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Organic Chemistry 2 · High-yield review

Organic Chemistry II — High-Yield Review

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On this page 2 sections
  1. In 30 seconds
  2. The college version

In 30 seconds

A condensed, exam-focused review of all 33 topics. Use after working through the topic files.

The college version

Highest-Yield Facts

  • High yield: Degree of unsaturation = (2C + 2 + N − H − X)/2.
  • High yield: IR diagnostic absorptions: O-H ~3200–3600 (broad), C=O ~1680–1750, C≡N ~2250.
  • High yield: ¹H NMR: n+1 splitting, integration = proton count, chemical shift (deshielded = downfield).
  • High yield: Hückel's rule: 4n+2 π electrons, planar, cyclic, fully conjugated → aromatic.
  • High yield: EAS directing effects: activating groups = ortho/para; deactivating = meta (halogens are deactivating but ortho/para).
  • High yield: Nucleophilic addition (aldehydes/ketones) vs nucleophilic acyl substitution (acid derivatives, with leaving group).
  • High yield: Reactivity ladder: acid chloride > anhydride > ester > amide > carboxylate.
  • High yield: Aldol = enolate + aldehyde/ketone → β-hydroxy carbonyl; dehydration → α,β-unsaturated.
  • High yield: Claisen = ester enolate → β-keto ester; Dieckmann = intramolecular.
  • High yield: Michael addition = 1,4-addition to α,β-unsaturated carbonyl; Robinson annulation = Michael + intramolecular aldol.
  • High yield: Kinetic vs thermodynamic enolate (LDA = kinetic, less-substituted).
  • High yield: Acetal/ketal = protecting group for carbonyls; hemiacetal → acetal.
  • High yield: Grignard/organolithium add to carbonyls (C–C bond formation), react with epoxides.
  • High yield: Amines: Hofmann elimination = least-substituted alkene (anti-Zaitsev); Gabriel synthesis = primary amine.
  • High yield: Suzuki/Heck/Stille/Sonogashira = Pd-catalyzed cross-coupling (C–C bond formation).

Comparison Tables

Do not confuseWithDifference
IRNMRFunctional groups vs atom connectivity/environment
Chemical shiftIntegrationEnvironment (ppm) vs proton count
AromaticAntiaromatic4n+2 vs 4n π electrons
EASSNArElectrophilic (ring) vs nucleophilic (leaving group)
Nucleophilic additionAcyl substitutionNo leaving group vs with leaving group
EnolEnolateNeutral tautomer vs anionic nucleophile
Kinetic enolateThermodynamic enolateLess-substituted/fast vs more-substituted/stable
1,2-addition1,4-additionDirect carbonyl vs conjugate (β-carbon)
AldolClaisenAldehyde/ketone vs ester (β-keto ester)
AnomerEpimerAnomeric carbon vs any stereocenter

Cumulative Self-Check (20 questions)

  1. Write the degree-of-unsaturation formula.
  2. What does a broad IR absorption near 3300 cm⁻¹ suggest?
  3. State the n+1 rule.
  4. State Hückel's rule.
  5. Are halogens ortho/para or meta directors?
  6. Differentiate nucleophilic addition from acyl substitution.
  7. Order acid derivatives by reactivity (most to least).
  8. What is the product of an aldol condensation after dehydration?
  9. What does a Claisen condensation produce?
  10. What is a Michael addition?
  11. Which reagent gives the kinetic (less-substituted) enolate?
  12. What are acetals used for?
  13. What does the Wittig reaction accomplish?
  14. Name two Grignard-type reagents.
  15. What is the Hofmann elimination product?
  16. What does the Gabriel synthesis give?
  17. Name one Pd-catalyzed cross-coupling reaction.
  18. Differentiate an enol from an enolate.
  19. What is a hemiacetal?
  20. What is the Baeyer-Villiger oxidation product?

Answers and Rationales

  1. (2C + 2 + N − H − X)/2.
  2. O-H or N-H stretch.
  3. A proton with n neighbors gives n+1 peaks.
  4. 4n+2 π electrons, planar, cyclic, fully conjugated → aromatic.
  5. Ortho/para (but deactivating).
  6. Addition = no leaving group; acyl substitution = leaving group departs.
  7. Acid chloride > anhydride > ester > amide > carboxylate.
  8. An α,β-unsaturated carbonyl compound.
  9. A β-keto ester.
  10. 1,4-conjugate addition to an α,β-unsaturated carbonyl.
  11. LDA (low temperature, kinetic conditions).
  12. Protecting carbonyls from nucleophiles.
  13. Converts a carbonyl to an alkene.
  14. Grignard (RMgX) and organolithium (RLi).
  15. The least-substituted (anti-Zaitsev) alkene.
  16. A primary amine.
  17. Suzuki, Heck, Stille, or Sonogashira.
  18. Enol = neutral tautomer; enolate = deprotonated anionic nucleophile.
  19. The addition product of an alcohol to a carbonyl (one -OR, one -OH).
  20. Converts a ketone to an ester (aldehyde to carboxylic acid).

Last-Minute Review

  • Spectroscopy: degree of unsaturation, MS (M+, isotope patterns), IR (functional groups), NMR (n+1, integration, chemical shift).
  • Aromaticity/substitution: Hückel, EAS directing effects, SNAr vs benzyne.
  • Carbonyl: nucleophilic addition (acetals, imines, Grignard), acyl substitution (reactivity ladder), Wittig, Baeyer-Villiger.
  • Enolates: aldol, Claisen, alkylation, Michael, Robinson annulation, kinetic vs thermodynamic.
  • Amines: Hofmann elimination, Gabriel synthesis, reductive amination, diazonium.
  • Biomolecules: carbohydrates (anomers, mutarotation), amino acids (zwitterions, pI), lipids.

Related

  • Subject overview
  • Topic 03 — Nuclear Magnetic Resonance Spectroscopy
  • Topic 12 — Electrophilic Aromatic Substitution
  • Topic 23 — Aldol Reactions

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