Kerr constants

T471), 959 <55ACS847> molar Kerr constant, 3, 947 (65JCS571)... 

Dipole moments and molar Kerr constants of phenotellurazines were measured (85ZOB846). The results suggest a significant shift of electron density from the benzene rings toward the heterocycle. 

The Kerr effect is the birefringence induced in a medium by an external electric field (12). From such an experiment we deduce the molar Kerr constant mK, thus... 

In table I we present the molar Kerr constants and mean square dipole moments of three fluorinated polymers, poly (trifluoroethylene) (PFjE), polylvinylidene fluoride) (PVF2) and poly(fluoromethylene) (PFM), dissolved in p-dioxane. The results show the sensitivity of mK to the degree and type of fluorination varying over an order of magnitude and also changing sign. Calculations of mK and for comparison are in progress (5). 

Figure 1. Molar kerr constant values (x 10 ucm7SC 2mot ) calculatedforpolyfstyrene-co-p-bromostyrene) copolymers as a function of composition Cand tact icily pr Black squares are experimental results. (Reproduced from Ref 3. Copyright 1981, American...

Steady-state birefringence. The investigation of the steady-state birefringence variation versus the squared electric field leads to the knowledge of the Kerr constant the electrical parameters... 

The values of permanent dipole moment y, optical anisotropy gl g Kerr constant k are reported in Table I. We note that the kgp and - g values increase at 25 C as the starting concentration of the solution increases.Increasing temperature from 25°C to 60°C for the, 6 % solution results in lowering these two pa-... 

Dipole moment studies and molar Kerr constants, in C6Hi2 at 25 °C, have proved of much use in adducing the conformations of acylpyridines (73JCS(P2)l46l)..4-Formylpyridine is planar, but the acetyl group appears to be twisted about 25° from the plane of the pyridine ring in 4-acetylpyridine. The conformation of 4-benzoylpyridine must be defined by two angles 6 and 4> as in (262). The preferred conformation is calculated to be 6 = = 25°, consistent with the result for 4-acetylpyridine. 

Measurements of dipole moments, Kerr constants, and dielectric absorption have been employed (81RCR336) widely to obtain information on the conformational equilibrium in acyl heterocycles. Details on conformer structures and populations depend on the choice of additive scheme, group moments, or polarizability tensor in the case of Kerr constants. Several early conclusions, especially for furan- and thiophene-2-carboxaldehyde, appeared contradictory, owing to the choice of these quantities. A more precise definition of polarizability tensors for several heterocycles and a choice of group moments and additive schemes tested on a large amount of available experimental results and supported by accurate theoretical calculations have led to more confidence in the use of experimental dipole moments and Kerr constants in conformational analysis. A limitation of the method is that the... 

DM, Dipole moments KC, Kerr constants LIS, lanthanide-induced shifts. 

The results of dipole moment and Kerr constant elaboration indicated (84JST(116)377) that in the 2-pivaloyl derivatives of furan and pyrrole the... 

In a-pyridyl (32), Kerr constants (66JCS(B)420) support a structure, confirmed by X-ray analysis, with a dihedral angle of 80-83° between the two C=0 planes, and each fragment adopting an N,0-trans orientation. 

C-NMR, dipole moments, Kerr constants, and IR and UV spectroscopy have been employed. The assignment of NMR signals to the separate con-formers seems (78JCS(P2)99) to cause the misleading results obtained when C chemical shifts alone are used in conformational analysis of -acylazoles and N-acylindole. 

Based on comparison of calculation and experiment for the molar Kerr constants mK and the dipole moments squared of the a,o>-dibromoalkanes lx S 17) in cyclohexane. 

Molar Kerr constants mK and dipole moments squared of polytoxyethylene giycoils (POEG) and polyjoxyethylene dimethyl ether)s (POEDE) are reported in the isotropically polarizable solvents carbon tetrachloride, cyclohexane, and dioxane. Data for mK/x for POEG appear to reach an asymptotical value, Calculations of mK/x and /x based on the RIS model show good agreement with the experimental results. 

Two different RIS models are used to calculate dipole moments and molar Kerr constants for PVB oligomers. The obtained results are compared with experimental results. 

The optical anisotropies y and molar Kerr constants mK of model compounds, and of polylp-chlorostyrene) and polyfp-bromostyrene), are determined. Averages and over all conformations of the polymer chains are calculated as functions of the fraction wm of the meso diads using the RIS model originally developed for PS. 

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