March 1, 2012 Issue

Physics To Go 122 - Mirror image molecules

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Physics in Your World

Structure and Optical Isomerism image
image credit: NASA; image source;  larger image

Structure and Optical Isomerism

Have you noticed that the left hand is the mirror image of the right hand, but they cannot be superimposed? That's also true for some molecules containing carbon atoms. In the image above, the molecule on the left cannot be superimposed on the one on the right.

To learn more about such molecules, check out Structure and Optical Isomerism.

Such left-handed and right-handed molecules rotate the plane of polarization of light in opposite directions. To find out more about polarized light and this important effect, click here. Also, you can learn how Louis Pasteur explained it.

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Physics at Home

Rotating Light

Right-and left-handed molecules were discovered because their solutions have the opposite effect on polarized light. For a related effect, try the famous Karo® syrup demonstration, as described in this Exploratorium activity. To see the demo, check out this YouTube video.


From Physics Research

Electronic Handedness in Copper-Silver Combo image
image credit:   A. Mugarza, C. Krull, S. Stepanow, G. Ceballos, and P. Gambardella,  CIN2; image source; larger image

Electronic Handedness in Copper-Silver Combo

Notice how the two images above have opposite handedness? These images show electronic properties of a small layer of copper on top of silver, but neither silver nor copper have any handedness themselves. To learn more, visit this American Physical Society webpage.

(This feature was updated on September 21, 2013.)

Worth a Look

Molecular Chirality

Both amino acid molecules (the building blocks of proteins) and sugars can be right- or left-handed, and the way they react chemically depends on their handedness. To find out how handedness is important in our diet, and in drugs, visit Molecular Chirality.

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