Organic Chemistry 2 Practice Tests: Multiple Choice Review

Question 1: Major Product of Reaction with Aldehyde and Silver Oxide

• Key points: Tollen's Reagent (Ag⁺, as silver oxide or complexed with ammonia) oxidizes aldehydes to carboxylic acids.
• Elimination based on functionality:
  • A = Not an aldehyde
  • C = Ketone (doesn't fit unless there's an alpha-hydroxy)
  • B and D (protonated vs deprotonated forms of carboxylic acid):
    • Under acidic conditions (H₃O⁺), carboxylic acid will be in its protonated form (B) => Answer is B

Question 2: Bromination Reaction with 1-Ethyl-4-Isopropyl Benzene

• Key points: Radical bromination in presence of UV light replaces benzylic hydrogen.
• Steps and elimination:
  • B and D won't work (no Lewis acid catalyst like FeBr₃).
  • Reactivity comparison between secondary and tertiary radicals:
    • Tertiary radical is more stable.
    • Answer is C (bromine replaces tertiary hydrogen).

Question 3: Proton with the Lowest pKa

• Steps and elimination:
  • Between two carbonyl groups have pKa around 9. Alone pKa ~20
  • More acidic hydrogen: carboxylic acid (pKa ~4-5).
  • Comparison:
    • Carboxylic acid wins => Protons on carboxylic acid have lowest pKa. Answer is D.

Question 4: IR Spectrum Analysis

• Key signals:
  • Broad peak (2500-3300) ➜ Carboxylic acid (OH stretch).
  • 1700 cm⁻¹ band ➜ Carbonyl stretch.
  • CO stretch around 1200 cm⁻¹
  • 2200 cm⁻¹ ➜ Alkyne or nitrile (we have an alkyne)
  • Choices:
    • Answer is B (carboxylic acid + alkyne).**

Question 5: Para-Nitrobenzoic Acid from Benzene

• Based on directing effects:
  • Nitration first, oxidation later (Meta-directing).
  • Para orientation necessary, meta-directing groups to be avoided.
  • Correct order and catalyst timing: Answer A (alkylate first, nitration later, ensures para-orientation).

Question 6: Reaction for Ester Formation from Acid Chloride

• Review Grignard, Gilman reagents, and alcohols:
  • Grignard ➜ Alcohol (not ester).
  • Gilman ➜ Ketone.
  • Alcohol + Acid chloride ➜ Ester.
  • Correct reagent: Alcohol (C).

Question 7: Conversion using PCC and Vedic Reaction

• Steps:
  • PCC (oxidizes secondary alcohol to ketone).
  • Analysis of reagent influence on structure (alkyl halide, PPh₃, BuLi): forms an alkene via Wittig reaction.
  • Outcome: Vedic reaction gives longer side chain.
  • Answer is D (correct chain order and formation).

Question 8: Diels-Alder Cycloaddition Identification

• Reverse-identifying: count carbons and ring formation
  • Eliminate based on carbon number.
  • Analysis: Seven carbons (B fits). starts with ring form gives bicyclic product. Answer is B.**

Question 9: Intramolecular Aldol Reaction with Cyclohexane-dione

• Concept: Aldol condensation and its products (beta-hydroxy or alpha-beta unsaturated keto)
  • Correct alpha carbon identification, correct dehydration setup.
  • Heat-driven dehydration ➜ double bond formation.
  • Answer is C (correct double bond conjugation).

Question 10: Alpha Hydrogen Replacement with Methyl Group

• Analyzing base choice and temperature:
  • LDA vs Sodium Hydride (bulky vs small): kinetic vs thermodynamic control.
  • Low temperature favors kinetic product.
  • High temperature and small base for thermodynamic product.
  • Answer: LDA and low temperature indicate kinetic control ➜ Answer A.

Question 11: Activation and Directing Effects Challenges

• Ring with more activation reacts better:
  • Strongly activating groups (propyl group placement).
  • Directing of bromine placement relative to strong activators.
  • Answer: Bromine positions ortho to highly activating alkoxy group => B.

Question 12: H NMR Spectrum Signals

• Identify unique hydrogen environments:
  • Base on symmetry and chemical environment.
  • Analysis of signals (hydrogen positions).
  • Answer: D (compounds 2 and 3 provide 2 distinctive H NMR signals).

Question 13: Reacting with Ketone to Yield Imines/Enamines

• Determining major product via nucleophilicity:
  • Amine attacks forming Imine or Enamine based on primary or secondary amine.
  • Answer: Primary amine gives Imine => Answer A.

Question 14: Aromaticity Criteria

• Hückel’s rule (4n+2) for π electrons, delocalization via sp² hybridization:
  • Identify non-aromatic compounds by disqualifying hybridization and/or electron count.
  • Answer: D (sp³ hybridized prevents full conjugation => non-aromatic).

Question 15: H NMR Spectrum and Functional Groups

• Discount based on apparent signals:
  • Aldehyde (9-10), benzene (6.5-8.5), aliphatic CH (varied based on bonding).
  • Correct functional placement relative to chemical shifts.
  • Proper assignment of spin splitting:
  • Answer: D fits consistent shifts and structures (2 quartets, triplet): => matches functional groups given.