Organic chemistryLesson 2 of 4 in the course Stereochemistry

Enantiomers: Chirality, Biological Effects, and Preparation

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Enantiomers are a key type of stereoisomer: molecules that have the same connections between atoms but differ in their three-dimensional arrangement. Understanding their relationship helps explain why some molecules interact differently with light, biological systems, and other chiral substances.

Enantiomers are a pair of molecular entities that are mirror images of each other but cannot be superimposed. A familiar analogy is a pair of hands: the left and right hands are mirror images, but no rotation of one hand makes it fit exactly over the other.

All flashcards

What is an enantiomer?
One member of a pair of molecular structures that are mirror images but cannot be superimposed.
What is a racemate?
A mixture containing equal amounts of two enantiomers. Their optical rotations cancel, leaving no net rotation.
What distinguishes a diastereomer from an enantiomer?
Diastereomers are stereoisomers that are not mirror images of one another; enantiomers are non-superposable mirror images.
What makes a compound meso?
It has stereogenic centers but is achiral because its symmetry, commonly an internal mirror plane, makes it superimposable on its mirror image.
What do R/S, (+)/(−), and D/L indicate?
R/S describes absolute configuration, (+)/(−) indicates the observed direction of optical rotation, and D/L describes a relationship to glyceraldehyde.

Quiz questions

  1. What is a chiral switch in medicine?Answer: Replacing a racemic medicine with a single-enantiomer version.
  2. What distinguishes enantioconvergent synthesis from simply separating a racemate?Answer: Both starting enantiomers can form the same desired product enantiomer.
  3. What does racemization do to a sample of an enantiomer?Answer: It interconverts enantiomers, producing a racemic mixture.
  4. What are quasi-enantiomers?Answer: Related molecular species that resemble mirror-image partners but are not exact mirror images.
  5. Why can two enantiomers of a compound have different biological effects?Answer: They can interact differently with chiral biological molecules.

Based on the Wikipedia article Enantiomer, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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