Substitution Against Elimination: Predicting the Major Product · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Picking the winner of four routes

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

  1. How do nucleophile strength and base strength differ?

    • They are two names for the same property
    • Nucleophile strength attacks carbon, base strength grabs protons
    • Base strength attacks carbon, nucleophile strength grabs protons

  2. What is the first step when predicting substitution versus elimination?

    • Check the temperature first
    • Guess from the shape of the flask
    • Check the substrate class first

  3. Methyl and primary substrates forbid SN1 and E1.

    Circle one:   True   False

  4. Why does a bulky base give the less substituted alkene?

    • It takes the least hindered proton, which it alone can reach
    • It prefers crowded protons
    • Bulk always causes substitution instead

  5. A tertiary halide meets a hindered alkoxide in warm alcohol. What dominates?

    • SN2 substitution at carbon
    • Elimination to the less substituted alkene
    • No reaction at all

  6. What does raising the temperature favour, and why?

    • Substitution, because heat loves single products
    • Nothing, temperature never matters
    • Elimination, because splitting gains disorder that heat amplifies

  7. Doubling the reagent concentration leaves the product ratio unchanged. What does that tell you?

    • The competing routes are both bimolecular
    • A unimolecular route dominates, since it ignores concentration
    • Concentration was measured wrongly

  8. A student treats iodide as a strong base because it is a great nucleophile. What is the error?

    • Iodide is neither nucleophilic nor basic
    • Strength at carbon does not imply strength at protons, and iodide is a weak base
    • Bases never act as nucleophiles
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Answer key

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

Picking the winner of four routes W1-mt_6WyFC9kQuu-s1

  1. Nucleophile strength attacks carbon, base strength grabs protons · Iodide shows the split: great nucleophile, weak base.
  2. Check the substrate class first · Substrate class forbids routes before anything else matters.
  3. True · They cannot ionize, so only bimolecular routes stay open.
  4. It takes the least hindered proton, which it alone can reach · Reach decides. The open proton is the only one available.
  5. Elimination to the less substituted alkene · Tertiary forbids SN2, bulk blocks carbon, heat backs splitting.
  6. Elimination, because splitting gains disorder that heat amplifies · More particles from fewer means entropy cheers for heat.
  7. A unimolecular route dominates, since it ignores concentration · Only bimolecular rates answer to concentration.
  8. Strength at carbon does not imply strength at protons, and iodide is a weak base · Each strength belongs in its own place in the tree.
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