MCAT Organic Chemistry Question 23: Answer and Explanation
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Question: 23
8. (+)-glyceraldehyde and (–)-glyceraldehyde refer to the (R) and (S) forms of 2,3-dihydroxypropanal, respectively. These molecules are considered:
- A. enantiomers.
- B. diastereomers.
- C. meso compounds.
- D. structural isomers.
Correct Answer: A
Explanation:
(+)-glyceraldehyde and (–)-glyceraldehyde, or (R)- and (S)-2,3-dihydroxypropanol, are enantiomers. Enantiomers are nonsuperimposable mirror images. Each has only one chiral center (C-2), which has opposite absolute configuration in these two molecules.