Chirality: molecule and mirror image
About this app
L-alanine and its mirror image as rotatable ball-and-stick models: superimposed, H and CH₃ remain swapped, while glycine with two H matches. A binding pocket with three sites holds L-alanine at three sites and D-alanine at only two. Plus R- and S-carvone (spearmint and caraway).
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
What it is about
A carbon atom with four different partners is called a stereocentre. Such a molecule exists in two forms that behave like an image and its mirror image and cannot be superimposed by any rotation, just like left and right hands. These forms are called enantiomers, and the property is chirality. Enantiomers have the same melting and boiling points but behave differently towards other chiral molecules. Enzymes and receptors are built from L-amino acids and can therefore tell image and mirror image apart, for example in smell or in the effect of a drug.
What the app shows
L-alanine stands as a ball-and-stick model in CPK colours in front of a mirror plane, with its mirror image D-alanine behind it. When superimposed, the amino and carboxyl groups coincide, but hydrogen and methyl remain swapped. Glycine with two hydrogens, by contrast, matches its mirror image completely. A binding pocket with three hollows shows the three-point model: L-alanine fits at three sites, D-alanine at only two. A third scenario shows R-carvone and S-carvone, which smell of spearmint and of caraway.
Try it yourself
Drag in the scene to view the molecules from all sides and try to make the mirror image match by rotating it. Then superimpose the two and compare with glycine. In the receptor you switch between L- and D-alanine and push the molecule into the pocket. The findings panel states how many partners or sites match.
Frequently asked questions
- What is chirality in chemistry?
- A molecule is chiral if it cannot be superimposed on its mirror image. The most common reason is a carbon atom with four different partners, a stereocentre. The two forms are called enantiomers.
- Why is glycine not chiral?
- Glycine carries two hydrogen atoms on its central carbon. It therefore has only three different partners and no stereocentre. Its mirror image can be rotated to lie exactly on the original.
- Why do R-carvone and S-carvone smell different?
- Both consist of the same atoms with the same bonds and are mirror images. Olfactory receptors are themselves chiral and respond differently to the two forms: R-carvone smells of spearmint, S-carvone of caraway.
- What can I adjust in the app?
- You choose the mirror, receptor or carvone scenario, switch between alanine and glycine or between L- and D-alanine, superimpose image and mirror image, dock the molecule and rotate the scene freely.
Subject: Chemistry
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