Temperature Dependence Of Optical Activity Research Articles

Optical rotatory power of quartz between 77 K and 325 K for 1030 nm wavelength

We report on the experimental characterisation of the temperature dependence of the optical rotatory power of crystalline right-handed $\alpha$α-quartz at 1030 nm wavelength. The temperature range covered in this study is between 77 K and 325 K. For the measurement we propagated light through a 13.11 mm thick quartz plate collinearly with the optic axis. The plate is anti-reflection coated and rotates the polarisation plane of 1030 nm light by 89.3 deg at room temperature, corresponding to a specific rotatory power of 6.8 deg/mm. When placed between parallel polarisers, the transmission through the system was 0.03% at room temperature and increased to 1% at 77 K, showing a measurable change in rotatory power. At 77 K, the angle of rotation imparted by the quartz plate is 85 deg, corresponding to a specific rotatory power of 6.5 deg/mm. To the best of our knowledge, this is the first time that the temperature dependence of optical activity of $\alpha$α-quartz is reported for cryogenic temperatures in the infrared. We expect that the measurement results provided in this paper will assist in the design and characterisation of optical systems operating under cryogenic conditions.

Temperature dependence of optical activity of sugar solutions

The temperature dependence of optical activity of solutions of metabolic sugars is investigated and the activation energy of the reaction of association into supramolecular structures is determined. On the basis of the values of the activation energy and with consideration of the effect of time and place and orientation of the instrument on the optical activity of sugars, a suggestion is expressed concerning their key role in the mechanism of adaptation of living systems to environmental changes.

Temperature dependence of optical activity and circular dichroism in α‐ZnP2 crystals

AbstractThe circular birefringence related to the gyration components along and perpendicular to the optical axis and the circular dichroism of tetragonal α‐ZnP2 single crystals are determined in the temperature range 290–450 K, using universal null‐polarimetric techniques. The oscillatory temperature behaviour of the optical rotatory power and the ellipticity of light passed through the crystal in the (001) direction is quantitatively well explained by the influence of multiple reflections of light. The observed thermal hysteresis and dependence of the gyration on sample prehistory testify indirectly the availability of incommensurately modulated structure in α‐ZnP2.

Reinvestigation of optical activity in the course of the ferroelastic phase transition in cadmium-langbeinite, K2Cd2(SO4)3

Abstract The three tensor components of optical activity in orthorhombic K2Cd2(SO4)3 were determined at 298 K, 417 K and 443 K. The room-temperature values of the rotatory power ° mm−1) along [100], [010], and [001] are -2.7(9), -1.8(2), 2.9(5). The temperature dependence of optical activity along the optical axes was measured and is in accord for 300 K and in the cubic phase with previous investigations. The thermal evolution of the optical activity reveals a steep step at the phase transition temperature of 432 K. The calculation of optical activity and refractivity, employing a dipole-dipole model, is close to the experiment. The sign of the chirality of the samples is not affected by the transition. The value of the trace of the tensor components remains close to the cubic-phase value and is compatible with the symmetry breaking which is responsible for the observed anisotropy of the optical activity in the orthorhombic phase.

Poly‐(+)‐2‐methylbutyl acrylate. Preparation, IR and NMR spectra, optical rotatory dispersion and ultraviolet spectra

AbstractIR, NMR, ORD, and UV measurements were carried out on the poly‐(+)‐2‐methylbutyl acrylates obtained by the radical (R‐PMBA) and anionic (A‐PMBA) polymerization processes and on the (+)‐2‐methylbutyl isobutyrate (model compound).There are not any differences in IR and NMR spectra of R‐ and A‐PMBA. The values of molar rotation decrease in the order of R‐PMBA, A‐PMBA, and the model compound, while the values of the extinction coefficient decrease in the order of A‐PMBA, R‐PMBA, and the model compound.Temperature coefficients of the molar rotation of PMBA polymers and the model compound are of the order of 10−3 between 30 and 60°C, but the temperature dependence of the extinction coefficients is very small.The observed temperature dependence of optical activity arise mainly from the conformational variations of side chains though very local conformational contributions of the main chain would exist.The absorption peak of the model compound shifts to the shorter wave length region when the polarity of the solvent used is larger.

Optical rotatory dispersion studies of poly(l‐α‐methylbenzyl methacrylate) and poly(menthyl methacrylate) in solution

AbstractOptical rotatory dispersion studies were carried out on solutions of poly(l‐α‐methylbenzyl methacrylate) and poly (l‐menthyl methacrylate) samples of varying tacticity. Monomeric analogues α‐methylbenzyl pivalate and menthyl pivalate were also investigated in the same way. Ultraviolet spectra of the α‐methylbenzyl series were obtained.The general shape and form of the optical rotation spectra were similar for the several α‐methylbenzyl polymer samples and monomer analogue. The isotactic polymer showed generally higher optical activity than both the syndiotactic and atactic polymers and the monomeric analogue. This was found to be true in several solvent systems. The ratio of the optical activity of the polymer to that of the monomer increased uniformly with decreasing wave length. The temperature dependence of optical activity was small. The ultraviolet spectra of polymeric and monomeric species were very much the same down to the lowest wave lengths measured, of the order of 210 mμ.The menthyl polymers and monomer analogue also showed optical rotation spectra which were similar to each other. For this material all polymers had higher optical activity than the monomeric analogue, but in contrast to that which was found for the α‐methylbenzyl systems, the syndiotactic and atactic polymers showed higher optical rotation than the isotactic material.The relationship of the optical activity of the polymers in solution to the specific conformational structure present is obscured partly by solvent interaction and partly by the fact that the effects of polymer structure on optical activity are small since the asymmetric carbon or carbon atoms are connected by several intermediate bonds to the skeletal backbone of the molecule. The importance of the excited states of the important chromophoric groups of the polymer molecule on the optical activity is discussed.