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 maps each start to one product, stereoselective merely prefers one
    • Stereoselective is stricter than stereospecific

  2. What does a planar intermediate do to the stereochemistry of the product?

    • It forces attack from both faces, giving a racemic mix
    • It always gives a single enantiomer
    • It destroys all atoms in the molecule

  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 open to both faces
    • A concerted backside attack
    • No intermediate at all

  6. A reaction of one enantiomer gives product with clean inversion and no scrambling. What do you rule out?

    • A concerted backside attack
    • A planar intermediate
    • Any reaction at the stereocentre

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

    • Speed data are always fabricated
    • Stereochemistry testifies directly while speed only hints
    • Backside attacks have no speed at all

  8. A single enantiomer gives almost racemic product with net inversion. What happened?

    • One pure backside attack with no side route
    • The starting material was racemic
    • Competing pathways: mostly backside attack plus a planar leak
LightMySky · lightmysky.comW1-mt_YtagP8C0Wi-s1

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 maps each start to one product, stereoselective merely prefers one · Mapping is strict, preference is loose.
  2. It forces attack from both faces, giving a racemic mix · Both faces lie 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 open to both faces · Only a planar shape scrambles fully.
  6. A planar intermediate · A flat shape would have leaked the mirror product.
  7. Stereochemistry testifies directly while speed only hints · Read the geometry from the products first.
  8. Competing pathways: mostly backside attack plus a planar leak · Scrambling plus a lean means two routes ran together.
Worksheet · LightMySky