Effective displacement

The Configuration Coordinate Model. To illustrate how the luminescent center in a phosphor works, a configurational coordinate diagram is used (2) in which the potential energy of the luminescent or activator center is plotted on the vertical axis and the value of a single parameter describing an effective displacement of the ions surrounding the activator, is plotted on the horizontal axis (Fig. 2). At low temperatures, near room... 

Novel polyester compositions have also been derived from dicyclopentadiene [77-73-6] (DCPD), which can enter into two distinct reactions with maleic anhydride to modify properties for lower cost. These compositions have effectively displaced o-phthaUc resins in marine and bathtub laminating apphcations. 

Although both cuprous and cupric fluorides have been studied in the past, an active fluorine donor can be formed from cupric oxide and hydrogen fluonde. This donor, in combination with 2,2 -bipyridine, effectively displaces the halogen of... 

The accelerative effect of London forces of attraction between a nucleophile and nearby substituents has been investigated in quinoline and benzene derivatives by Bunnett and co-workers, ii7b, 307 In 2-, 4-, and 6-arylsulfonyl-3-nitrochlorobenzene, Loudon and Shulman found that arylmercaptide ion, presumably through this effect, displaced the arylsulfonyl group while methoxide or ammonia displaced the nitro or chloro group. 

A variation on this theme consists in first displacement of the chlorine in 73 with ethylaminoethanol. Reductive amination of the ketone by means of ammonia in the presence of hydrogen gives the hydroxylated diamine (77). Use of this intermediate to effect displacement of the halogen at the 4 position of 70 affords hydroxychloroquine (78). ... 

Synthesis of all these heterocycle activated polyethers is carried out in polar aprotic solvents, such as NMPs, by the K2CO3 method. The effective displacement reactions are reported at varied temperatures (140-190°C) and durations (3-24 h). 

Various factors involved in both steps have been considered explicitly by Friedman and colleagues (29, 47, 49, 54, 67) to rationalize isotope effects in these reactions. Their treatment involves orientation effects, displacement isotope effects, and dissociation isotope effects in order to account for observed results. Stevenson and Schachtschneider (59) have also presented a treatment of decomposition isotope effects. 

Although most of the reactions to be considered under this head are net, i.e. overall, displacements or substitutions, this is not commonly achieved directly, cf. Sw2. In some cases a radical is obtained from the substrate by abstraction (usually of H), and this radical then effects displacement on, or addition to, a further species. In some cases, however, the net displacement is achieved by addition/abstraction. 

In one study, various distinct types of polar modifiers to n-hexane were tested for 3-chloro-l-phenylpropanol (3CPP) and 1-phenylpropanol (IPP) enantiomer separation [53]. Thereby, alcohol modifiers turned out to be more effective displacers of the solutes from the adsorption places on the sorbent surface, yet aprotic polar modifiers provided higher separation factors (with ethyl acetate in n-hexane affording the best separations for these chiral alcohols). It is evident, though, that the optimal choice of polar modifier is strongly solute dependent and can therefore not be generalized. 

Costantino et al. [75] have shown, however, that treatment with gaseous or aqueous HCl can lead to replacement of carbonate with chloride, which itself can be replaced by large organic anions such as methyl orange [79] or fluorescein [80]. It has recently been suggested that use of HCl/NaCl mixtures also leads to more effective displacement of carbonate by chloride [81]. 

Note that plots, such as Figure 5.1, provide information only on the net outcome of chemical reactions. In the case of iron, a small addition does take place in estuaries as a result of desorption of Fe from the surfaces of riverine particles. As these solids move through the estuarine salinity gradient, the major cation concentrations increase and effectively displace the iron ions from the particle surfeces. Since this release of iron is much smaller than the removal processes, the net effect is a chemical removal of iron. Sedimentation of these iron-enriched particles serves to trap within estuaries most of the riverine transport of reactive iron, thereby preventing its entry into the oceans. 

Keywords Anharmonic effects Displacive phase transition Isotope effects KDP-type ferroelectrics Order-disorder phase transition... 

Bromination of 3 -chloropropriophenone in dichloromethane generated the a-bromoketone 5, which, on treatment with 2-methyl-2-aminopropan-l-ol in acetonitrile, effected displacement of the bromide with concomitant cyclization to generate the racemic morpholinols 2. Addi lion of DTTA in industrial methylated spirit (IMS) gave the diastereoisomeric salts 2a and 2b, which were separated via crystallization. Subsequent treatment of the enantiomerically pure (S,S)-DTTA salt, 2a, radafaxine DTTA, with base gave a soluhon of radafaxine free base in ethyl acetate which was converted to the desired hydrochloride salt of the API on reaction with anhydrous hydrogen chloride (see Scheme 10.2). 

The reactivities of aryl halides, such as the halobenzenes, are exceedingly low toward nucleophilic reagents that normally effect displacements with alkyl halides and activated aryl halides. Substitutions do occur under forcing conditions of either high temperatures or very strong bases. For example, chlorobenzene reacts with sodium hydroxide solution at temperatures around 340° and this reaction was once an important commercial process for the production of benzenol (phenol) ... 

Reaction of compound A with lithium bromide in acetone effects displacement of the sulfonate leaving group by bromide with inversion of configuration. 

Roza and Berman 1971 Schott and McArdle 1974) and is used as an antidote in cases of acute barium poisoning. Calcium and magnesium suppress uptake of barium in vitro in pancreatic islets. Conversely, barium, in low concentrations, stimulate calcium uptake in these cells. Although the data are insufficient to determine the significance of these findings to human health effects, displacement of calcium may be the mechanism by which barium stimulates insulin release (Berggren et al. 1983). 

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