Stereochemistry for the Study of the Origin of Life

Before exploring up-do-date theories and cutting-edge research activities on the origin of life's molecular asymmetry, this Chap. 2 will provide a brief, comprehensible, and illustrated introduction on common stereochemical terms like chirality, stereogenic center, enantiomer, racemic mixture, optical activity, and homochiral-ity. Stereochemical descriptors like R/S, d/l, (+)/(-), d/l, A/A, and P/M will be explained.

After being familiar with these basic terms, we will focus on techniques often applied in bioanalytical laboratories to gain experimental information on the hand-edness of molecules. Advantages and limitations of chiroptical techniques such as optical rotation dispersion (ORD) including the Cotton effect, and in particular the often used circular dichroism (CD) spectroscopy will be outlined. Briefly, modern vibrational circular dichroism (vCD) techniques and - based on recent advances in the field and nowadays commercially available instruments - the Raman optical activity (ROA) will be introduced.

We will establish the phenomenon that not only molecules and macroscopic structures can be chiral but also electromagnetic waves in form of circularly polarized electromagnetic radiation. We will learn how to characterize "chiral light" with the help of the Stokes parameters I, Q, U, and V . Finally, the chromatographic resolution of enantiomers on chiral stationary phases will be summarized, as their use is common practice in numerous analytical laboratories today. Molecular structures of the most important chiral selectors will be given. Chapter 2 will thus provide a sound basis in order to meet and fully understand the stereochemical vocabulary, the experiments' design, and the measurement strategies, which we will encounter in the upcoming chapters.

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