Stereochemistry as Mechanistic Evidence · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading reactions from their stereochemistry

Science · Chemistry · ages 19-20
Name ______________________   Date ____________

  1. How do stereospecific and stereoselective differ?

    • They mean exactly the same thing
    • Stereospecific ties each start to its own product, stereoselective merely prefers one
    • Stereoselective is stricter than stereospecific

  2. In the ideal model, a planar intermediate is achiral with both faces equally open. What does the model predict for the product stereochemistry?

    • It gives a racemic mix
    • It always gives a single enantiomer
    • It keeps the starting shape with no change at all

  3. Clean inversion at a stereocentre argues for a backside attack.

    Circle one:   True   False

  4. One geometric isomer of starting material gives one product, the other isomer gives a different product. What is the reaction?

    • Stereoselective but not stereospecific
    • Unrelated to stereochemistry
    • Stereospecific

  5. A single enantiomer substrate gives a fully racemic product. What intermediate fits?

    • A flat intermediate
    • A concerted backside attack
    • No intermediate at all

  6. A reaction of one enantiomer gives product with clean inversion and no scrambling. In the ideal model, what do you rule out?

    • A concerted backside attack
    • A free planar intermediate with both faces open
    • Any reaction at the stereocentre in any solvent

  7. A student claims speed data alone prove a backside attack. Why is that weak?

    • Speed data can never support any mechanism
    • Stereochemistry testifies directly while speed only hints
    • A fast reaction must be a backside attack

  8. A student sees weak opposite rotation and declares competing pathways proven. What is missing?

    • Nothing is missing; rotation alone proves it
    • A faster reaction time would prove it
    • A pure inverted reference with full conditions, plus other evidence; one shielded route fits too
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Answer key

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

Reading reactions from their stereochemistry W1-mt_YtagP8C0Wi-s1

  1. Stereospecific ties each start to its own product, stereoselective merely prefers one · Mapping is strict, preference is loose.
  2. It gives a racemic mix · In the ideal model both faces lie equally open, so both mirror products form equally.
  3. True · The umbrella flip is the fingerprint of that route.
  4. Stereospecific · Each start maps to its own product.
  5. A flat intermediate · A free planar shape with both faces open scrambles fully.
  6. A free planar intermediate with both faces open · A free flat shape with both faces open would have leaked the mirror product.
  7. Stereochemistry testifies directly while speed only hints · Geometry reads from the products; speed alone cannot name the route.
  8. A pure inverted reference with full conditions, plus other evidence; one shielded route fits too · Rotation alone fits a shielded single route too. The claim needs a pure reference with conditions plus other evidence.
Worksheet · LightMySky