Ions, donor

Xenon tetrafluoride is a much weaker fluoride ion donor and only forms stable complex salts with the strongest fluoride ion acceptors, eg,... 

KURSANOV PARNES Ionic Hydrogenation A non-calalytK hydrogenation of C C. C O, C N bonds and hydrogenotysis of C-OH, C Hal etc, under the action of an acid and a hydride ion donor... 

It has also been found that halide-ion donors (such as X in A1X4 and GaX4 ) are more than... 

Alternatively, within the Lewis formalism, acids are fluoride-ion acceptors. The prime examples are AsF- and SbFs (which give MF ) and to a lesser extent BF3 which yields BF4 ". A greater diversity is found amongst Lewis bases (fluoride-ion donors), typical examples being XeFg, SF4, CIF3 and BrF3 ... 

Lewis acid (fluoride-ion acceptor) behaviour is exemplified by reactions with NOF and MF to give [N0]+[C1F2] and M+[C1F2] respectively (M = alkali metal or NH4). Lewis base (fluoride ion donor) activity includes reactions with BF3 and ASF5 ... 

The compounds can therefore be used as nonaqueous ionizing solvent systems (p. 424). For example the conductivity of ICl is greatly enhanced by addition of alkali metal halides or aluminium halides which may be considered as halide-ion donors and acceptors respectively ... 

Liquid CIF3 can act both as a fluoride ion donor (Lewis base) or fluoride ion acceptor (Lewis acid) to give difluorochloronium compounds and tetrafluorochlorides respectively, e.g. ... 

IF7 acts as a fluoride ion donor towards AsFs and SbFs and the compounds [IF6]" [MF6] have... 

Michael reactions take place by addition of a nucleophilic enolate ion donor to the /3 carbon of an a,(3-unsaturated carbonyl acceptor, according to the mechanism shown in Figure 23.7. 

A Michael reaction involves the conjugate addition of a stable enolate ion donor to an o,/3-unsaturated carbonyl acceptor, yielding a 1,5-dicarbonyl product. Usually, the stable enolate ion is derived from a /3-diketone, jS-keto ester, malonic ester, or similar compound. The C—C bond made in the conjugate addition step is the one between the a carbon of the acidic donor and the (3 carbon of the unsaturated acceptor. 

Polar aprotic solvent (Section 11.3) A polar solvent that can t function as a hydrogen ion donor. Polar aprotic solvents such as dimethyl sulfoxide (DMSO) and dimethyl-formamide (DMF) are particularly useful in Sn2 reactions because of their ability to solvate cations. 

These measurements indicate that it is not possible to identify a single value of pe surrounding the O2/H2S interface in the environment. Redox couples do not respond to the pe of the environment with the same lability as hydrogen ion donors and acceptors. There is no clear electron buffer capacity other than the most general states of "oxygen containing" or "H2S containing." The reason for the vast differences in pec in the oxic waters is the slow oxidation kinetics of the reduced forms of the redox couples. The reduced species for which the kinetics of oxidation by O2 has been most widely studied is Mn. This oxidation reaction... 

Let us consider a case in which an ion (donor, D ) and a solvent (acceptor. A) form a CT complex. The ground state energy (see Fig. 5) can be obtained as a solution of the secular equation ... 

As in the case of C1F, the trifluoride can behave as both a fluoride ion donor and acceptor, as illustrated by the reactions carried out in liquid C1F3 ... 

In the above reactions both MgO and CaO are the oxide ion donor and hence act as bases, whereas Si02 and S03 are the oxide-ion acceptor and hence act as acids. Ultimately, the Lux-Flood acid and base react to form magnesium silicate (MgSi03) and calcium sulphate (CaS04) salts respectively. 

The hydrofluoride of a proton sponge is used in MeCN as fluoride ion donor benzoyl chloride is transformed into benzoyl fluoride107 (reaction 10). 

Ionic hydrogenation reactions85 involve the use of a hydrogenating pair consisting of a proton donor and a hydride ion donor. The ionic hydrogenation is based on the principle that the carbenium ion formed by the protonation of the double bond abstracts a hydride ion from the hydride source. 

A theoretical formalism is available for understanding optical charge transfer processes in a variety of chemical systems (mixed-valence ions, donor-acceptor complexes, metal-ligand charge transfer chromophores, etc) where the extent of charge transfer is large and where electronic coupling between the electron donor and acceptor sites is relatively small. 

Assuming that an isolated gaseous ion X is at the reference zero energy level as shown in Fig. 3-1, we define the occupied energy level of X ion (the unitary X ion donor level, molecule XY by the negative ionic dissociation... 

Although many other acid-base definitions have been proposed and have been useful in particular types of reactions, only a few have been widely adopted for general use. Among them are those attributed to Arrhenius (based on hydrogen and hydroxide ion formation), Br0nsted-Lowry (hydrogen ion donors and acceptors), and Lewis (electron pair donors and acceptors) [6,67-70]. 

The promise of luminescent methodology is based on many types of information that can be derived from mineralogical samples. These include RE from Ce to Yb, identities down to the ppb range, the valence states of the RE, the nature of the sites at which RE reside and the ways of compensating the charge, and features related to the presence of other ions (donors, activators). All this information can be used to determine the chemical, thermal, and deformational history of the material. 

Figure 1. Postulated formation of a-dialkylamino nitrite esters (I) from immo-nium ion donors and their fragmentation to nitrosamines...

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