Retrosynthesis: Disconnections and Synthons · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Planning backwards from the target

Science · Chemistry · ages 21-22
Name ______________________   Date ____________

  1. What is a synthon?

    • The solvent used to clean glassware
    • An idealized fragment with needed polarity
    • A cheap starting material from the catalogue

  2. What makes a disconnection valid?

    • It matches a forward reaction you can run
    • It breaks as many bonds as possible at once
    • It avoids naming any forward reaction

  3. An alcohol sits next to a former carbonyl in your target. Which disconnection does this suggest?

    • An aldol disconnection
    • An amide coupling
    • Grignard cut

  4. Your target holds a beta-hydroxy carbonyl pattern. Which transform do you use?

    • Esterification of an acid and an alcohol
    • Aldol from an enolate plus a carbonyl
    • Amide formation from an acid and an amine

  5. You need a carbanion synthon to attack a carbonyl acceptor. Which real reagent do you pick?

    • Grignard donor
    • An acid plus an alcohol
    • An overalkylated amine

  6. A shorter route from cheap available materials beats a clever long one.

    Circle one:   True   False

  7. A disconnection with no known forward reaction counts as valid.

    Circle one:   True   False

  8. Your target holds an alpha beta unsaturated carbonyl. Which disconnection do you mark?

    • Grignard on an ester
    • Amide to acid plus amine
    • Retro aldol cut
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Answer key

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

Planning backwards from the target W1-mt_0EJbkDPo2P-s1

  1. An idealized fragment with needed polarity · It names the polarity you need before you pick a real reagent.
  2. It matches a forward reaction you can run · Every cut must rejoin through a known reliable reaction.
  3. Grignard cut · Alcohol next to a former carbonyl maps to a Grignard cut.
  4. Aldol from an enolate plus a carbonyl · A beta-hydroxy carbonyl maps to an aldol cut.
  5. Grignard donor · Grignard carbon is a donor that matches the carbonyl acceptor.
  6. True · Fewer steps and cheap feedstocks mean higher yield and lower burden.
  7. False · A cut is valid only when a real reaction can rejoin it.
  8. Retro aldol cut · The enone pattern points straight at the retro aldol transform.
Worksheet · LightMySky