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A particular enantiomer can show affinity towards another enantiomer of another diasteromer eg. body receptors with chiral drugs, chiral stationary phase of chromatography etc.

But what's the reason behind this affinity? A broad answer will be encouraged.

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  • $\begingroup$ Hi @Mockingbird360. This question is very very very very very broad and emphasize the amount of "very"s I used. An answer to this question would need an entire dictionary of diastereomers to explain. It's wrong to expect such hard work from an answerer. Limit yourself to asking a particular question at a time. For example, you could point out a specific diastereomer and ask about it's selectivity. I hope you understand. Good luck and post better questions next time! $\endgroup$ – Pritt says Reinstate Monica Jun 6 '17 at 15:39
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    $\begingroup$ In a nutshell, try to shake someone's left hand with your right, and you'll see. $\endgroup$ – Ivan Neretin Jun 6 '17 at 16:02
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Let's set aside compounds for the moment.

Your hands are chiral objects, that is, they are non-superimposable mirror images of each other [see more here]. If you pick up something that is not chiral, like a cup, there is no difference whether you use the left hand or right hand. The "energy" of those two interactions (right hand + cup or left hand + cup) is the same.

Now, let's say you get a pair of gloves made to fit your hands. If you put your left hand into the right-hand glove, it feels different than if you put your left hand into the left-hand glove. You could think of it as those two interactions (left hand + left glove vs left hand + right glove) having different energies.

The reason for this is that enantiomers of chiral objects interact with non-chiral objects with the same energy, but interact with enantiomers of chiral objects with different energy (ignoring coincidental cases, as @Zhe suggests).

The way one enantiomer of a compound "fits" with enantiomers of other compounds (objects) like proteins or chromatography instruments is difficult to predict. Sometimes it is useful to actually model the interactions, but often, like in chromatography, it's enough to know that there should be a difference in energetics of the enantiomers of a compound with a single enantiomer of another chiral object.

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Enantiomeric arrangements (molecules, complexes, etc) have identical energies. However, when you take two enantiomeric objects, their interactions are via diastereomeric arrangements. Barring the very unlikely case of accidental degeneracy, these diastereomeric arrangements have different energies. Different energies of interaction led to different chemical properties, including affinity.

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  • $\begingroup$ Your answer would be better if you add some examples. $\endgroup$ – Partha Sarker Jun 6 '17 at 16:18
  • $\begingroup$ That's true, but "a broad answer will be encouraged." I'm just following directions. Ivan's example of hands is a good one. $\endgroup$ – Zhe Jun 6 '17 at 17:46

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