[agugliotta]

In regard to infrared and isomers (enantiomers in particular), can FTIR distinguish these molecules?  For example, if an IR absorbance spectrum for an unidentified drugs hits on l-amphetamine hydrochloride, does this mean that is a definitive id of the unknown drug? or could the unknown be d-amptheramine hydrochloride also?  .. what about cocaine enantiomers? Thank you!

I know IR is designed to give structural information, but I wasn't sure about isomers. Thanks.

[Doc Oc]

Enantiomers have the same physical traits so they are not distinguishable by IR.

[Babcock_Hall]

I agree with Doc Oc, but I will point out one possible exception.  Enantiomers are not distinguishable, unless they are in a chiral environment.  I would predict that if you dissolved each enantiomer in in S-2-butanol (for example) they might be distinguishable, but I don't know how practical such an experiment would be.

[Corribus]

You can also use FTIR/VCD to distinguish between enantiomers.

See Ito et al, JACS 1979 101, 2, 496-498. http://pubs.acs.org/doi/abs/10.1021/ja00496a045

A general description of VCD can be found here.

https://en.wikipedia.org/wiki/Vibrational_circular_dichroism

[agugliotta]

Thank you all!  So ultimately, with using FTIR, you wouldn't know which stereoisomer is present (i.e. l or d-amphetamine) as it could really be either one.

Thank you again.