Chapter 22 — Quiz
Twenty-five questions on substituent effects in EAS. Answers and brief explanations follow.
1. -NH₂ is: (a) activating, ortho/para-directing (b) deactivating, ortho/para-directing (c) activating, meta-directing (d) deactivating, meta-directing
2. -NO₂ is: (a) activating, ortho/para-directing (b) deactivating, ortho/para-directing (c) activating, meta-directing (d) deactivating, meta-directing
3. -Cl is: (a) strongly activating, ortho/para-directing (b) weakly deactivating, ortho/para-directing (c) weakly deactivating, meta-directing (d) strongly deactivating, meta-directing
4. -COOH is: (a) activating, ortho/para-directing (b) deactivating, ortho/para-directing (c) activating, meta-directing (d) deactivating, meta-directing
5. -CH₃ (alkyl) is: (a) weakly activating, ortho/para-directing (b) weakly deactivating, ortho/para-directing (c) strongly activating, meta-directing (d) deactivating, meta-directing
6. An ortho/para-director generally works by: (a) donating electrons to the 2,4,6 ring carbons (where positive charge would go in the o/p arenium) (b) withdrawing electrons from the 3 and 5 positions (c) directly bonding to the electrophile (d) destabilizing the meta arenium only
7. A meta-director generally works by: (a) destabilizing the o/p arenium more than the meta arenium (b) stabilizing the meta arenium directly (c) donating into the 2,4,6 positions (d) being a good leaving group
8. Halogens are unique because they: (a) activate AND direct meta (b) deactivate AND direct ortho/para (c) activate AND direct ortho/para (d) deactivate AND direct meta
9. Why is halogen ortho/para-directing despite being electron-withdrawing? (a) Halogens have lone pairs that can donate by resonance to the o/p arenium (b) The halogen acts as a Lewis base (c) Halogens are weakly π-donors in the ground state (d) The halogen literally bonds to the electrophile
10. The strongest activator listed: (a) -CH₃ (b) -OH (c) -O⁻ (d) -OCH₃
11. The strongest deactivator listed: (a) -COOR (b) -NO₂ (c) -CN (d) -CHO
12. Why does -NH₃⁺ (protonated amine) direct meta, while -NH₂ directs ortho/para? (a) The protonated form has no lone pair on N; it acts as a pure σ-acceptor (like an alkylammonium); meta-directing (b) The N lone pair is hidden by the proton; thus it is no longer a π-donor; meta-directing (c) Both (a) and (b) describe the same phenomenon; correct (d) The protonation reverses every aspect of the substituent
13. When -OCH₃ (anisole) is brominated, the major product is: (a) ortho-bromoanisole (b) meta-bromoanisole (c) para-bromoanisole (very strongly preferred) (d) a 1:1:1 mix
14. When toluene is brominated, the para:ortho ratio is roughly: (a) 99:1 (b) 60:40 (c) 25:75 (d) 10:90
15. Why does anisole give more para selectivity than toluene? (a) Methoxyl is a much stronger activator than methyl (resonance donation), so the electronic preference (para) overwhelms statistical (ortho) effects (b) Anisole is sterically smaller than toluene (c) Anisole has 2 equivalent positions (para is unique); toluene has 4 (d) None of the above
16. A reaction with Hammett ρ = +2.5 has a transition state that: (a) builds up positive charge on the ring (favored by donors) (b) builds up negative charge on the ring (favored by acceptors) (c) is cation-stabilizing (d) does not depend on substituent at all
17. The Hammett ρ for EAS bromination is approximately: (a) +2 (b) -2 (c) -12 (very negative) (d) 0
18. A pharmaceutical chemist wants to make 3-bromobenzoic acid. The correct order is: (a) brominate first, then convert ring carbon to -COOH (b) install -COOH first (via FC acylation + oxidation), then brominate (c) brominate first, then -COOH (because Br is o/p-directing and -COOH is meta-directing) (d) install -COOH first; that's meta-directing, so the next bromination goes meta
19. A pharmaceutical chemist wants to make 4-bromobenzoic acid. The correct order is: (a) brominate first, then -COOH (b) install -COOH first (so the next bromination goes meta — but wait, that's 3-bromo, not 4-bromo!) (c) brominate first (so next reaction goes ortho/para to Br = position 4 = para = correct) (d) Either order works
20. Aniline (Ph-NH₂) is: (a) very reactive in EAS — too reactive to control (b) so reactive it is hard to mono-substitute (c) typically protected as acetanilide (PhNHCOCH₃) before EAS (d) all of the above
21. Why is the amine protected as an amide before nitration? (a) The free amine would be protonated by H₂SO₄, becoming -NH₃⁺ (meta-directing) — wrong product (b) The amide is less activating, so reaction is more controlled (c) Both (a) and (b) (d) Protection is unnecessary
22. Acetanilide (PhNHCOCH₃) directs: (a) meta (b) ortho/para (still!) (c) randomly (d) only para
23. Diazonium salt Ar-N₂⁺ + CuCl gives: (a) Ar-Cl (Sandmeyer reaction) (b) Ar-Br (c) Ar-OH (d) Ar-CN
24. A diazonium salt at high temperature in water gives: (a) Ar-OH (hydrolysis of diazonium) (b) Ar-N₂⁺ stable (c) Ar-NH₂ (d) decomposes to anything
25. "Two existing substituents that direct to the same position" is called: (a) Reinforcing (cooperative) — predict the product confidently (b) Conflicting (competing) — the stronger activator wins (c) Reinforcing (cooperative); predict the product confidently — the answer (d) None of the above is the right phrase
Answer Key
| # | Answer | Explanation |
|---|---|---|
| 1 | a | -NH₂: π-donor; both activates and o/p-directs |
| 2 | d | -NO₂: π-acceptor (also σ-acceptor); deactivates and meta-directs |
| 3 | b | Cl: deactivates (σ) but o/p-directs (π) |
| 4 | d | -COOH: π-acceptor; deactivates, meta-directs |
| 5 | a | -CH₃: weak π-donor (hyperconjugation/inductive); activates, o/p |
| 6 | a | o/p-directors stabilize the o/p arenium where positive charge is on 2,4,6 |
| 7 | a | meta-directors destabilize the o/p arenium more than the meta one |
| 8 | b | Halogens uniquely deactivate AND o/p-direct |
| 9 | a | Lone pair on halogen can resonance-donate to the o/p arenium |
| 10 | c | -O⁻ > -OH > -OCH₃ > -CH₃ (lone pair availability) |
| 11 | b | -NO₂ is the textbook strongest deactivator |
| 12 | c | Protonation removes the lone pair → no π-donation → meta |
| 13 | c | Anisole is very para-selective (>90%) |
| 14 | b | Toluene is moderately para-selective (~60:40) |
| 15 | a | Stronger π-donation amplifies regiochemical preference |
| 16 | b | Positive ρ → builds up negative charge → favored by acceptors (e.g., saponification) |
| 17 | c | EAS is highly substituent-sensitive; ρ ≈ -12 |
| 18 | d | -COOH first; it's meta-directing; next bromination goes meta = 3-bromo |
| 19 | c | Brominate first; Br is o/p-directing; -COOH installed via FC + oxidation goes para to Br |
| 20 | d | Aniline is very reactive; usually protected |
| 21 | c | Both reasons apply |
| 22 | b | Acetanilide is still o/p-directing (slightly weaker than free amine) |
| 23 | a | Sandmeyer with CuCl gives aryl chloride |
| 24 | a | Aqueous hydrolysis of diazonium → phenol (Ar-OH) |
| 25 | c | Reinforcing direction; predict confidently |
Concept connections
- Inductive vs resonance: most o/p-directors are resonance donors (-NH₂, -OH, -OCH₃) or weak σ donors (-CH₃); most meta-directors are σ + π acceptors (-NO₂, -CN, -COOR).
- Halogens: the exception that proves the rule. Inductive (deactivating) wins on rate; resonance (lone pair donation) wins on regiochemistry.
- Order matters in synthesis: install the o/p-director first (to put a substituent at o/p) or the meta-director first (to put a substituent meta). Plan retrosynthetically.