Directing Effects in Electrophilic Aromatic Substitution · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Who steers the next group on a benzene ring

Science · Chemistry · ages 20-22
Name ______________________   Date ____________

  1. An NO2 group sits on a benzene ring. Where does the next group land?

    • At the ortho or para spots
    • At every spot with equal ease
    • At the meta spot

  2. An OH group sits on a benzene ring. Where does the next group land?

    • At the ortho or para spots
    • At the meta spot only
    • At every spot with equal ease

  3. A chlorine atom on a benzene ring speeds the ring up and directs newcomers to the meta spot.

    Circle one:   True   False

  4. For phenol, why is ortho attack favoured over meta attack?

    • Ortho attack avoids the intermediate entirely
    • One resonance form puts the positive charge next to the oxygen lone pair, which steadies it
    • Meta attack gives more resonance forms than ortho attack

  5. Why does a halogen direct ortho and para even though it slows the ring?

    • Its lone pairs steady the intermediate by resonance on those routes
    • It donates protons to the ring on those routes
    • It blocks the meta spot with its large size

  6. You need to put a bromine meta to an amino group on benzene. What must you handle first?

    • Bromine must be installed before anything else is done
    • The amino group must be protected before further steps
    • Nothing, since amino groups never disturb later steps

  7. A student plans a Friedel Crafts alkylation on a ring carrying an NO2 group. What is wrong with the plan?

    • Nothing is wrong, since every ring accepts Friedel Crafts steps
    • The nitro group must be removed before any substitution can happen
    • Friedel Crafts reactions fail on strongly deactivated rings such as this one

  8. To make meta bromonitrobenzene from benzene, which order of steps works and why?

    • Nitrate first, then brominate, since the nitro group steers the next group meta
    • Brominate first, then nitrate, since bromine steers the next group meta
    • Either order works, since the two groups never steer each other
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Answer key

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

Who steers the next group on a benzene ring W1-mt_KMRxS6s06f-s1

  1. At the meta spot · NO2 pulls electrons away, which destabilises the ortho and para routes and leaves meta.
  2. At the ortho or para spots · OH pushes electrons into the ring, which favours attack at the ortho and para spots.
  3. False · Chlorine slows the ring down yet still directs ortho and para, which makes it the classic exception.
  4. One resonance form puts the positive charge next to the oxygen lone pair, which steadies it · No matching form exists for meta attack, so comparing the forms settles the outcome.
  5. Its lone pairs steady the intermediate by resonance on those routes · Resonance from the lone pairs steadies the arenium ion for ortho and para attack only.
  6. The amino group must be protected before further steps · A free amino group is easily oxidised and dominates direction, so it is protected before nitration and similar steps.
  7. Friedel Crafts reactions fail on strongly deactivated rings such as this one · Strong deactivation shuts down Friedel Crafts chemistry, so a different route is needed.
  8. Nitrate first, then brominate, since the nitro group steers the next group meta · NO2 is a meta director, so installing it first steers bromine into the wanted spot.
Worksheet · LightMySky