Donor-acceptor process

A wide class of aiyl-based quaternary surfactants derives from heterocycles such as pyridine and quinoline. The Aralkyl pyridinium halides are easily synthesized from alkyl halides, and the paraquat family, based upon the 4, 4 -bipyridine species, provides many interesting surface active species widely studied in electron donor-acceptor processes. Cationic surfactants are not particularly useful as cleansing agents, but they play a widespread role as charge control (antistatic) agents in detergency and in many coating and thin film related products. 

Senesi and Testini [147,156] and Senesi et al. [150,153] showed by ESR the interaction of HA from different sources with a number of substituted urea herbicides by electron donor-acceptor processes involves organic free radicals which lead to the formation of charge-transfer complexes. The chemical structures and properties of the substituted urea herbicides influence the extent of formation of electron donor-acceptor systems with HA. Substituted ureas are, in fact, expected to act as electron donors from the nitrogen (or oxygen) atoms to electron acceptor sites on quinone or similar units in HA molecules. 

In doped polymers, hole or electron transport occurs by the transfer of charge from states associated with the donor or acceptor molecules, respectively. This can be described as a one-electron oxidation-reduction or donor-acceptor process between molecules in their neutral charged states (Pfister, 1977 Mort and Pfister, 1979 Pai et al., 1983 Facci and Stolka, 1986). For hole transport, some dopant molecules are initially positively charged (cation radicals). Under an applied field, neutral molecules will transfer electrons to the cation radicals. This results in the motion of positive charge. For this to occur, the dopant molecules must be donor-like in their neutral state. For electron transport, electrons are displaced from the anion radicals to neutral molecules, which requires that the dopant molecule be acceptor-like in its neutral state. It is generally accepted tliat these processes occur by hopping. 

The chloride ion is not attached directly to the nitrogen but is held simply through electric forces by the ammonium ion/ The two valence spheres of Werner s complexes thus had a simple explanation. The inner valences were electron pair bonds often formed by the donor-acceptor process. The outer valences were electrovalent in character. 

Ihe interaction between atoms and molecules can vary from the weak attraction between a pair of closed-shell atoms (e.g. two rare gas atoms in a molecular beam) to the large energy associated with the formation of a chemical bond. Intermediate between these two extremes are interactions due to hydrogen bonding or electron donor-acceptor processes. In these intermediate cases it is often difficult to determine what factors are important in contributing to the interaction. For example, what can a hydrogen bond be ascribed to ... 

Features of Adhesive Interaction in Liquid Media. The adhesion of particles in liquid media has a number of special features in comparison with adhesion in air. These features are determined by the fact that the dust-covered surface is surrounded by liquid rather than air. The liquid medium changes the nature of the adhesive forces. Capillary and electrical forces (see Sections 15-17) do not appear in liquid media. Any charges that are on the particles will leak off in a liquid medium, and donor-acceptor processes do not take place on the wet surface. No capillary forces will be manifested since no liquid bridge (meniscus) tending to draw up the adherent particle can be formed in the contact zone. 

Another definition used in ionic melts concerns donor-acceptor processes with the transfer of oxide ions,. Since 1939, when Lux proposed to define acids as oxide ion acceptors and bases as donors of such kind of acid-base interactions became to be known as... 

Chromogenic development process, 1, 369-373 Chromogens donor-acceptor, 1, 329 Chromoglycic acid sodium salts... 

Deviations from Raonlt s law in solution behavior have been attributed to many charac teristics such as molecular size and shape, but the strongest deviations appear to be due to hydrogen bonding and electron donor-acceptor interac tions. Robbins [Chem. Eng. Prog., 76(10), 58 (1980)] presented a table of these interactions. Table 15-4, that provides a qualitative guide to solvent selection for hqnid-hqnid extraction, extractive distillation, azeotropic distillation, or even solvent crystallization. The ac tivity coefficient in the liquid phase is common to all these separation processes. 

Although the electrostatic potential on the surface of the polyelectrolyte effectively prevents the diffusional back electron transfer, it is unable to retard the very fast charge recombination of a geminate ion pair formed in the primary process within the photochemical cage. Compartmentalization of a photoactive chromophore in the microphase structure of the amphiphilic polyelectrolyte provides a separated donor-acceptor system, in which the charge recombination is effectively suppressed. Thus, with a compartmentalized system, it is possible to achieve efficient charge separation. 

There is a third method proposed for classifying colorants which is in terms of the mechanism of the electronic excitation process. According to this method, organic colorants may be classified as donor acceptor, polyene, cyanine or n-rc chromogens. While this method of classification is undoubtedly of importance theoretically, it is arguably of lesser practical importance, since the vast majority of commercial organic dyes and... 

The photogalvanic effect is based on light absorption by a suitable photoactive redox species (dye) in the electrolyte solution. The photo-excited dye subsequently reacts with an electron donor or acceptor process, taking place in the vicinity of an electrode, is linked to the electrode... 

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