Rotatory Powers Research Articles

Transmittance and reflectance of cholesteric and blue phase liquid crystal

Blue phase liquid crystal display (BPLCD) is emerging as next-generation display, because of its fast response speed and very wide viewing angle. However, it has some weak points to be improved. The light leakage at the dark state affects the contrast ratio, and needs to be analyzed and improved. Considering the double-twist structure of blue phase liquid crystal (BPLC) and the simple twist structure of cholesteric liquid crystal (ChLC), the two twist structures are similar. The transmittances and reflectances of planar and focal conic texture of cholesteric liquid crystal and blue phase II liquid crystal are simulated by finite-difference time domain (FDTD) method. The FDTD method is based on the Maxwell’s equation, and can calculate the optical rotatory power directly. The effective optical rotatory powers of the three liquid crystal states are proposed and compared using the light leakages at the cell with crossed and parallel polarizers. The results show that the transmittance of BPLC with crossed polarizers is lower than that of planar texture and larger than that of focal conic texture of ChLC. The optical rotation of BPLC is not the same at any point in one periodic cross section in the light path because the liquid crystal arrangement is complex, the effective optical rotatory power is defined as the average value of the optical rotatory powers at all points. Comparing with the optical rotatory powers of planar and focal conic textures of ChLC, the optical rotatory power of BPLC is less than that of planar texture and larger than that of focal conic texture. Moreover, the Bragg reflections are also simulated, the results show that blue phase liquid crystal is similar to planar state cholesteric liquid crystal, only the reflection intensity is smaller, and no obvious Bragg reflection appears in focal conic state cholesteric liquid crystal. Considering the optical rotation and Bragg reflection, the light leakage and reflective light of BPLCD cannot be ignored if the helix pitch is not less enough, however, these of focal conic texture of ChLC are very small compared with those of BPLC, as a result, the focal conic texture of ChLC can replace blue phase liquid crystal to obtain the good dark state and high contrast ratio.

Density functional study on chirospectra of hydrogen-bonded systems X− (H2O)3 (X = F, Cl, Br, I)

This paper calculates the molecular structures, infrared, Raman, circular dichroism spectra and optical rotatory powers of some hydrogen-bonded supramolecular systems as a cyclic water trimer, (H2O)3 and its pyramidal halide complexes, X− (H2O)3 (X = F, Cl, Br, I) with the gradient-corrected density functional theory method at the B3LYP/6–311++G(2d,2p) and B3LYP/Aug–cc–pVTZ levels. It finds that the complexation of halide anions with the water trimer can efficiently modulate the chirally optical behaviors. The calculated vibrational circular dichroism spectrum illuminates that the vibrational rotational strength of S(+)–(H2O)3 mostly originates from the O–H rocking modes, whereas chirality of S(–)–X− (H2O)3 (X = F, Cl, Br, I) has its important origin in the O–H stretching modes. The calculated optical rotatory power demonstrates that S(+)–(H2O)3 and S(+)–F−(H2O)3 are positively chiral, whereas S(–)–X−(H2O)3 (X = Cl, Br, I) are negatively chiral. With the polarizable continuum model, calculated bulk solvent effect in the solvents water and carbontetrachloride and argon shows that the positive chirality of S(+)–(H2O)3 is enhanced and the negative chirality of S(–)–X−(H2O)3 (X = Cl, Br, I) and the positive chirality of S(+)–F−(H2O)3 are reduced with an augmentation of the solvent dielectric constant.

Theory and computation of optical rotatory power in inorganic crystals

The classical polarizability theory of optical activity in crystals is elaborated and a method of calculating rotatory power from crystal structure data is described. By varying the polarizabilities of the atoms within reasonable limits, optical rotatory powers are computed for crystals of α-quartz, AlPO4, cinnabar, Bi12SiO20, Bi12GeO20, α-LiIO3, NaClO3 and NaBrO3. In general, the agreement between theory and experiment is excellent. As expected, considerable variability in polarizabilities is required in different structures in order to obtain satisfactory fits to the observed refractive indices and rotatory powers. The orientations of anisotropic polarizability ellipsoids derived in the course of the calculation are compared with those suggested earlier by Glazer & Stadnicka [J. Appl. Cryst. (1986), 19, 108-122].

Spherulite morphology in liquid crystals of polybenzylglutamates. Optical rotatory power and effect of magnetic field

AbstractThe stepwise growth and emergence of spherulitic structures as isolated entities from lyotropic solutions of polybenzylglutamate liquid crystals is described. Spherulites that form ringed internal structures indicative of a cholesteric organization of macromolecules have large optical rotatory powers. The sense of the rotation is solvent dependent. The morphology of the spherulite is distorted in the presence of a magnetic field. The pitch of the cumulative twist of “onion‐shell” molecular layers was measured as a function of field strength and found to follow the theoretical form shown previously to hold for continuous‐phase polypeptide liquid crystals.

Optically active α- and β-naphthalene derivatives—IV : Synthesis and optical purity of 2-methyl-3- and 2,2-dimethyl-3- (α- and β-naphthyl)-butanes

The ( S) methyl 3-(α- and β-naphthyl)-butanoates have been related to the optically active title compounds and to 2-(α- and β-naphthyl)-butanoic-, -3-methylbutanoic- and -3,3-dimethylbutanoic acids. The absolute configurations and maximum rotatory powers (this is in fact, all that has been measured, in terms of rotatory power) of the naphthyl hydrocarbons and their related compounds have been established.

Ion‐dipole interactions and chiroptical property changes of an optically active nylon‐type polyamide in CaCl2‐methanol solutions

AbstractThe chiroptical properties of poly(‐) 1,2‐diaminopropane sebacamide) (I) and of its model molecule: the N, N'‐didecanoyl (‐) 1,2‐diaminopropane (II) in CaCl2‐methanol solutions have been investigated by ORD (optical rotatory dispersion) and CD (circular dichroism) over a wide range of salt/monomeric units or salt/model molar ratios τ. The origin of the observed CD bands is discussed on the basis of the electronic transitions of isolated amide chromophores. The polymer behaves exactly as if the monomeric units were completely independent. The optical activities of (I) and (II) in CaCl2‐methanol solutions are found to depend on two overlapping phenomena: an ion‐dipole complex which prevails at low τ; a solvent‐like effect of the excess salt on the complexed species. A method for calculating the ion‐dipole association constant Kc from the optical rotatory power changes as a function of τ, is described. It is not necessary to know [ϕms] and [mms], the molar specific rotatory powers of the model and polymeric complexed species, which are subsequently deduced using Kc. The structure of the ion‐dipole complex and the nature of the solvent‐like effect are discussed.

Oligourethan dimers having asymmetric carbon atoms in the main chain. Oligourethans. V1

AbstractA series of oligourethan dimers having asymmetric carbon atoms in the main chain was prepared by the reaction between 1‐alkyl‐2‐acetoxyethyl isocyanates and methyl l‐alkyl‐2‐hydroxyethylcarbamates; their melting points, rotatory powers and RF‐values were determined. The dimers prepared are represented by a general formula, magnified image where R and R' are H, methyl (L and DL‐forms), i‐propyl (L and DL), i‐butyl (L and DL) or benzyl (L) groups. Certain relationships have been found between the structure and rotatory power resp. RF‐value.

Faraday Rotations of Divalent Rare-Earth Ions in Fluorides. III

A large rotatory power for ${\mathrm{Eu}}^{2+}$ in cubic fluoride lattices has been observed in the visible range. At frequencies sufficiently removed from the absorption bands, the rotation is proportional to the magnetization. This suggests that the upper levels in the allowed optical transitions are of the ${P}_{J}$ character. Measurements on Ca${\mathrm{F}}_{2}$ and Sr${\mathrm{F}}_{2}$ crystals doped with very low concentrations of Eu (\ensuremath{\sim}0.005%) also suggest some possible structure for the strong, sharp characteristic line of ${\mathrm{Eu}}^{2+}$ near 4000 \AA{}. The rotatory powers of several other divalent rare-earth ions in fluorides have also been measured.

Optically Active Amines. I. N-Isopropylidene Derivatives of Optically Active Open Chain Primary Amines and Their Rotatory Powers

<b>Optically Active Amines. I. N-Isopropylidene Derivatives of Optically Active Open Chain Primary Amines and Their Rotatory Powers</b>

Optical Rotatory Powers of Alkaloids

Tables of Constants and Numerical Data 11: Selected Constants: Optical Rotatory Power. 4: Alkaloids. By Prof. J.-P. Mathieu and Prof. M.-M. Janot. (Publication subsidized by the Member Countries of the International Commission of Tables of Constants and by the Centre National de la Recherche Scientifique.) Pp. v + 211. (London and New York: Pergamon Press, 1959.) 160s. net.

Vicinal Action in Steroids

THE optical rotatory powers of steroidal compounds can be correlated by means of the method of molecular rotation differences, and such correlation has been shown to be of value in solving certain types of structural problem1. In some cases anomalies of optical rotatory power occur which cannot be ascribed to trivial causes, but which must be due to disturbing factors generally given the name 'vicinal action'.

The Effect of the Rotation of Groups about Bonds on Optical Rotatory Power

It is shown that the numerical value of the optical activity of an optically active compound is markedly reduced if the groups surrounding the asymmetric atoms in the compound possess a threefold axial symmetry about the bonds connecting them with the asymmetric atoms. This threefold symmetry may be either inherent in the groups themselves, or it may be acquired by them through the free rotation of the groups about these bonds or by their orienting themselves to equal extents in each of the three possible equilibrium positions about each bond. The order of magnitude of the numerical value of the optical activity is thus a measure of the freedom of orientation about single bonds of the groups in an asymmetric molecule. That this effect is actually a dominant factor in determining the order of magnitude of the optical activity is proved by the contrast in the optical activities of cyclic and open chain compounds. It is shown to have an important effect on the temperature coefficient of optical activity and to lie at the root of the observed differences in the orders of magnitude of the rotatory powers of liquids and crystalline solids. The structures of certain sulphur compounds, polypeptides, and proteins are discussed in the light of the magnitudes of their optical activities.

The Rotatory Powers of Substituted Camphoranilic Acids.

The Rotatory Powers of Substituted Camphoranilic Acids.

Rotatory Powers of Some Disubstituted , Camphoranilic Acids.

Rotatory Powers of Some Disubstituted , Camphoranilic Acids.

Studies in Optical Rotation. Rotatory Powers of Acidyl-biscamphorquinonehydrazones and Camphorylthiocarbamylhydrazides and Attempts to Prepare Compounds Possessing Abnormal Rotation.

Studies in Optical Rotation. Rotatory Powers of Acidyl-biscamphorquinonehydrazones and Camphorylthiocarbamylhydrazides and Attempts to Prepare Compounds Possessing Abnormal Rotation.

Rotatory power and chemical constitution

The following acids have been prepared and resolved:a-benzyl,p-brombenzyl,m-brombenzyl,p-carboxybenzyl,m-carboxybenzyl-n-caproic acids. The molecular rotatory powers have been measured in order to see whether any alternating effect on rotatory power could be detected. It is possible that such an effect exists but the results obtained we only put forward tentatively.

Rotatory Powers of some Substituted Camphoranilic Acids and Camphorophenyl Imides.

Rotatory Powers of some Substituted Camphoranilic Acids and Camphorophenyl Imides.

Optical rotatory power of vapours. part I.— Rotatory dispersion of camphor and of camphorquinone, especially in the region of absorption

The discovery of optical rotation in vapours was made in 1818 by Biot, who detected the existence of optical rotatory power and of a normal type of rotatory dispersion in a 30-metre column of turpentine-vapour prior to the conflagration which destroyed his apparatus. A quantitative study of the specific rotatory powers of liquids and vapours was made in 1864 by Gernez, who compared the rotations produced by 4-metres of the vapours of the essential oils of orange, Seville orange, and turpentine with those produced in the liquids. These rotations were substantially equal in the case of turpentine, where the specific rotatory power of the liquid was almost independent of temperature, although a small progressive decrease was observed both on heating and on vaporisation. In the other two cases, however, a rapid decrease of specific rotatory power with rise of temperature in the liquid was followed by a slighly more rapid decrease on passing from liquid to vapour, so that the specific rotatory powers in the vapour were definitely smaller than in the liquid state. During the half century which has elapsed since Gernez worked on the subject, no further measurements appear to have been made of the rotatory powers of vapours. It is obvious, however, that the difficulty of predicting optical rotations would be substantially reduced if the disturbing influence of contiguous molecules could be eliminated by observing the rotations in a dilute vapour instead of in solution, and that progress in the theoretical study of this problem may therefore depend fundamentally on experimental work of this kind. The primary object of the experiments now described was therefore to develop a method for measuring the optical rotatory powers of vapours, and to apply it to the typical cases of camphor and of camphorquinone. The principal interest of the work, however, depends on the fact that observations of rotatory dispersion were made in the region of absorption, covered by the well-known ketonic and quinonoid bands, as well as in the range of wavelengths within which these compounds are completely transparent. The combination of these two lines of investigation is indeed a perfectly logical procedure, since the extreme dilution, which is often required in order to penetrate the region of absorption, is provided very readily by a vapour, the concentration of which is already limited by its vapour-pressure, and can be reduced to an indefinite extent by further reductions of pressure.

The optical rotatory power of quartz on either side of an infra-red absorption band

Drude’s equation for natural optical rotations depends on the existence of “ions” of characteristic frequency, of which each type contributes a partial rotation to the total rotatory power of the medium. There is nothing in the equation to limit the range of these frequencies, but in discussing the rotatory power of quartz (the only substance for which sufficient data were then avail­able), Drude himself concluded that “the kinds of ions whose natural periods lie in the infra-red are inactive” (‘Physical Optics,’ 1907, translation, p. 413). An alternative view was put forward by R. W. Wood, who concluded that a "spurious” anomaly could be produced in colourless media by the combined influence of an infra-red and an ultra-violet absorption band (‘Physical Optics,’ 1919 edition, p. 492); and C. E. Wood and Nicholas have applied the same theory in the hope of deducing the configuration of the molecule from the sign of an infra-red term of which the existence is not yet established by experiment. Experiments on these lines have, however, already been made by Ingersol, who found that the rotatory powers of a series of typical compounds decreased progressively in the infra-red region, right up to the limit of transparency of the medium. This experimental result is in agreement with the conclusions of Kuhn (private communication, of ‘Z. Phys. Chem.,’ B, vol. 4, p. 14 (1929), who anticipates that all rotations will diminish asympto­tically to zero in the infra-red; but it is directly opposed to the theoretical deductions of the authors cited above, whose diagrams represent the rotations as increasing asymptotically to ± ∞ on approaching a characteristic frequency in the infra-red. Moreover, since the rotatory powers of linonene and pinene decrease progressively, even when passing through a region which includes three absorption bands, it is clear that the phenomenon discovered by Cotton in coloured organic compounds is not reproduced in these infra-red bands.

CCCLII.—The structure of carbohydrates and their optical rotatory power. Part V. The optical rotatory powers of methylated lactones derived from the simple sugars

CCCLII.—The structure of carbohydrates and their optical rotatory power. Part V. The optical rotatory powers of methylated lactones derived from the simple sugars