Excess dipole moment

G. C. Pimentel (Berkeley) In discussing the excess dipole-moment induced by the formation of an H bond, Professor Coulson has noted that the necessary value of Z e9 the effective proton charge, is 2-3. I wonder if this is a rather high estimate of the necessary effective charge because the centre of gravity of the non-bonding electrons is closer to the proton than is the oxygen atom ... 

FIGURE 2-4 The relation between the square of excess dipole moment (Aii) , and K (25 C). 

The equation applies to dipoles in firee space, whereas in reality the particles might be embedded in an arbitrary medium with relative permittivity s ,. The following sections consider only the additional scattering effect by the particles, which means only the excess dipole moment pexc is of further relevance ... 

Figure 4 The excess dipole moment along the z-direction perpendicular to the water-hexane interface. The aqueous phase is to the left, the hexane phase is to the right, and the interface is located at...

Pure TeNMe is said to be colorl, but becomes yellow on contact with w, due to hydrolysis to TNMe (Ref 5). Mp 14.2° (Ref 26) bp 125.7° (Ref 10) d at 25°, 1.62294g/cc RI at 25°, 1.43822 (Ref 18). The dipole moment is essentially zero, indicating the structure to be symmetric, instead of (02N)sC0N0 as had been postulated to account for its reactivity (Ref 18) CA Registry No 509-14-8 Historical It was first prepd by the action of nitric acid on TNMe (Ref 2). This reaction is the basis of large scale prepn in which acetylene is nitrated to TNMe and the latter treated with an excess of nitric acid to give TeNMe (Ref 26). 

Some examples will illustrate the application of the theory to particular molecules. In toluene, the observed direction of the dipole moment shows that electrons have baen transferred from the methyl group to the ring. Hence substitution takes place readily, particularly at the o- and -positions, which have the greatest excess of electrons. 

At a phase boundary (or interface) the molecular species experience anisotropic forces, which vary with the distance from the interface. This causes a net orientation of solvent and other molecular dipoles and a net excess of ions near the phase boundary, on both sides of the solution. The term electrified interface means that there occur differences in potential, charge densities, dipole moments, and electric currents. 

Experimental dipole moments and acidities of azoles, including 1,2,3-triazole, show linear correlations with their Jt-electron excess calculated by the semiempirical AMI method <2003CHE71>. Experimental dipole moments of azoles agree well with those calculated by the DFT program ALLCHEM <2003PCA4172>. Calculated dipole moments t (in units of Debye,D) of a few selected azoles are listed below ... 

The electrosorption valence can be related to the dipole moment of an adsorbed species introduced in Chapter 4. For this purpose consider an electrode surface that is initially at the pzc and free of adsorbate. When a small excess charge density o is placed on the metal, its potential changes by an amount A given by ... 

To obtain the dipole moment we set o = —o% in Eq. (18.14) so that the diffuse double layer is free of excess charge (see Section 4.3). 

The linear solvent strength (LSS) model combined with QSRR calculations has been applied for the prediction of retention in gradient RP-HPLC. It was established that total dipole moment (jd), electron excess charge of the most negatively charged atom (<5Mm) and water-accessible molecular surface area (Awas) exert the highest impact on the retention ... 

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