1.3- dipole nature

Nicholson, H., Becktel, W.J., Matthews, B.W. Enhanced protein thermostability from designed mutations that interact with a-helix dipoles. Nature 336 651-656, 1988. 

Where solvent exchange controls the formation kinetics, substitution of a ligand for a solvent molecule in a solvated metal ion has commonly been considered to reflect the two-step process illustrated by [7.1]. A mechanism of this type has been termed a dissociative interchange or 7d process. Initially, complexation involves rapid formation of an outer-sphere complex (of ion-ion or ion-dipole nature) which is characterized by the equilibrium constant Kos. In some cases, the value of Kos may be determined experimentally alternatively, it may be estimated from first principles (Margerum, Cayley, Weatherburn Pagenkopf, 1978). The second step is then the conversion of the outer-sphere complex to an inner-sphere one, the formation of which is controlled by the natural rate of solvent exchange on the metal. Solvent exchange may be defined in terms of its characteristic first-order rate constant, kex, whose value varies widely from one metal to the next. 

If the transition is of an electric dipole nature, the interaction Hamiltonian can be written as // = p E, where p is the electric dipole moment and E is the electric field of the radiation. The electric dipole moment is given by p =, where r is the... 

Dipole polarization-effect moisture sensors utilize the electrical asymmetry around the water molecule (two slightly positively charged H2 atoms and a slightly negatively charged 02 atom). When these molecules are subjected to an electric field, they tend to align with the electric field because of their dipole nature. At a frequency of 20 kHz, moisture can be detected by this method. 

The angular dependence is a direct result of the dipole nature of the plasmon polarization, the excitation polarization, and the directionality of the transition dipole moment. This is the most difficult parameter to predict and control, especially in multimode plasmon suppcxting substrates. In addition, as shown in the previous section, there is competition between the rate of nonradiative energy transfer and the effective field enhancement. Hence, for each fluorophore-nanostructure combination there is a delicate balance to be found. Therefore, finding the optimal distance from the enhancing surface is essential for maximizing SEF. 

The dipole nature of oscillators is also confirmed by other methods (for further details see Ref. ). 

To emphasize the dipole nature of the HF molecule, the formula can be written as H " F . The symbol 6 is a lowercase Greek delta, which is used in science and math to mean partial. With polar molecules, such as HF, the symbol 6" is used to show a partial positive charge on one end of the molecule. Likewise, the symbol 6 is used to show a partial negative charge on the other end. 

The answer is b. (Murray, pp 15-26.) Water molecules have a dipole nature and dissolve salts because of attractions between the water dipoles and the ions that exceed the force of attraction between the oppositely charged ions of the salt. In addition, the latter force is weakened by the high dielectric constant of water. Nonionic but polar compounds are dissolved in water because of hydrogen bonding between water molecules and groups such as alcohols, aldehydes, and ketones. 

Neutral molecules form very much weaker complexes with crown ethers usually as a result of (O-H O), (N-H O), and (C-H O) hydrogen bonding of a dipole-dipole nature involving respectively OH-, NH-, and CH-acidic guest species [23]. Examples are provided in Fig. le and f respectively by the X-ray crystal structures [24,25] of (i) a 1 1 complex (5) (HjO) formed between a bisdi-C>-methyl-ene-D-mannitolo-22-crown-6 derivative (5) and water and (ii) a 1 2 complex (2) [(Me2S02)2l formed between 18-crown-6 (2) and dimethyl sulphone. The former has... 

Once the electric or magnetic dipole nature of the transitions is known, selection rules are determined from group theory. The components of the electric and magnetic field vectors transform according to definite representations of the point group (often different ones, as E is a polar vector and B is an axial vector). A particular transition is allowed (forbidden) if the irreducible representation of the final state is (is not) contained in the Kronecker product of the initial state representation and the representation of the appropriate component of E or B (Tinkham, 1%4). 

If solvation is regarded as the interaction of ions and solvent molecules of dipole nature (i.e., if the specific coordination chemical nature of the solvation is disregarded), ion-pair formation can even be described quantitatively. To a first approximation, the dependence of the equilibrium constant (K) of ion-pair formation is given, on the basis of the electrostatic model, by the equation... 

In the outer sphere of metal halide complexes, the solvent molecules may be partially hydrogen-bonded to the halide ligand, and partially (as a consequence of their dipole nature) in electrostatic interaction with the complex anion. 

In a molecule, there may be local dipoles and single charges in the meaning that the counter charge is far away. Electrostatic forces will occur that basically are of a charge-to-dipole or dipole-to-dipole nature. These forces will be intermolecular and intramolecular and will therefore influence the geometrical form of the molecule. 

Hydration of ions is due to the dipole nature of water. In the case of a cation in water, the negative (oxygen) end of the neighboring water molecules will be oriented toward the ion, and a sheet of oriented water molecules will be formed around the cation. This sheet is called the primary hydration sphere. The water molecules in the primary hydration sphere will furthermore attract other water molecules in a secondary hydration sphere, which will not be as rigorous as die primary sphere. Several sheets may likewise be involved until at a certain distance the behavior of the water molecules will not be influenced by the ion. 

It is interesting that in HCl and HBr, which already possess quite considerable dipoles, there is an appreciable deviation in the sense that the lattice energy calculated on the basis of dispersion force alone is too small, because interactions of a dipole nature intervene. The fact, however, that in these lattices the quantum mechanical forces play a very important part is clear from the data in Table 62 and from the calculations of Born and Kornfeld, who for a long time have tried to adopt a true... 

A-chloronicotinamide (NCN) oxidation of chalcones to benzoic acid (BzA) in ACOH-H2O (80-20%) in the presence of HCl and CIO4" ion is first order in NCN and zero order in BzA the rate increases with [H" "] and increasing percentage of AcOH. A plot of log versus HD is linear with a positive slope indicating the ion-dipole nature of the reaction. ... 

The two Formal Graphs in Graph 9.4 model the most general dipole assemblies using only one common node which are composed of the three natures of dipoles simultaneously. Simpler Formal Graphs using fewer properties are drawn when a lower number of dipole natures form the assembly, as will be shown in this chapter. 

The complex macromolecule represented by the network of protein fibres in the cytoplasm is maintained intact by a series of jimctions between polypeptide chains (see p. 99). Certain of these linkages are homopolar in nature, for example the disulphide bonds. Others are joined by heteropolar bonds, or salt linkages. In addition there are cohesive bonds between nonpolar groups (for example attraction between CH3 groups) and polar groups (for example attraction between groups of a dipole nature). 

Optical transitions between 4f" levels used for optical pumping and stimulated emission are predominantly of electric-dipole nature. Although f-f transitions are forbidden by Laporte s rule, if the rare earth is located in a non-centrosym-metric site, odd-order terms in the expansion of the static (or dynamic) crystal-field admix states of higher, opposite-parity configurations, such as 4f" 5d, into 4f" and transitions become allowed. The oscillator strengths of transitions between J states are small, 10 . - While ab initio calculations of the probabilities for electric-dipole transitions are not possible, spectral intensities can be treated using the Judd-Ofelt approach discussed below. 

It is known that water is a dipolar molecule. The oxygen-end of a water molecule forms the negatively charged end and the hydrogen-end, the positively charged end. Due to the dipole nature, the water molecule is attracted towards the electrode and contributes to the potential difference across the double layer. The orientation of the water molecule depends on the charge on... 

Customarily, it is assumed that e is unity and that ]l = p,cos 9, where 0 is the angle of inclination of the dipoles to the normal. Harkins and Fischer [86] point out the empirical nature of this interpretation and prefer to consider only that AV is proportional to the surface concentration F and that the proportionality constant is some quantity characteristic of the film. This was properly cautious as there are many indications that the surface of water is structured and that the structure is altered by the film (see Ref. 37). Accompanying any such structural rearrangement of the substrate at the surface should be a change in its contribution to the surface potential so that AV should not be assigned too literally to the film molecules. 

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