Reactions involving solvational

The introduction of hydroxide as a unique ligand into the inner-coordination sphere of solvated Cu(II) should diminish Jahn-Teller distortion and notably decrease the rate of inner-sphere substitution. This presumably accounts for the fact that no evidence has been found for a unique contribution of the Cu2(OH)2 " ion in reactions involving solvated Cu(II) up to pH 5.8 [162]. (At higher pH, Cu(OH)2 precipitates.)... 

In nonpolar solvents, exciplex formation is usually favored because of a small AG, and a favorable Coulombic term. The ions are likely to remain in intimate contact for a longer time, i.e., ion pairing is effective because of favorable Coulombic and solvent effects. That dissociation into solvent-separated is not likely for exciplexes formed in nonpolar solvents has been shown by extensive studies dealing with the photochemical additions of donor and acceptors. Reactions via exciplexes or CIP s frequently yield cycloadducts, whereas in polar solvents, coupling via substitution of radical ion pairs and other chemical reactions involving solvated radical ions may predominate [12]. 

Spectroscopic and kinetic aspects of reduction reactions involving solvated electrons have been reviewed together with those of radical anions. The dinitrogenruthenium(ii) complex Ru(NHa)5N2 + has been shown to be rapidly reduced by e in aqueous media to yield the corresponding ruthe-nium(i) complex, which has been characterized spectrally (Figure 2). This intermediate, however, decays to a species with a lower absorption via a second-order reaction... 

The stereochemistry of this reaction generally would have little effect on polymer tacticity in polymerization reactions involving solvated ion pairs or free ions because either the active endgroup would be free to rotate, or the counterion could move to a new location, 2,or both as shown in Equation 9. 

It is possible to detemiine the equilibrium constant, K, for the bimolecular reaction involving gas-phase ions and neutral molecules in the ion source of a mass spectrometer [18]. These measurements have generally focused on tln-ee properties, proton affinity (or gas-phase basicity) [19, 20], gas-phase acidity [H] and solvation enthalpies (and free energies) [22, 23] ... 

Reactions. The most noted magnesium alkyl reactions involve the solvated Grignard reagents. The more common reactions involving unsolvated magnesium alkyl are as foUows (14,15). 

Specific acid catalysis is observed when a reaction proceeds through a protonated intermediate that is in equilibrium with its conjugate base. Because the position of this equilibrium is a function of the concentration of solvated protons, only a single acid-dependent term appears in the kinetic expression. For example, in a two-step reaction involving rate-determining reaction of one reagent with the conjugate acid of a second, the kinetic expression will be as follows ... 

Many organic reactions involve acid concentrations considerably higher than can be accurately measured on the pH scale, which applies to relatively dilute aqueous solutions. It is not difficult to prepare solutions in which the formal proton concentration is 10 M or more, but these formal concentrations are not a suitable measure of the activity of protons in such solutions. For this reason, it has been necessaiy to develop acidity functions to measure the proton-donating strength of concentrated acidic solutions. The activity of the hydrogen ion (solvated proton) can be related to the extent of protonation of a series of bases by the equilibrium expression for the protonation reaction. 

Evidence that the actual methylation of the anion can be divided into SnI, Eq. (3), and Sx2 types, Eq, (4), is provided by a whole series of investigations. " The terms S l and 8 2 must be taken to mean reactions with, respectively less or greater nucleophilic participation of the anion in the transition state. The importance of oriented ion pairs" in the solvents of low polarity frequently used in reactions involving diazomethanc, e.g., the ions formed by a diazoalkane and benzoic acid in ether, should be emphasized. The expression oriented ion pair means that, because of insufficient solvation, the ions are not individually solvated but exist as ion pairs within a solvent cage. The orientation within the ion pair is defined electrostatically, and this orientation fixes the path for the productdetermining step. Several indications (cf, foo otes 22-24) in the literature indicate the occurrence of carbonium ions and oriented ion pairs in Broensted-type equilibria of the type of Eq. (2). 

In Sections III(l) and 111(2) the lability principle has been illustrated for processes involving the transfer of weakly bound electrons, including the reactions of solvated and trapped electrons and F-centers and processes of electrochemical generation of solvated electrons. In Sections IV and V, it will be illustrated also by atom transfer reactions and, in particular, by reactions involving adsorbed atoms. 

The formation of protonated H+(H20)n species can affect the acidity of the non-solvated protonic sites. Therefore, as the acid strength of the protonic sites in zeolites plays a key role in the hydrocarbon transformation reactions, driving the rate of the hydrocarbon protonation [4-6], the presence of water vapor among the reactants can modify reaction rates of the individual reactions involving in the hydrocarbon transformations. 

In what was intended as another experimental probe to ascertain whether a concerted or stepwise mechanism was involved in substitution reactions of arenesulfonyl chlorides, Rogne (1975) measured the enthalpies of transfer from propanol to acetonitrile for the transition states, SAH, for the reaction of imidazole with (a) benzoyl chloride and (b) benzenesulfonyl chloride. He found that SAH was considerably more negative for the reaction involving the sulfonyl chloride than for the one involving benzoyl chloride. This means that the transition state for attack of imidazole on benzenesulfonyl chloride is considerably better solvated by acetonitrile relative to its solvation by propanol... 

Figure 1. Constancy of AV for solvent exchange reactions where AV = —6.5 cm6/mol for Cr(DMF)63+-DMF solvent exchange at 338 K (a) and pressure dependence of AV for reactions involving charge development and, hence, solvational change where AV0 = —18.5 err /mol for Co(NH3)sSO/ direct aquation at 298 K (b).

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