Chiral NMR?

  • #1
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Main Question or Discussion Point

Is it possible these days to directly determine the chirality of your molecule without the need of a chiral auxiliary?

http://www.sciencedirect.com/science/article/pii/S0301010405004970

This would be extremely useful if this technology ever came to fruition. Can anyone explain how this works to a non-physical chemist?
 

Answers and Replies

  • #2
DrDu
Science Advisor
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Is it possible these days to directly determine the chirality of your molecule without the need of a chiral auxiliary?

http://www.sciencedirect.com/science/article/pii/S0301010405004970

This would be extremely useful if this technology ever came to fruition. Can anyone explain how this works to a non-physical chemist?
Non-chiral systems are inversion symmetric. A magnetic dipole moment vector is transformed into itself on inversion (consider the motion of an electron on a circular orbit and what happens when you chance x->-x and y->-y) while an electric dipole moment changes direction (positive and negative charges are swapped). Hence magnetic and electric moments are not coupled. While the magnetic field in NMR may induce magnetic polarization, it can't induce electric polarization.
In a chiral substance this is different. A magnetic polarization may be accompanied by an electric one and they may either constructively or destructively interfere in absorption or emission of radio frequency. This not only holds in NMR spectroscopy but also e.g. in IR spectroscopy where determination of absolute configuration has already been proven.
 

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