Racemic mixtures versus achiral compounds

[emitted_echo]

TL;DR

How did we first discover that a racemic mixture had two different chiral compounds when it behaves the same as an achiral compound.

Lately, I've been doing a lot of research on chirality in biochemical and medical contexts; especially from a developmental standpoint. I am aware of how each enantiomer behaves differently from its corresponding mirror-image molecule, but i'm confused by racemic mixtures. I understand on a conceptual level that it's just a mixture between 'right-handed' and 'left-handed' chiralities, but how was this discovered? Everything I have read says that racemic mixtures behave identically to achiral ones since the two essentially cancel out the other's optical properties, so does this mean that there is a chance other compounds we believed to be achiral could simply be racemic mixtures we haven't separated, or is there something I am missing? Additionally, I am aware that it is incredibly complicated to separate them at times- especially depending on what specifically you're working with,- so how were these processes chosen?

Thank you in advance for any responses. I am very new to research on this subject, so any and all help is appreciated.

 

[.Scott]

Whenever you know the molecular structure (ie, the 3D positions of the atoms within the molecule), then you can immediately determine whether it is chiral or achiral - it's just a quick geometry exercise.

Once you determine that it is chiral, and it is either transparent or can be dissolved in a water solution that is transparent, then you can check a sample to see whether it will turn the polarization.

If it does not turn the polarization, then it's either a racemic mixture or its chiral affect on light is minimal.

So, for example, even without a non-racemic fructose sample, you know that the molecules are chiral by their structure. If you test a fructose sample's chiral affect on polarization and find none, you know that either the fructose sample is racemic or the chiral affect on polarization it too subtle to be noticed by your experiment.
In fact, because of its molecular structure, fructose will have a very noticeable affect.

[AI reference removed by the Mentors, since they are not allowed in the technical forums.]