Dipole measurement

Dipol-kraft,/. dipole force, -messung,/. dipole measurement, -strahlung, /. dipole radiation. 

This distinction is meaningful if the resultant distribution function is of the type shown in Figure 4.7 (Szwarc, 1965). This figure shows that there is a high probability that the cation and anion are either in contact, separated by a solvent molecule or far apart (Szwarc, 1965). Intermediate positions are improbable. The structure of solvated ion-pairs has been studied by Grunwald (1979) using dipole measurements. 

Ti(R2rftc)2Cl2 complexes are, in view of the spectral data, the conductance studies and the dipole measurements in benzene, six-coordinated cis compounds (9). 

In Equation 12.6 p, is the permanent dipole moment, h is Planck s constant, I the moment of inertia, j the angular momentum quantum number, and M and K the projection of the angular momentum on the electric field vector or axis of symmetry of the molecule, respectively. Obviously if the electric field strength is known, and the j state is reliably identified (this can be done using the Stark shift itself) it is possible to determine the dipole moment precisely. The high sensitivity of the method enables one to measure differences in dipole moments between isotopes and/or between ground and excited vibrational states (and in favorable cases dipole differences between rotational states). Dipole measurements precise to 0.001 D, or better, for moments in the range 0.5-2D are typical (Table 12.1). 

The conception of the electrostatic bond has been found to be most valuable in the field of inorganic chemistry and has helped to clarify a great many phenomena. It has frequently made it possible to predict properties both of unknown compounds and of those which have been little investigated. Nevertheless, a number of difficulties have been encountered. For example, in Section 43, it was shown that the theory did not really provide a satisfactory explanation of the low symmetry of molecules. Again, the theory failed to explain the volatility and small dipole moment of the compounds CO, NO, C120, etc., and lastly, it threw no light whatever on the reason for the existence of molecules of elements such as H2, Cl2, Oa, N2, etc., especially as dipole measurements show that the formulae H+H, Ci+ci are excluded. 

Dipole measurements of PEMA are performed in different solvents, and experimental measurements are theoretically analyzed on the basis of the RIS formalism. Energetic and geometric parameters proposed for PMMA are found to give a reasonable account of the experimentally measured values, in general. However, the change in average dipoles with temperature is found to exhibit a substantial dependence on the type of solvent, which indicates the importance of specific solvent-polymer interaction on the conformational characteristics of the chain. 

The interpretation of physical data on an adsorption bond is generally far more complicated than for an ordinary chemical bond. This holds to some extent for spectroscopic measurements [see, for instance, results of infrared absorption by Eischens (18) and co-workers], but to a far greater extent for magnetic properties and dipole measurements. 

The optically active derivative I was founded in a mixture of d-, 1- and meso-forms. The cis-trans isomers of II could be separated by careful fractional distillation or by gas chromatography. The configuration of the chlorophenyl derivatives could be estimated by dipole measurements. The chlorine atoms were exchanged with hydrogen by Grignard reaction and hydrolysis, so the configuration of the phenyl compounds was also determined. The cis and trans forms differ in their physicochemical constants and in their NMR spectra. 

Thiadiazole has a dipole moment of 3.0 D directed from the S atom toward the center of the N—N bond, as calculated by a combination of techniques (68AHC(9)165, p. 200). Dipole measurements have been utilized to substantiate the mesoionic structure of certain... 

By comparing the dipole moments of 1,2,3-triazole with its two 1-methyl-lff (23) and 2-methyl-2H derivatives (24) in benzene at 25 °C, it was found that 83% of 1,2,3-triazole existed as the symmetrical 2H-form (2). From a second measurement at 45 °C the thermodynamic parameters of the equilibrium were calculated (73MI41101). This result was confirmed by another group (78MI4ll00>. Further, dipole measurements show similarly a large predominance of the asymmetric H-benzotriazole tautomer in benzene at 25 and 45 °C established by comparison with its 2-iV-methyl derivatives (74MI41100). 

This technique can be used extremely well to determine the geometry of the oxiranes. As long ago as the 1940s it was utilized in combination with dipole measurement to establish the bond lengths and bond angles in various substituted oxiranes. Similar data are found in the literature on deuterium-substituted oxirane. ... 

That pyridine species with decreased electron densities at positions adjacent to the nitrogen atom make significant contributions to the resonance hybrid even in the ground state has been shown by dipole measurements (12, 14). Interaction with a nucleophilic agent is consequently expected to follow a mechanism analogous to that involving o-chloronitrobenzene (Equation 4). 

It was suggested that a six-member chain of mannitol hexanitrate was coiled into a pseudo-ring. It is not surprising if one considers that long chain organic substances in solution have a tendency to be coiled. This is based on thermodynamical analysis, dipole measurements etc. 1124]. 

Miscellaneous—There have been several studies (mainly by i.r. spectra and dipole measurements) of donor complexes formed by derivatives of various... 

The conformation of derivatives of bicyclo[3.3.1]nonane has been the subject of many studies, based on proton nuclear magnetic resonance ( H-NMR), C-NMR, infrared (IR) and Raman spectroscopy, dipole measurements, X-ray crystallography, complexation experiments and various types of computational studies. Most of this work has been reviewed in detail (26,118, 119), and here we only report a summary of the general aspects. 

By H-NMR spectroscopy and dipole measurements, the 3,7-dimethyl-3,7-diazabicyclo[3.3.1]nonane (dimethylbispidine) 88 was shown to adopt a cc conformation with flattened wings (108). This was later confirmed by C-NMR spectroscopy and semiempirical molecular orbital (MO) calculations (EH, CNDO/2 the double-chair form was found to be more stable than the cb isomer by --83.8kJmoP and the bb form is even more destablized (133). This preference for cc is not due to solvent or packing effects since 88 has the same conformational preference in the gas phase, as shown by a computational study, which involved a scan of the potential energy surface (PES) and the calculated... 

Dihedral angles in solution have been computed from dipole measurements <78JOM(l46)235, 87PS(38)281> and in general the values are 20-30° higher than in the solid phase, perhaps because of enhanced butterfly-like motions. Selenanthrene, for example, appears to be considerably less sharply folded in benzene solution <83JCS(P2)li09>. 

Miscellaneous. Electronic effects within carbon-containing cyclophosphazenes (both NsPCa and NaPCs systems) have been investigated using various techniques such as electronic spectroscopy and dipole measurements, C1 n.q.r. spectroscopy and CNDO/2 calculations, and vibrational analysis. ... 

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