Specific rotation Spectrum, visible absorption

The rotatory dispersion of amino acids in the visible range of the spectrum has been studied by several workers (Karrer and Kaase, 1919 Waser, 1923 Pertzoff, 1927). Recently, Patterson and Erode (1943) have published detailed results with thirteen a-amino acids. With most compounds studied, the dispersion is normal, i.e., the specific rotation [a] at a particular wave length can be expressed by a one-term Drude equation which has the form a = a/(X — Xo ), where a and Xo are constants. It is likely that, if measurements were extended to the far ultraviolet, amino acids, like many other optically active compounds, would exhibit anomalous dispersion, especially in those parts of the spectrum in which absorption of amino and carboxyl groups becomes significant. It appears, especially from the work of Patterson and Erode (1943) that the l forms of amino acids fall into three classes Group I consists of those amino acids which have a normal and positive dispersion for this class, to which most purely aliphatic amino acids belong, Xo has... 

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