Of the 61M known compounds, it is estimated only around 1M have been reported as scalemic, a term used to describe any non-racemic chiral compound. Of these, an unknown proportion have a clearly established absolute configuration for the dominant enantiomer. Absolute configurations can be established by anomalous dispersion X-ray crystallography (and it is estimated about 11,000 such determinations have been made) or chiroptical spectroscopies. This talk concentrates on the latter, and in particular illustrates how electronic circular dichroism, optical rotatory power, optical rotatory dispersion and vibrational circular dichroism, coupled with powerful modern quantum mechanical simulations, can be used to assign the absolute configurations of scalemic molecules. In effect, the QM "chiroptical instrument" is seen as an indespensible symbiotic component of a modern synthetic laboratory, and the skills needed to operate it properly should be part of the training of any aspiring synthetic chemist who may be making scalemic molecules.

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