Thalidomide Kembar Berbahaya |Enantiomer | Stereokimia 2 | Kuliah Online | Kimia Organik

Summary

This video lecture dives into the concept of enantiomers, starting with the historical discovery of optical activity by biotin and Louis Pasteur. It explores how enantiomers, mirror-image molecules that are non-superimposable, play a significant role in chemistry and biology. The lecture discusses how enantiomers can affect properties like optical rotation, their relevance in drug effects (such as thalidomide), and their different interactions with the human body. The video also covers methods to distinguish between enantiomers using stereochemistry systems like RS and introduces concepts like enantiomeric excess and diastereomers.

Takeaways

• 😀 Thalidomide, initially used as an anti-nausea medication for pregnant women in the 1960s, gained notoriety due to its teratogenic effects, leading to birth defects.
• 😀 Enantiomers are molecules that are non-superimposable mirror images of each other, such as the example of alanine, a common amino acid in proteins.
• 😀 The discovery of optical activity in substances like sugar and camphor by Biot and Pasteur paved the way for understanding optical isomers and their behavior.
• 😀 Louis Pasteur's work on tartaric acid crystals demonstrated the concept of enantiomers, showing that two mirror-image crystals could rotate polarized light in opposite directions.
• 😀 Enantiomers have the same physical and chemical properties but differ in their ability to rotate polarized light, with one being dextrorotatory (+) and the other levorotatory (-).
• 😀 The RS system is used to distinguish between enantiomers by assigning priorities to substituents around a chiral center, helping to define whether a molecule is in the R or S configuration.
• 😀 A molecule with the configuration 'R' has a clockwise rotation, while 'S' has a counterclockwise rotation, determined by the sequence of priorities of substituents around the chiral center.
• 😀 Enantiomeric excess (EE) quantifies the proportion of one enantiomer in a mixture, with higher values indicating a predominance of one form over the other.
• 😀 The physical properties of enantiomers, such as optical activity, can be used to differentiate them, but they require careful experimental setup to ensure accurate measurements.
• 😀 In pharmaceutical contexts, different enantiomers of a drug can have vastly different biological effects, with one enantiomer being therapeutic and the other potentially harmful, as shown by thalidomide and naproxen.

Q & A

What is thalidomide and why is it significant in the 1960s?

Thalidomide was a medication used as an anti-nausea treatment for pregnant women. It became infamous in the 1960s not because of its intended effects but due to its teratogenic effects, which caused birth defects in babies. This led to the drug being banned.

Who discovered optical activity and what does it mean?

The French chemist Louis Pasteur discovered optical activity, the ability of certain substances, such as sugar and camphor, to rotate the plane of polarized light when passed through them. This property is characteristic of optically active compounds.

What are enantiomers, and how are they related to chiral molecules?

Enantiomers are pairs of molecules that are non-superimposable mirror images of each other. They are a type of stereoisomer and are typically associated with chiral molecules, which have a carbon atom bonded to four different groups.

What is the historical significance of Pasteur's discovery of enantiomers?

Louis Pasteur's discovery that two crystals of tartaric acid could rotate polarized light in opposite directions laid the foundation for the concept of enantiomers. This discovery was a significant step in understanding stereochemistry and molecular chirality.

How does one determine the configuration of enantiomers using the RS system?

To determine the configuration of enantiomers using the RS system, the groups attached to the chiral carbon are ranked by atomic number. The molecule is then oriented such that the lowest priority group is positioned away from the viewer, and the configuration is determined by the direction of the rotation from the highest to the lowest priority.

What is the difference between dextrorotatory and levorotatory substances?

Dextrorotatory substances rotate polarized light to the right, while levorotatory substances rotate polarized light to the left. These terms describe the optical activity of a substance and are not related to the molecule's RS configuration.

What is enantiomeric excess (EE) and how is it calculated?

Enantiomeric excess (EE) refers to the difference in the amount of each enantiomer in a mixture. It is calculated as the absolute difference in the percentages of the two enantiomers, for example, a 75%/25% mixture would have an EE of 50%.

What impact does the configuration of a molecule have on its biological activity?

The configuration of a molecule, such as its enantiomeric form, can significantly affect its biological activity. For example, one enantiomer of a drug may be therapeutic, while its mirror image could be toxic or ineffective.

How can enantiomers be separated for commercial purposes?

Enantiomers can be separated by converting them into diastereomers, which have different physical properties and can be separated using traditional methods like crystallization or chromatography.

What is the significance of thalidomide's enantiomers in its toxicity?

Thalidomide's teratogenic effects were caused by one of its enantiomers, while the other enantiomer did not produce such effects. This illustrates how different enantiomers of a molecule can have drastically different biological effects.