controlled?

    • The temperature of the room
    • Which partner enolises and which accepts
    • The colour of the reaction flask

  8. An enone is cut at its alpha-beta bond for retrosynthesis. Where did each side come from?

    • The carbonyl side was the acceptor and the beta side the donor
    • The carbonyl side was the donor and the beta side the acceptor
    • Both sides came from a single Claisen donor
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Answer key

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

Joining carbons with carbonyls W1-mt_LYpEw4EpOX-s1

  1. It follows addition with dehydration to an enone · Heat removes water and the conjugated enone appears.
  2. A beta-hydroxy carbonyl compound · Enolate plus carbonyl places OH one carbon from the new carbonyl.
  3. True · With nothing to eject, substitution cannot follow.
  4. Because each partner can play either role · Either partner can donate or accept, giving four pairings.
  5. A beta-keto ester after alkoxide leaves · Alkoxide departure turns addition into substitution.
  6. An aldehyde with no alpha hydrogens · No alpha hydrogens means it cannot donate, only accept.
  7. Which partner enolises and which accepts · Unplanned roles multiply into four products.
  8. The carbonyl side was the donor and the beta side the acceptor · The donor keeps its carbonyl; the acceptor carbonyl becomes the beta carbon.
Worksheet · LightMySky