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Organic Chemistry Flashcards

7 cards from real MCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which amino acid side chain contains a thiol group that can form disulfide bonds?

    Answer: Cysteine

    Cysteine contains a –SH (thiol) group that can be oxidized to form disulfide bonds (–S–S–) important for protein tertiary and quaternary structure.

  2. When 2-methylpropene reacts with HBr, the major product is 2-bromo-2-methylpropane rather than 1-bromo-2-methylpropane. This illustrates:

    Answer: Markovnikov's rule

    Markovnikov's rule predicts that the electrophile (H⁺) adds to the less substituted carbon, placing the nucleophile (Br⁻) on the more substituted (more stable carbocation) carbon.

  3. What is the stereochemical outcome of an SN2 reaction?

    Answer: Inversion of configuration (Walden inversion)

    SN2 proceeds via a backside attack transition state, resulting in inversion of configuration at the chiral center (Walden inversion).

  4. Which of the following is the strongest acid?

    Answer: CH3COOH (pKa ≈ 4.75)

    Acetic acid (pKa ≈ 4.75) is the strongest acid listed because resonance stabilization of the acetate anion greatly lowers the pKa compared to alcohols or phenols.

  5. A compound gives a positive Tollens' test (silver mirror) but does not react with Fehling's solution. Which compound is most likely?

    Answer: Benzaldehyde

    Benzaldehyde is oxidized by Tollens' reagent (silver mirror) but its product is insoluble in Fehling's solution (copper-based), which requires water-soluble reducing sugars.

  6. In NMR spectroscopy, which proton environment would appear at the highest chemical shift (most downfield)?

    Answer: –CHO (aldehyde proton)

    Aldehyde protons (–CHO) resonate at δ 9–10 ppm, far downfield due to both deshielding by the electronegative oxygen and the anisotropy of the carbonyl.

  7. Which reaction mechanism involves a radical chain process initiated by heat or light?

    Answer: Free radical halogenation of alkanes

    Free radical halogenation involves initiation (homolytic cleavage by heat or light), propagation (chain steps), and termination, characteristic of radical chain mechanisms.