Organic Chemistry I — High-Yield Review

Highest-Yield Facts

• High yield: Formal charge = valence − (lone-pair e⁻ + ½ bonding e⁻); use it to choose the best Lewis/resonance structure.
• High yield: ARIO ranks acidity: Atom → Resonance → Induction → Orbital (hybridization).
• High yield: sp³ = tetrahedral (109.5°), sp² = trigonal planar (120°), sp = linear (180°).
• High yield: Resonance stabilizes by delocalizing charge; more valid contributors = more stable.
• High yield: R/S via CIP priorities; a meso compound has an internal plane of symmetry and is achiral despite stereocenters; max stereoisomers = 2ⁿ (upper bound).
• High yield: SN2 = bimolecular, backside attack, inversion, favored by strong nucleophile/aprotic solvent, methyl/primary substrate. SN1 = unimolecular, carbocation, racemization, favored by protic solvent, tertiary substrate.
• High yield: E2 = anti-periplanar, strong base, Zaitsev (or Hofmann with bulky base). E1 competes with SN1.
• High yield: Markovnikov: H adds to less-substituted carbon (more stable carbocation). Anti- Markovnikov (HBr/peroxides) = radical mechanism.
• High yield: Alkene stability increases with substitution (hyperconjugation); heat of hydrogenation measures it.
• High yield: Electrophilic addition = carbocation (Markovnikov, rearrangements) vs halonium (anti addition, no rearrangements).
• High yield: Hydroboration-oxidation = anti-Markovnikov, syn; oxymercuration-demercuration = Markovnikov, no rearrangement.
• High yield: Terminal alkynes are acidic → acetylide ions → carbon-carbon bond formation (SN2).
• High yield: Radical stability mirrors carbocation stability; NBS brominates allylic positions.

Comparison Tables

Cumulative Self-Check (20 questions)

1. What is the formal charge on a nitrogen with 4 bonds and no lone pairs?
2. List ARIO in order.
3. What geometry and bond angle does sp² hybridization give?
4. Define a meso compound.
5. What is the maximum number of stereoisomers for a molecule with n stereocenters?
6. Which mechanism proceeds with inversion of configuration?
7. Which intermediate forms in SN1?
8. What geometry does E2 require?
9. State Markovnikov's rule.
10. Which reagent gives anti-Markovnikov hydration of alkenes?
11. What does hydroboration-oxidation's stereochemistry (syn) mean?
12. Why is a terminal alkyne acidic?
13. What does NBS do?
14. Which mechanism is favored by a polar aprotic solvent?
15. Differentiate kinetic from thermodynamic control.
16. What is hyperconjugation?
17. What is the difference between a nucleophile and an electrophile?
18. What does a curved double-headed arrow represent?
19. What is retrosynthesis?
20. Why don't rearrangements occur in halohydrin formation?

Answers and Rationales

1. +1 (valence 5 − (0 + 4) = +1).
2. Atom → Resonance → Induction → Orbital.
3. Trigonal planar, 120°.
4. An achiral molecule with an internal plane of symmetry despite stereocenters.
5. 2ⁿ (a maximum, reduced by meso/symmetry).
6. SN2.
7. A carbocation.
8. Anti-periplanar (H and leaving group coplanar and opposite).
9. H adds to the less-substituted carbon (more stable carbocation).
10. Hydroboration-oxidation.
11. H and OH add to the same face.
12. The sp C–H is more acidic (sp hybridization stabilizes the anion).
13. Allylic/benzylic radical bromination.
14. SN2 (aprotic solvents don't solvate the nucleophile).
15. Kinetic = fastest product; thermodynamic = most stable product.
16. Electron donation from adjacent σ C–H bonds into an empty p orbital.
17. Nucleophile = electron-pair donor; electrophile = electron-pair acceptor.
18. Movement of an electron pair.
19. Backward planning from a target molecule to simple starting materials.
20. The halonium ion is bridged (no carbocation forms).

Last-Minute Review

• Structure/bonding: formal charge, resonance, hybridization, ARIO, pKa.
• Stereochemistry: chirality, R/S (CIP), enantiomers/diastereomers/meso, Fischer projections.
• Reactivity: kinetics vs thermodynamics, carbocation/radical stability, arrow pushing.
• Substitution/elimination: SN1/SN2/E1/E2 decision framework; regiochemistry/stereochemistry.
• Alkenes/alkynes: Markovnikov, halonium (anti), hydroboration (syn/anti-Markovnikov), ozonolysis, hydrogenation, acetylide alkylation.
• Radicals: chain mechanisms, NBS allylic bromination, HBr/peroxide anti-Markovnikov.
• Synthesis: retrosynthesis, disconnection, forward-check.

Related

• Subject overview
• Topic 06 — Structure-Acidity Relationships: ARIO
• Topic 24 — Predicting SN1, SN2, E1, and E2 Products
• Topic 41 — Retrosynthetic Analysis