Aldehydes and Ketones - Problem Set Review

May 28, 2024

Lecture Notes: Aldehydes and Ketones - Problem Set Review

Problem 1: Carbonyl Group Properties

  • Identify the false statement about carbonyl:
    • (A) Carbonyl carbon is electrophilic - True
    • (B) Carbonyl oxygen is electron withdrawing - True
    • (C) Resonance structure places positive charge on carbonyl carbon - True
    • (D) Pi electrons are mobile and are pulled toward the carbonyl carbon - False

Problem 2: Boiling Points of Compounds

  • Ordering compounds by increasing boiling point:
    • Compounds: Butane (alkane), Butanol (alcohol), Butanone (ketone)
    • Order:
      1. Butane (lowest boiling point)
      2. Butanone (higher boiling point due to dipole interactions)
      3. Butanol (highest boiling point due to hydrogen bonding) - Answer: B

Problem 3: Reaction Product Identification

  • Reaction: Ketone + 1 equivalent of primary alcohol
    • Product: Hemiketal (due to single equivalent of alcohol)
    • Answer: C

Problem 4: Ketone + Primary Amine Reaction

  • Reaction between ketone and primary amine results in Imine formation
    • Double bond between carbon and nitrogen
    • Answer: A

Problem 5: Oxidation Reaction

  • Reaction: Aldehyde + Potassium Permanganate
    • Product: Carboxylic Acid
    • Answer: B

Problem 6: Ketone + Lithium Aluminum Hydride Reaction

  • Lithium Aluminum Hydride reduces ketones to secondary alcohols
    • Answer: B

Problem 7: Aldehyde + Excess Ethanol Reaction

  • Reaction: Benzaldehyde with excess ethanol in presence of anhydrous HCl
    • Product: Acetal (due to two equivalents of alcohol)
    • Answer: D

Problem 8: Isolation Difficulty of Hemiacetals and Hemiketals

  • Reasons for instability:
    • Molecules are unstable
    • Hydroxy group is rapidly protonated and lost as water under acidic conditions
    • Answer: B (Statements 1 and 2)

Problem 9: Structure of Hemiacetal

  • Central carbon in hemiacetal is bonded to:
    • Hydrogen, Alkyl group, OH group, OR group
    • Answer: A

Problem 10: Major Product Formation - Aldehyde vs. Ketone

  • Reaction: Hydrogen Cyanide + Butyraldehyde vs. Ethyl Methyl Ketone
    • Aldehyde is more reactive towards nucleophiles
    • Major product: Aldehyde + Hydrogen Cyanide forms cyano-hydrin
    • Answer: A

Problem 11: Pyridinium Chlorochromate (PCC) Properties

  • PCC as an oxidant:
    • Forms aldehydes from primary alcohols
    • Oxidizes secondary alcohols to ketones
    • Answer: C (Statements 1 and 3)

Problem 12: Formation of Geminal Diol

  • Hydration reaction: Water adds to carbonyl forming geminal diol
    • Answer: B (Water)

Problem 13: Ammonia + Aldehyde Reaction

  • Reaction: Ammonia + Glutaraldehyde
    • Product: Imine (carbon double bonded to nitrogen)
    • Answer: A

Problem 14: Ketone to Secondary Alcohol Reduction

  • Reducing Agent: Lithium Aluminum Hydride (LiAlH₄)
    • Answer: C

Problem 15: Enamine Formation

  • Tautomerization of imines results in enamine formation
    • Answer: D