Optical rotation dispersion spectra

The units for the specific rotation are deg-cm /decagram. The light path b is expressed in decimeters and the concentration C is expressed in grams/100 cm . If the specific rotation is multiplied by molecular weight M and divided by 100, it gives rise to molar rotation whose units are deg-cm /decimole. Note that the units for [Ml and [0) are identical. Elxperimental determination of [M ] at different wavelengths would give rise to optical rotatory dispersion spectrum. 

The optical rotation dispersion and circular dichroism are caused by the same phenomenon—namely, the different interaction of left- and right-handed light with an optically active species hence, it is not surprising that a strict relationship exists between ORD and CD spectra of the same compound. In fact, the ORD spectrum can be obtained from the CD spectrum, and vice versa, by using the so-called Kramers-Kronig transformations. Usually the ORD spectrum is recorded in... 

The dielectric constant is a natural choice of order parameter to study freezing of dipolar liquids, because of the large change in the orientational polarizability between the liquid and solid phases. The dielectric relaxation time was calculated by fitting the dispersion spectrum of the complex permittivity near resonance to the Debye model of orientational relaxation. In the Debye dispersion relation (equation (3)), ij is the frequency of the applied potential and t is the orientational (rotational) relaxation time of a dipolar molecule. The subscript s refers to static permittivity (low frequency limit, when the dipoles have sufficient time to be in phase with the applied field). The subscript oo refers to the optical permittivity (high frequency limit) and is a measure of the induced component of the permittivity. 

Optical rotary dispersion (ORD) is the measurement of the optical rotation as a hinction of the wavelength. The ORD spectrum of c/s-[Co(en)2Cl2] is shown in Fig. 5.5(a). Wavelength A (644 nm) is the red Cd line used by Werner in his measurements which gives a (-) rotation for the complex. The wavelength B (589 nm) is the sodium D line and gives a (+) rotation. Clearly it is necessary to specify the wavelength at which the optical rotation is measured. 

The extraordinary quality of the experiment at Oxford can be seen in Fig. 10.4 which shows the optical rotation spectrum for the 8757 A line in atomic bismuth. The dispersion shaped profiles are centred on the positions of the hyperfine components (indicated by arrows). The curve shows the theoretical expectations in the SM and is in amazing agreement with the data. Note that the spectrum would be flat and featureless without the parity violation. (For the latest data see Macpherson et al., 1991.)... 

The most common form of optical activity was first measured at a constant wavelength by the angle of rotation of linearly polarized light. More recently the measurements have been extended to the entire range of visible and attainable ultraviolet regions where electronic transitions are observed, giving rise to the ORD technique (Optical Rotatory Dispersion). The Cotton effects appear in the region of optically active absorption bands outside of these bands the plain curve spectrum is also dependent on all the electronic transitions of the chromophores. 

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