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Twists of Scent: How Mirror-Image Molecules Shape the World Around Us

Eeshan Banerjee

Imagine walking through a garden and smelling the strong sweet scent of blooming flowers. Now picture a lemon being sliced open, releasing its sharp and zingy fragrance as you cut through. What if I told you that the same molecule could smell like both flowers and lemons, depending on how it’s arranged?  This is the fascinating world of enantiomers—molecules that are mirror images of each other but often behave in remarkably different ways.


What Are Enantiomers?


To understand enantiomers, we need to look at chirality—a concept that simply refers to objects that cannot be superimposed on their mirror images. A common example is your hands as a representation for a pair of enantiomers. Hold your right hand in front of a mirror, and its reflection will look like your left hand. No matter how you twist or turn them, your left and right hands can never perfectly overlap. Enantiomers are molecules that behave in the same way: they are non-superimposable mirror images of each other, like left-handed and right-handed versions of the same structure.

Figure 1 - Example of Enantiomers with Lactic Acid  (Byju’s)


In chemistry, this small difference in molecular arrangement can have big consequences. Enantiomers share the same molecular formula and bonds with their main carbon atom, but because they are arranged differently in space, they interact differently with other molecules, including those in our bodies. This is particularly crucial in the world of pharmaceuticals.


Enantiomers in Medicine: The Right Fit Matters


An example of the presence of enantiomers is the drug thalidomide. In the 1950s, thalidomide was prescribed to pregnant women to treat morning sickness. Unfortunately, while one enantiomer of thalidomide helped reduce symptoms, the other caused severe birth defects of children. This highlighted the significance of understanding and controlling the chirality of molecules in drug processing. In today’s day, pharmaceutical companies rigorously examine enantiomers to ensure that only the desired version of a drug is administered, to avoid any harmful effects on their patients.


Figure 2 - Thalidomide Enantiomers (ResearchGate)


Enantiomers in Our Daily Lives


Enantiomers may be mirror images, but their effects can be worlds apart. From influencing the way we experience smells to shaping the effectiveness of medications, these stereoisomers have a far-reaching impact on our daily lives. The next time you smell the scene spearmint or reach for an aspirin, you’ll know that the hidden world of chirality is at work, demonstrating that even the smallest changes in molecular structure can lead to entirely different outcomes.


References


American Chemical Society. “Thalidomide.” American Chemical Society, 1 Sept. 2014, www.acs.org/molecule-of-the-week/archive/t/thalidomide.html. Accessed 26 Oct. 2024.


BYJUS. (n.d.) "Examples of Enantiomers - Detailed Explanation with FAQs.” BYJUS, byjus.com/chemistry/examples-of-enantiomers/. Accessed 26 Oct. 2024.


Publications, SAGE. “Figure 3. Thalidomide Interconverts between (R)- and (S)-Enantiomers...” ResearchGate, ResearchGate, Oct. 2011, www.researchgate.net/figure/Thalidomide-interconverts-between-R-and-S-enantiomers-with-protein-binding-of-55_fig3_236106954. Accessed 26 Oct. 2024.



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