Equivalent, electro-chemical

Electrochemical Equivalent number of moles of substance reacted electro-chemically by the passage of 1 Faraday of charge. 

Organosulfur compounds are especially useful for C-fluorine bond forming reactions with (difluoroiodo)arenes. For example, dithioketal derivatives of benzophenones are readily converted to diaryldifluoromethanes with two equivalents of DFIT in dichloromethane [105]. This transformation has also been effected with electro chemically prepared p-(difluoroiodo)anisole/Et3N 3HF, and by anodic oxidations of p-iodoanisole in acetonitrile solutions containing Et3N 3HF and dithioketal substrates (Scheme 35) [96]. Under the latter conditions, p-(difluoroiodo)anisole is continuously regenerated, and the iodoarene was employed at catalytic levels for high yield conversions of the dithioketals to diaryldifluoromethanes. 

These concepts are developed in greater detail in Chap. 7 of W. Stumm and J. J. Morgan, Aquatic Chemistry, Wiley, New York, 1981. As with any single-ion activity, it is always possible to relate the electron activity to a chemical potential formally (see, e.g., Eq. s2.22) and thus define an equivalent electrochemical emf (see Eq. s2.23). Accordingly, the (electro)chemical potential of an electron in aqueous solution is related to the pE value by the equation (see Special Topic 2) ... 

Faraday ( 662) says he had considered the subject with two friends , but the now familiar names were coined for Faraday by William Whewell, later master of Trinity College, Cambridge, who is not mentioned, probably at his own request. After the paper was read in February, some names were altered, as appears from Faraday s dairy (F). The name electro-chemical equivalents appears on 23 September 1833. On 19 December 1833 Faraday used the name electrobeids (palvo), I go) for ions. Electrode appeared on 17 December 1833, positive and negative (P. and N.) electrodes frequently after this. In February 1834 Faraday used the name zetode (enclitic particle , motion towards). Whewell s names appear first on 13 May 1834. In letters to Faraday dated (i) 25 April and (2) 5 May, 1834 Whewell says ... 

The intermediacy of silylenes, equivalent to carbenes, is suggested from hindered dichlorosilanes, e.g., dimesityldichlorosilane.2i6 Their sonochemical dimerization gives tetramesitylsilene in ca, 90% yield instead of 20% electro-chemically. The reaction of di-f-butyldichlorosilane, in the presence of triethyl-silane as a trapping agent, gives mainly the symmetrical disilane with sodium or potassium but also the product of insertion into the Si-H bond with lithium, in 85% yield. In the presence of an olefin, the intermediate is trapped to give silacyclopropanes stereoselectively.2i7 Sonication is essential for success. 

Faraday s final version of the first law of electro-chemistry, enunciated in 1834, states "The chemical power of a current of electricity is in direct proportion to the absolute quantity of electricity which passes". I shall leave discussion of his work on the second law which states "Electro-chemical equivalents coincide, and are the same, with ordinary chemical equivalents" Q) to another paper. Also, since most of the modern electro-chemical terminology was coined by Faraday during the experimental work which led to his enunciation of these laws, it would be inappropriate to apply these terms to period before he defined them (4). 

The harmony which this theory of the definite evolution and the equivalent definite action of electricity introduces into the associated theories of definite proportions and electro-chemical affinity, is very great. According to it, the equivalent weights of bodies are simply those quantities of them which contain equal quantities of electricity, or have naturally equal electric powers it being the ELECTRICITY which determines the equivalent number, because it determines the combining force. Or, if we adopt the atomic theory or phraseology, then the atoms of bodies which are equivalents to each other in their ordinary chemical action, have equal quantities of electricity naturally associated with them."... 

When the impedance plot is sufficiently detailed and the various contributions resolved, one can determine the various resistances, capacitance, and diffusion process parameters. Care must be taken in analyzing the data as different equivalent circuits can yield the same or very similar impedance plots. ° It may therefore be meaningless to use sophisticated programs for fitting complicated equivalent circuits comprising many elements and to look for best fit if the data are not sufficiently accurate, which is usually the case. It is then advisable to guess an as simple equivalent circuit as possible that can be justified electro-chemically for describing the supposed processes in the cell and fit its parameters. 

The fundamental electronic disorder reaction is equivalent to the overcoming of the gap between valence band and conduction band and, hence, represents the generation of conduction electrons e (in the conduction band) and holes h (in the valence band). Relations between the (electro-) chemical potentials of defects (e, h) and components (e ) are analogous to the ionic case (see below). 

In dendrimers based on metals as branching centers (Fig. 1 d), the electrochemical behavior is even more complex since (i) each unit of the dendrimer is electro active, (ii) the chemical nature of the metal-based units constituting the dendrimer may be different, (iii) chemically equivalent units can be different from the topological viewpoint, and (iv) the degree of interaction among the moieties depends on their chemical nature and distance. 

A rigorous electro-nuclear separability scheme has been examined. Therein, an equivalent positive charge background replaces the nuclear configuration space the coordinates of which form, in real space, the -space. Diabatic potential energy hypersurfaces for isomers of ethylene in -space were calculated by adapting standard quantum chemical packages. 

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