Chapter 14 - Determination of molecular stereochemistry using optical rotatory dispersion, vibrational circular dichroism and vibrational Raman optical activity

Abstract

This chapter describes three chiroptical methods for determining molecular stereochemistry. All three methods represent useful and powerful stereochemical approaches. Instrumentation is inexpensive for optical rotator dispersion (ORD) measurements. Also, ORD is easy to measure and easy to calculate using available quantum mechanical programs. However, to obtain reliable predictions it may be necessary to obtain predictions at the higher levels of theory (such as B3LYP functional and aug-cc-pVDZ basis set). Vibrational circular dichroism (VCD) also became easy to measure with the availability of commercial instrumentation, but the instrumentation is more expensive than that of ORD. Available quantum mechanical programs can be used for routine VCD predictions, but here some background in spectroscopy would be appropriate. Nevertheless, satisfactory VCD predictions can be obtained at a moderate level of theory (such as B3LYP functional and 6-31G* basis set). For vibrational Raman optical activity (VROA), introduction of commercial instrumentation made the measurements easier, but still measurements are a bit more involved than those for ORD or VCD. VROA instrumentation is more expensive than that of either ORD or VCD. Quantum mechanical programs are also available for VROA predictions but VROA calculations are more involved than those of either ORD or VCD. More expertise is needed for ORD or VCD for both, experimental measurements and theoretical calculations. These comments help newcomers to choose one or more of the three methods for their research in molecular stereochemistry.