Optical rotatory dispersion of indoline alkaloids with keto groups

The optical rotatory dispersion curves of a series of indolines, N(a)-acetyl-indolines and N(a)-methoxycarbonyl-indolines containing keto groups have been measured. It has been shown that the absolute stereochemistry of N(a)-acetyl-indolines containing keto groups can still be determined from the character of the Cotton Effect due to the aromatic chromophore, the ketone Cotton Effect however being more difficult to interpret. The use of N(a)-methoxycarbonyl-indoline and indoline chromophores is dangerous due to the complex nature of the Cotton Effect of the former and the overlapping of that of the latter with the ketone Cotton Effect.     

Optical rotatory dispersion of the sparteine alkaloids

Chemistry of Natural Compounds -     

Optical rotatory dispersion of some thalictrum alkaloids

Chemistry of Natural Compounds - For all the bisbenzyltetrahydroisoquinoline alkaloids considered except thalisopine, positive CEs are found in the case of the SS configuration and negative CEs in...     

Optical rotatory dispersion from liquid crystalline solutions and films of hydroxypropylcellulose

The chiroptical properties of (hydroxypropyl)cellulose (HPC) in methanol are measured by optical rotatory dispersion (ORD), both in isotropic solution and in the cholesteric liquid crystalline phase. The ORD spectra of HPC films cast from lyotropic solution are also examined. Isotropic solutions of HPC in methanol provide no ORD evidence for the presence of a helical conformation, or for concentration-induced changes in conformation. The ORD curve of HPC in methanol, when expressed as specific rotation, is independent of polymer concentration for isotropic solutions containing between 1 and 43 per cent polymer by weight. From the slope of Drude plots, the Cotton effect responsible for the observed ORD curve occurs at 175-180 nm. However a 45 per cent liquid crystal-line solution exhibits plain positive dispersion, and the magnitude of the specific rotation is also much greater than that found for solutions containing less than 43 per cent polymer. Results for more concentrated solutions confirm that ORD spectra of lyotropic liquid crystals of HPC in methanol contain a significant positive component that is not accounted for by the de Vries equation for cholesteric reflection. ORD measurements in other solvents and on dry films show that this contribution to the optical activity vanishes when the solvent is removed or when hydrogen bonding is disrupted. The effect is tentatively ascribed to a hydrogen bonded structure that contributes strongly to the optical rotation.     

Optical rotatory dispersion of rare earth crystal

The ORD spectrum of optically active single crystal of praseodymium oxydiacetate has been studied in the visible range at 77 K. The results have been compared with those obtained in the cases of transition metal complexes and other RE complexes with optically active ligands, and correlated with the site symmetry of the RE ion in the crystal. The optical activity has been related to the magnetic dipole strengths of the transitions.     

Optical rotatory dispersion of water-soluble cellulose derivatives

Dilute solutions of water-soluble cellulose esters and also solutions of model compounds — glucose and cellobiose — have been investigated. It has been shown that a definite influence on optical rotatory dispersion is exerted by the conformational difference of the pyranose rings of cellulose arising when the hydroxy groups in the macromolecule are partially replaced by functional groups of different natures.     

Optical rotatory dispersion of 2,3-hexadiene and 2,3-pentadiene

The specific rotation of (P)-2,3-hexadiene (1) was measured as a function of wavelength for the gas phase, the neat liquid, and solutions. There was a surprisingly large difference between the gas phase and condensed phase values. The specific rotation was calculated using B3LYP and CCSD, and the difference in energy between the three low energy conformers was estimated at the G3 level. The Boltzmann-averaged CCSD-calculated rotations using the gauge independent velocity gauge representation, as well as the B3LYP values, are in agreement with the gas-phase experimental values. In order to avoid possible problems associated with the conformers of 1, 2,3-pentadiene (2) also was examined. Here again, there was a large difference between the gas-phase and condensed-phase specific rotations, with the CCSD velocity gauge (and B3LYP) results being close to the gas-phase experimental values. The possibility that 2,3-pentadiene could be distorted on going from the gas to liquid phase, thereby accounting for the effect of phase on the specific rotation, was examined via a Monte Carlo statistical mechanics simulation. No effect on the geometry was found. Specific rotations of 1 found in solutions were similar to those for the liquid phase, indicating that the phase difference was not due to association.     

Optical rotatory dispersion of steroids with various chromophores

Conclusions 1. On the basis of a comparative study of the ORD of steroids containing as chromophores the groups C=O, >C=C–C=C< and C=C, it has been established that in all the compounds the ORD is anomalous in the UV region of the spectrum.2. In steroid compounds the magnitude of the optical rotation increases with an increase in the geometrical dimensions of the chromophoric group.3. The ORD curves of steroid compounds with various -electronic chromophores are highly specific and can be used to study their structure and for identification purposes.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 1, pp. 36–39, 1969     

Optical rotatory dispersion (ORD) of glycogen

The ORD spectra of three types of glycogen in salt solutions at different concentrations, pH and ionic strength values were determined to investigate the influence of these variables on the rotatory power.The ORD curves obtained with the samples recently prepared correspond to positive monotone dispersion curves, similar to available data for the other polysaccharides.Once the mutarotation equilibrium is attained a maximum is observed at 210±10 nm. The rotatory power decreases with the elapsed time and in some cases, it is possible to find a change in the sign of these curves. Such a phenomenon may be attributed to conformational changes in the monomer units constituting the macromolecule.A considerable increase in the rotatory power is found at pH extreme values.The dispersion constant, _c , was calculated by means of a modified Drude equation and results indicate that the _c value is higher for muscle glycogen in the mussel species, suggesting a higher degree of asymmetry in this macromolecule.     

Optical rotatory properties of synthetic polymers. II. Optical rotatory dispersion of poly(propylene sulfide)

Optically active propylene sulfide was polymerized in the presence of potassium hydroxide as catalyst to give optically active poly(propylene sulfide). Rotatory dispersion curves of the polymer thus obtained were measured in benzene and chloroform media. In both cases, the curves were anomalous in shape with the same sign, having troughs at 290 and 275 mμ, respectively. (–)-1,2-Diethylthiopropane was prepared as an optically active model compound of poly(propylene sulfide) in optical rotatory properties. It was found that the model compound also shows anomalous rotatory dispersion both in benzene and chloroform with the same sign. Thus it may be concluded that the anomalous dispersion of poly(propylene sulfide) must be attributed to an additional Cotton effect caused by the absorption of sulfide bonds, which are generally admitted to have absorptions at 200 and 230 mμ (shoulder).