Net atomic charges, electric moments, and sign and magnitude of optical rotatory power in α-TeO2 at 296 K

2020 ◽  
Vol 53 (5) ◽  
pp. 1252-1256
Author(s):  
M. Karppinen
Keyword(s):  
Principal Axis ◽  
Optical Rotation ◽  
Rotatory Power ◽  
Atomic Charges ◽  
Optical Rotatory ◽  
Point Charge Model ◽  
Positive Direction ◽  
Optical Refraction ◽  
Charge Model ◽  
Optical Rotatory Power

Optical activity is determined from a point charge model in one enantiomorph of a chiral and semiconducting α-TeO2 crystal. Net atomic charges of Te and O atoms are iterated and electric moments derived. Second electric moments in the principal axis directions are calculated and their ratio is fitted by comparison with the corresponding ratio of the optical refraction indices. The components of the axial vectors are calculated and converted to the gyration tensor components. The optical rotatory power in the positive direction of the optic axis is determined, and the sense of optical rotation is defined from transformations of polar vectors of first rank of the TeO2 groups and visually confirmed in both enantiomorphs.

scholarly journals Optical rotatory power. I—A theoretical calculation for a molecule containing only isotropic refractive centres

1934 ◽  
Vol 144 (853) ◽  
pp. 655-675 ◽  
Keyword(s):  
Theoretical Calculation ◽  
Optical Activity ◽  
Chemical Structure ◽  
Central Atom ◽  
Optical Rotation ◽  
Rotatory Power ◽  
Theoretical Formula ◽  
Optical Rotatory ◽  
Present Communication ◽  
Optical Rotatory Power

Ever since the time of van’t Hoff and Le Bel the number investigations dependent on optical activity, or attempting to elucidate optical activity, has been very great, and it is remarkable that, even at the present time, there is no theoretical formula which gives the relation between the magnitude of the rotation and the chemical structure of the molecule concerned. The present communication supplies this want with regard to the molecule of the simplest asymmetric type: the molecule with four different groups attached to one central atom. Various special hypothese have been postulated to explain optical activity, but a few investigators have shown quite definitely that there is no necessity for any of these hypotheses. Born* and Oseen have shown independently that, if the molecule has a dissymmetric structure, the ordinary refractive properties of the atoms will account for an optical rotation. Gray* and de Mallemann have attempted calculations of formulæ for optical retatory power on this basis. However, it has not been possible to condense the numerous algebraic terms which occur in these calculaations into a compact form.

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

1932 ◽  
Vol 135 (826) ◽  
pp. 13-22 ◽  
Keyword(s):  
Optical Rotation ◽  
Rotatory Power ◽  
Rapid Decrease ◽  
Rotatory Dispersion ◽  
Optical Rotatory ◽  
Primary Object ◽  
The Subject ◽  
Optical Rotations ◽  
Optical Rotatory Power ◽  
Made In

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.

Polarimetric and nuclear magnetic resonance studies of the complexation of mercury by thiols

1988 ◽  
Vol 66 (12) ◽  
pp. 3184-3189 ◽  
Author(s):  
Mohamed M. Shoukry ◽  
Bruce V. Cheesman ◽  
Dallas L. Rabenstein
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Formation Constant ◽  
Ph Dependence ◽  
Equilibrium Constants ◽  
Rotatory Power ◽  
Acid Dissociation ◽  
Optical Rotatory ◽  
Optical Rotatory Power ◽  
Nuclear Magnetic

The complexation of Hg(II) by glutathione has been studied by polarimetry under conditions of excess ligand with the objective of characterizing formation of the 3:1 complex, Hg(glutathione)3. The optical rotatory power of solutions containing glutathione only and of solutions containing glutathione and Hg(II) at ratios of 2:1, 2.5:1, 3:1, and 4:1 was measured as a function of pH. Acid dissociation constants for the ammonium and thiol groups of glutathione and for the two ammonium groups of Hg(glutathione)2 and the formation constant of the 3:1 complex (Hg(glutathione)2 + glutathione [Formula: see text] Hg(glutathione)3) were determined from the pH dependence of the optical rotatory power. The value obtained for the formation constant, Kf = 1.5 × 103, indicates that binding of the third ligand to form Hg(glutathione)3 is much weaker than binding of the first two glutathione ligands. However, calculations indicate that binding is sufficiently strong that a significant fraction of Hg(II) is present as Hg(glutathione)3 under physiological conditions. Equilibrium constants were also determined by polarimetry and by 13C nuclear magnetic resonance for the displacement of one thiolate ligand by another (RSHgSR + R′SH [Formula: see text] RSHgSR′ + RSH; RSHgSR′ + R′SH [Formula: see text] R′SHgSR′ + RSH). The results indicate that, at pH 5.5 and at physiological pH, the relative stability increases in the order Hg(glutathione)2 < Hg(penicillamine)2 < Hg(mercaptoethylamine) 2. However, when competitive protonation of free ligand is accounted for, it is shown that the intrinsic stability of the complexes increases in the order Hg(penicillamine)2 < Hg(mercaptoethylamine)2 < Hg(glutathione)2, which parallels the order of the Brønsted basicity of the thiolate ligands.

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