MCAT Organic Chemistry Question 171: Answer and Explanation

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Question: 171

6. Four compounds, I, II, III, and IV, are separated by chromatographic techniques. Compound III is the most polar, II the least polar, and I and IV have intermediate polarity. The solvent system is 85:15 ethanol:methylene chloride. Which spot on the card below likely belongs to compound III?

  • A. A
  • B. B
  • C. C
  • D. D

Correct Answer: A

Explanation:

This is an example of reverse-phase chromatography. The solvent system is polar, which means that the most polar compound will travel the furthest up the card, resulting in the largest Rf. This gives compound III the largest Rf, which corresponds to spot A.

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