Molecular Recognition: Preorganisation, Complementarity and Binding Constants · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Why some hosts grip a hundred times tighter

Science · Chemistry · ages 23-24
Name ______________________   Date ____________

  1. Two hosts differ a hundredfold in K at room temperature. What energy gap is that?

    • About 1 kilojoule per mole
    • About 11 kilojoules per mole
    • About 110 kilojoules per mole

  2. What does a larger binding constant K tell you?

    • The bound complex dominates at equilibrium
    • The binding releases no heat
    • The host dissolves better

  3. A macrocyclic host binds tighter than its open-chain analogue because it is preorganised.

    Circle one:   True   False

  4. How would you raise selectivity between two similar guests?

    • Reshape the pocket so the rival strains while the wanted guest fits
    • Dilute both guests
    • Strengthen all contacts equally

  5. Binding is enthalpy driven but weak overall. What is the most likely culprit?

    • Too much product
    • Poor contacts
    • An entropy penalty from a floppy host

  6. Which titration method suits a very strong binder?

    • NMR shifts at high concentration
    • Sensitive optical signals at low concentration
    • Melting point reading

  7. Fitting only the titration endpoint determines K as reliably as fitting the whole curve.

    Circle one:   True   False

  8. Calorimetry shows great heat yet K stays modest. What do you change?

    • Switch to a weaker guest
    • Add more contact groups
    • Preorganise the host to cut the entropy penalty
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Answer key

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

Why some hosts grip a hundred times tighter W1-mt_Ub84WUj1Gg-s1

  1. About 11 kilojoules per mole · The log relation turns a factor of 100 into roughly 11 kilojoules per mole.
  2. The bound complex dominates at equilibrium · K compares bound against unbound, so bigger means more complex.
  3. True · The ring already holds the bound shape, so binding pays less entropy.
  4. Reshape the pocket so the rival strains while the wanted guest fits · Selectivity comes from fit differences, not raw grip.
  5. An entropy penalty from a floppy host · Good heat with bad total points at lost freedom, not bad contacts.
  6. Sensitive optical signals at low concentration · Strong binders saturate early, so watch them dilute with optics.
  7. False · The constant lives in the curve shape, not in one point.
  8. Preorganise the host to cut the entropy penalty · Heat is already won; the freedom bill is what holds K down.
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