Displacement reaction defined

Reactions of this type are defined as sequential or single-displacement reactions. They can be either of two distinct classes ... 

It is usual to choose a container metal for fused salts sufficiently noble for the displacement reaction (2.16) to be negligible, and the most important aspects of corrosion are, as in aqueous solutions, those which involve reducible impurities, although in a salt melt there is also the additional possibility of a reducible anion (see above). All such factors can be described as controlling the oxidising power of the melt, which can be defined in terms of a redox potential just as in aqueous solutions The redox potential is expressed by relationships of the form... 

Sigma (a) bonds Sigma bonds have the orbital overlap on a line drawn between the two nuclei, simple cubic unit cell The simple cubic unit cell has particles located at the corners of a simple cube, single displacement (replacement) reactions Single displacement reactions are reactions in which atoms of an element replace the atoms of another element in a compound, solid A solid is a state of matter that has both a definite shape and a definite volume, solubility product constant (/ p) The solubility product constant is the equilibrium constant associated with sparingly soluble salts and is the product of the ionic concentrations, each one raised to the power of the coefficient in the balanced chemical equation, solute The solute is the component of the solution that is there in smallest amount, solution A solution is defined as a homogeneous mixture composed of solvent and one or more solutes. 

Defined stereochemistry at the anomeric carbon atom is also possible of achievement by means of displacement reactions at C-l (see equations 4 and 5). Only oligomers containing /3-d- (1—>6)-linkages were obtained when... 

Fig. 5-5. Schematic one-dimensional relative enthalpy diagram for the exothermic bimolecular displacement reaction HO + CH3—Br —> HO—CH3 + Br in the gas phase and at various degrees of hydration of the hydroxide ion [485]. Ordinate standard molar enthalpies of (a) the reactants, (b, d) loose ion-molecule clusters held together by ion-dipole and ion-induced dipole forces, (c) the activated complex, and (e) the products. Abscissa not defined, expresses only the sequence of (a). .. (e) as they occur in the chemical reaction. The barrier heights ascribed to the activated complex at intermediate degrees of hydration were chosen to be qualitatively consistent with the experimental rate measurements cf. Table 5-3 [485]. Possible hydration of the neutral reactant and product molecules, CH3—Br and HO—CH3, is ignored. The barrier height ascribed to the activated complex in aqueous solution corresponds to the measured Arrhenius activation energy. A somewhat different picture of this Sn2 reaction in the gas phase, which calls into question the simultaneous solvent-transfer from HO to Br , is given in reference [487].

Lemery defined precipitation as an expression chemists used to describe the fall of a body which had been suspended dissolved in a liquid from which it has been subsequently disunited. Although Fontenelle construed this as a physical definition based on the principles of hydrostatics, Lemery used it to differentiate true metallic precipitates, or the products of displacement reactions, from false ones. One could obtain false precipitates, or the matters that lost their initial metallic form and were reduced to a friable and indissoluble mass, in several ways. Calcination (red and violet mercury), incomplete dissolution in acids (antimony in spirit of salt or in regal water), and calcination after dissolution and evaporation (mercury in spirit of niter), all produced such precipitates. True metallic precipitates differed from false ones in that they were directly separated from their dissolution in liquid. As Lemery put it, false precipitates were abandoned by the liquid, while true precipitates abandoned the liquid themselves. True precipitates were made sometimes naturally through agitation, but mostly with recourse to the intermediates such as alkali salts or other metals. The choice of intermediates depended on the nature of the bodies to be precipitated. Lemery provided an exhaustive discussion for each case. In order to precipitate a resinous matter dissolved in spirit of wine, one could use common water which, by meshing intimately with the spirit, would precipitate the resinous matter. Camphor in spirit of wine could thus be... 

In double-displacement, or Ping-Pong, reactions, one or more products are released before all substrates bind the enzyme. The defining feature of double-displacement reactions is the existence of a substituted enzyme intermediate, in which the enzyme is temporarily modified. Reactions that shuttle amino groups between amino acids and a-keto acids are classic examples of double-displacement mechanisms. The enzyme aspartate aminotransferase (Section 23.3.1) catalyzes the transfer of an amino group from aspartate to a-ketoglutarate. 

Anchimeric assistance by the ring sulfur during nucleophilic displacement reactions at various ring positions have frequently been reported and could also be exploited for defined and desired structural alterations. 

Identity reactions (defined as reactions giving product identical with the reactant) are very useful for discussions of concerted nucleophilic displacements because they require that the transition structure lies on the tightness diagonal shown in the More O Ferrall-Jencks reaction map... 

The term synchronous is reserved to denote a mechanism where formation and fission occur to the same extent in the transition structure of a concerted mechanism the transition structure is anywhere on the diagonal dashed line (Figure 1). Bond order balance can be deduced from the changes in effective charge in the transition structure provided the charge is defined by the same standard dissociation equilibrium. This is illustrated by the displacement reaction of pyridines on 7V-phos-phopyridinium species (Scheme 4) the standard equilibrium for both bond formation and fission is the dissociation of substituted pyridinium ions (XpyH ) and hence the effective charges can be directly compared for both processes. 

Solvolytic displacement reactions can be affected by solvents in several ways, including nucleophilic solvent assistance (NSA) and electrophilic solvent assistance (ESA). NSA can be defined as electron donation from solvent to the developing positive dipole of a reacting C-X bond, and ESA can be defined as electron acceptance by the solvent from the leaving group, I. 

Glycosyltransferases can be broadly defined as enzymes that catalyze the transfer of giycosyi residues from their specific donor to an acceptor molecule." This is essentially a nucleophilic displacement reaction at a saturated carbon, the anomeric center. Most of these giycosyi transfer reactions occur between two oxygen... 

Hydrolysis is an example of a larger class of reactions referred to as nucleophilic displacement reactions in which a nucleophile (an electron-rich species containing an unshared pair of electrons) attacks an electrophilic atom (an electron-deficient reaction center). Hydrolytic processes encompass several types of reaction mechanisms that can be defined by the type of reaction center (i.e., the atom bearing the leaving group, X) where hydrolysis occurs. The reaction mechanisms encountered most often are direct and indirect nucleophilic substitution and nucleophilic addition-elimination. 

More well-defined iron compounds have also been used as catalyst precursors for aldehyde and ketone hydrosilylation. Nikonov [110] reported that [(Tl -C5H5)Fe(PR3)(CH3CN)2] is an active hydrosilyation catalyst, although the substrate scope has yet to be explored. Using a ligand displacement reaction originally pioneered by Campora and coworkers [111], our laboratory reported that... 

Ligand displacement reactions with these phosphino ligands and transition metal complexes showed that only from the mono- and the two ortAo-functionalized octafalkyl/halogenalkylsilses-quioxanes) it is possible to build defined complexes (Eq. 1) [8]. 

The compressive load is applied to the ends of the specimen by the crosshead of a testing machine. The bottom part of the testing machine remains static and provides a reaction force to the bottom end of the stiffener. The longitudinal displacement is defined as the displacement of the crosshead towards the static table and was measured with a transducer. The out of plane displacement was also measured with a transducer, which permitted the buckling shape of the plating side of the stiffener at mid-length to be monitored. 

When displacement reactions are associated with electroless deposition of silver, exotic coaxially-organized heterostructures, characterized by hybrid chemical compositions, are generated [17, 125]. The heterostructures present a concentric topology of the various metals, a sort of Matrioshka arrangement known as nanorattles as defined by the same authors [17], Different shape and material configurations have been reported in literature, for instance onto spherical AuAg alloy core NCs, Ag could be deposited by chemical reduction promoted by ascorbic acid at high temperatures and water environment, afterwards, a redox displacement HAuCU-promoted altered the silver shell composition... 

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