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It is shown that the enhanced Raman spectra of pyridine adsorbed on Fe can be obtained by depositing thin films of Fe onto roughened Ag substrates. An alternative strategy of inducing enhanced scattering is also explored which relies on the deposition of a low density of small growth centres of Ag on Fe by simple displacement reaction followed by dissolution of the smooth substrate; this procedure gives electrodes which show spectra both of Ag and/or Fe depending on the position of illumination.

In this paper the kinetics of initial nitridation of thermal oxides is studied by using rapid thermal nitridation of thin oxides. FTIR and AES were used to investigate the chemical properties of nitrided oxide films. The amount of the nitrogenincorporated in and the oxygen escaped from 100Å oxides has been characterized quantitatively as a function of RTN conditions. Results show that RTN at 1100° for 120s incorporates about 85% and 12% of the maximum nitrogen concentration value at oxide surface and bulk, respectively. The nitrogen pile up peak at interface can be seen after RTN at 1100°C with the time as short as 5 s. Study of the effects of the nitridation temperature and the original oxide film thickness indicates that the reaction species has permeated through oxides before effective replacement reaction takes place. The diffusion coefficient of the permeating species is estimated of the value larger than 40−13cm2/s.

The replacement reaction of myoglobin (Mb), MbCO + O2 leads to MbO2 + CO leads to MbCO + O2, has been studied with flash photolysis in the temperature range from 140 to 320 K and the time range from 2 mus to 200 s. In a fraction of the Mb, the photodissociated CO remains within the protein; rebinding is not affected by the presence of O2 and occurs with rates that are identical with the ones observed earlier in solvents containing only CO. In the remaining fraction CO migrates into the solvent and Mb combines preferentially with oxygen. The rate of the subsequent replacement of O2 by CO permits calculation of the oxygen dissociation rate ko2; ko2 has been determined from 260 to 320 K. The measurements support a multibarrier model.

Ten bis(4-aryloxy-3-nitrophenyl) sulfones were synthesized via a phase-transfer catalyzed, nucleophilic displacement reaction involving phenoxides and bis(4-chloro-3-nitrophenyl) sulfone.

A new, very useful application of open—closed configurations to kinetic studies is reported. The multipeak recordings provided by the manifold used, which features a single conventional photometric detector, were used to calculate the rate constants and reaction orders of a chemical system, namely the ligand displacement reaction between the cobalt(II)—EGTA complex and PAR.

Crotylmagnesiuin halide and nickelocene (molar ratio Mg/Ni~100) catalyze the dimerization of butadiene to 3-methyl-1.4.6-heptatriene arid the triroerization to 1-exo-methylene-2-methyl-4.6-divinyl-cyclohexane. Isoprenylmagnesiuinhalide and nickelocene catalyze the dimerization of isoprene to a mixture of 3.3.6- and 2.3.6-trimethyl-1.4.6-heptatriene. On the basis of model reactions, the catalytic processes are suggested to occur through a sequence of Mg-C addition to C=C, exchange of allyl groups between Mg and Ni followed by displacement reactions in CpNi-П-allyl complexes or CpNi-alkyl intermediates by the 1.3-diene.

The growth and morphology of reaction layers in diffusion couples is probably more frequently influenced by impurities than is generally realized. We found drastic effects of impurities on the reaction between Cu and Si and on the reaction between Cu20 and Ni or Co. In the first case the always present thin Si02-film on Si plays an important role: it hampers the reaction between Cu and Si, giving rise to an incubation period. This reaction barrier can be removed completely by only a few ppm of phosphorus in the copper starting material, which enables the formation of Cu3Si at much lower temperatures than in the absence of phosphorus. In the latter example the presence of chloride ions prevents NiO or CoO, which is formed during the displacement reaction, from building up a continuous, closed and rate-limiting layer. Instead, precipitates of these oxides in a matrix of copper are formed . This results in a much higher reaction rate since then the much faster diffusion of oxygen through copper becomes rate-limiting.

The synthesis and properties of some of the first examples of boron analogues of the α-amino acids are presented. Conversion of amine-cyanoboranes to amine-carboxyboranes (boron analogues of amino acids) is described. The synthesis of the boron analogue of glycine, H3NBH2CO2H, from an amine displacement reaction on Me3NBH2CO2H is discussed and its x-ray crystal structure given. These boron analogues, their precursors, derivatives, and related compounds have exhibited significant antiarthritic, anti-inflammatory, anti-tumor, antihyperlipidemic and other biological activity in screens using animal models. The results of these studies are summarized in this paper.

Alkylation of nylon produces nylon imidate, which is used for the covalent coupling of enzymes and other proteins and ligands. Nylon imidate is unusually stable when stored wet, with a half-life of about 60 days. Reaction with enzymes has an optimum about pH 7-8 and is extremely rapid, with about 60% of the reaction being complete in the first 10 min. The amidine formed in reaction with an amino group can be displaced by another nucleophile. In view of this finding that nylon amidine is capable of exchanging proteins, it is now concluded that nylon-tube reactors containing immobilized enzymes made by this method may not be used as extracorporeal shunts or as on-line monitors on patients, since the enzyme in the reactor may be released into the circulation by nucleophiles in the blood. This can lead to complications. The chemistry of this displacement reaction is discussed.

New methodology is described for the construction of tricyclic heterocycles. Thus, a double displacement reaction of l-(2-fluorobenzoyl)-2-methylthio-2-imidazoline (8a) with 1,1-dialkylhydrazines gave 10-substituted 2,10-dihydroimidazo[2,1-b]quinazolin-5(3H)-ones in good yield. The corresponding 1-(2-nitrobenzoyl)-2-meth-ylthio-2-imidazolines also underwent double displacement reactions with hydrazines. Other tricyclics made using double displacement reactions were pyrimido[2,1-b]quinazolines, imidazo[1,2-a]pyrido[2,3-d]pyrimidines, and imidazo[1,2-a]pyrazolo[3,4-d]pyrimidines. Treatment of 8a with hydrazine hydrate or methylhydrazine gave products resulting from displacement, but did not afford fused benzotriazepinones.

Surface segregation and oxidation of Cu-9.7at%Ni-2.3at%Sn and Ag-39at%Cu-1.6at%Ge ternary alloys have been carried out employing XPS and AES techniques. Segregation of both Ni and Sn have been observed on the surface of Cu-Ni-Sn alloy. On oxidation of this alloy at 500 K, $Cu_2O$, NiO and SnO have been observed and on heating the oxidized alloy in vacuum to 600 K, $Cu_2O$ was reduced to Cu through a displacement reaction involving Ni. Further heating to 750 K showed only $SnO_2$, along with the reduction of NiO to Ni. The Ag-Cu-Ge alloy showed segregation of both Ag and Ge to the surface. On oxidation at 500 K, only $Cu_2O$ and GeO have been observed. Heating of the oxidized surface to 700 K in vacuum showed desorption of GeO, coupled with the reduction of $Cu_2O$ to Cu. thereby leaving the alloy surface clean.

1,3,4-Thiadiazol-2-ylacetic acids 4 were prepared by lithiation of 2-methyl-1,3,4-thiadiazoles 1, followed by treatment with carbon dioxide. Diethyl 1,3,4-thiadiazol-2-ylmalonates 6 were prepared by nucleophilic displacement reaction of the corresponding bromides 5 with diethyl malonate. Introduction of the amino group at the a-position of 4 or 6 was carried out via oximation or bromination to give the amino ester 9 or 4. Attempts to prepare DL-α-amino-1,3,4-thiadiazol-2-ylacetic acids from 9 or 4 were unsuccessful because the amino acids were decarboxylated too rapidly to be isolated in the free form.

Cadmium activities have been obtained for dilute solutions of silver in cadmium at 776 K from emf measurements using the cell: W-Cd|CdI2 + Cd (αCd = 1)||CdI2 + AgI + Cd (αCd < 1)|Cd, Ag-W. When the displacement reaction 2Ag + CdI2 ⇄ Cd + 2AgI is taken into account, the calculated cadmium activities follow the equation αCd = 1 − NAg − 0.607 N Ag 2 with a standard deviation of 0.00001 for those measurements (taken by the most precise method) used in the least squares fit. The largest deviation from the curve for all points measured was 0.0006 or 0.9 g/cal in \( {\overline G _{Cd}} \).

A novel synthesis of carbamate ester using carbon dioxide as a direct material is reported in this article. The direct reaction of carbon dioxide, aliphatic amines, and alkyl halides was found to give the corresponding alkyl carbamate esters in good yields. Reactions using secondary alkyl bromides gave carbamate esters in higher yields than those using primary or tertiary alkyl bromides. The carbamate ester yields increased with the addition of N,N-dimethylformamide to the reaction system of carbon dioxide, amines and, alkyl halides. This reaction is considered to proceed by an SN2 displacement reaction of the alkyl halide by the carbamate anion formed from the reaction of carbon dioxide and the amine.

The electronic absorption spectra of HgXY (HgCll, HgBrl, and HgBrCl) in water at 20 °C are calculated over the complete wavelength range, and shown not to be the mean of those of HgX2+ HgY2. For the reaction HgX2+ HgY2⇌ 2HgXY the spectra have been derived by two different techniques, which give the same profile. Equilibrium constants (log K), independent of added Na[ClO4], are: HgCll, 1.40 ± 0.15; HgBrl, 1.26 ± 0.10; HgBrCl, 0.70 ± 0.10. The reaction is exothermic. The replacement reaction HgX2+ Y–→ HgXY + X– has not previously been studied spectroscopically to obtain the formation constants (log K), which are 0.98 ± 0.05, 0.52 ± 0.09, and 0.23 ± 0.09, respectively. Accurate molar absorption coefficients could not be computed, but the spectral profiles are identical with the other results. The formation constants have been obtained by a new graphical method. The three independent methods have shown earlier incomplete spectra to be unreliable. Further, all the equilibrium and formation constants reported are the most accurate to date. The resolved spectral bands are discussed and assigned. The absence of the expected allowed transition 1Σ+→1Σ+(X) is explained as due to the proximity of 1Σ+(X) and 1Δ(Y) interacting by spin–orbit coupling to produce the representation 1Δ, to which transitions are forbidden.

The synthesis of (±)-cuparene (11), which includes as the key step an intramolecular carbenoid displacement reaction at the benzylic position of a benzyl sulphide derivative, is described.

Reaction of 3-chloro-6-methyW-nitropyridazine 1-oxide (5) with methanolic ammonia at 0° led to a replacement of the chlorine atom by a methoxy group as well as by an amino group. Reaction of the 3-methoxy-6-methyl-4-nitropyridazine 1-oxide (6) with the same reagent led to amino-demethoxylation; this replacement reaction was very slow. Attempts to perform these reactions with liquid ammonia failed. Pmr spectroscopy of solutions of compound 6 in methanolic ammonia revealed that no σ-adduct was present. However in liquid ammonia a 1:1 σ-adduct at C-5 i.e. 12b was formed. 3,6-Dimethoxy-4-nitropyridazine 1-oxide (7) gave with methanolic ammonia an amino-demethoxylation at C-6. No σ-adduct could be detected by pmr spectroscopy. However, in liquid ammonia convincing pmr data were obtained showing the presence of a 1:1 σ-adduct at C-5.

Photoemission study of the Ga/InP(110) interface, in particular at the In 4d cooper minimum (CM) reveals that the growth of the deposited Ga on InP(110) at room temperature (RT) has two modes: chemisorption at low coverage and metallic island formation at high coverage, whereas the Ga overlayer is much more uniform at 80K low temperature (LT). A replacement reaction between Ga and InP is found to take place only underneath the Ga islands. Metal screening from the Ga islands is suggested to weaken the substrate bonds and enhance the replacement reaction. Distinct behavior of Fermi level pinning has been observed at different temperatures. This is correlated with the temperature dependence of the overlayer morphology as well as the interfacial reaction.

Treatment of the title chloro compound (9) with sodium cyanide in N,N-dimethylformamide or dimethyl sulphoxide yielded methyl 2-cyan;-2,5-dihydro-5-(5'-methoxycarbonylfurfurylmethylene)-furan-2-carboxylate (12) and methyl 2-cyano-2,5-dihydro-5-[bis(5'-methoxycarbonylfurfuryl)methylenelfuran-2-carboxylate (13) as well as methyl 5-cyanomethylfuran-2-carboxylate (8).

Segregation of Mn in Cu-Mn(5%) alloy is observed in the temperature range of 520 to 700 K. The activation enthalpy of segregation is found to be about 25 kJ/mole. Surface oxidation of Cu-Mn(5%) below and above the segregation temperature shows $Cu_2O$ formation on the surface. On vacuum annealing the oxidized alloy at 670 K, the displacement reaction $Cu_2O$+Mn \rightarrow 2Cu+ MnO occurs on the surface. The oxidation behaviour of Cu-Mn(25%) is similar to that of Cu-Mn(5%).

Cystathionine γ-synthase from Salmonella catalyzes the γ replacement reaction in which O-succinyl-l-homoserine and l-cysteine form succinic acid and cystathionine, an important intermediate in methionine biosynthesis. In the absence of l-cysteine the enzyme catalyzes a γ elimination reaction in which O-succinylhomoserine is decomposed to α-ketobutyrate, NH3 and succinic acid. β-Mercaptopropionic acid, a non-competitive inhibitor of γ elimination, has been shown to be a substrate for the γ replacement reaction. The reaction product has been identified, by mass spectroscopy, as S-carboxyethyl-l-homocysteine. A kinetic study of this γ replacement reaction has demonstrated that β-mercaptopropionic acid has no effect on the enzyme's affinity for O-succinylhomoserine. It is suggested that the γ replacement reaction with l-cysteine is kinetically similar to that with β-mercaptopropionic acid.

Publisher Summary This chapter discusses three independent syntheses of 2,6-diamino-2,6-dideoxy- d -mannose. The first synthesis utilizes the facile conversion of methyl 4,6- O -benzylidene- α - d -glucopyranoside via the allo-2,3-epoxide to the altro-derivative, which is hydrogenated, N-benzoylated, and methanesulfonylated, which suffers a neighboring group displacement reaction to the manno-oxazoline on reaction with sodium acetate in ethanol. During debenzylidenation to give 2-Phenyl-1'- O -methyl- α - d -mannopyrano-‚2',3':4,5’-Δ 2 -oxazoline, tosylation and acetylation to give 2-Phenyl-4'- O -acetyl-1'- O -methyl-6'- O - p -tolylsulfonyl- α - d -mannopyrano-‚2',3': 4,5’-Δ 2 -oxazoline and reaction with sodium azide to give 2-phenyl-4'- O -acetyl-6'-azido-6'-deoxy-l'- O -methyl- α - d -mannopyrano-‚2',3': 4,5’- Δ 2 -oxazoline, the oxazoline function remains intact. Hydrogenation and hydrolysis of 2-phenyl-4'- O -acetyl-6'-azido-6'-deoxy-l'- O -methyl- α - d -mannopyrano-‚2',3': 4,5’- Δ 2 -oxazoline gives the free amino sugar 2,6-diamino-2,6-dideoxy- β - d -mannose dihydrochloride, which can be selectively acetylated to give another compound, namely, 2,6-diacetamido-2,6-dideoxy- α - d -mannose.

Publisher Summary It is natural that the great success in the application of the chromatographic method to various separation problems in organic and biochemistry should inspire attempts to apply similar procedures for amino acids and protein breakdown products in general. On the other hand, chromatography has not yet been worked out so well in aqueous solutions as in organic solvents, and in many cases, it presents some difficulties, mainly because there is no such great variety of elution agents available. The ideal case of adsorption separation may be realized with an adsorbent combining strongly only with the substance to be separated out of a mixture and showing no or a very weak affinity for the other components. Such cases may often be realized by suitable choice of adsorbent and solvent in the case of substances soluble in organic solvents. Thus in one single operation a substance or a group of substances may be separated out of a mixture. The “elution” of amino acids and other cations from a cation exchanger with acid should be a typical displacement reaction. Measurements with the optical methods show that this is the case, if the process is carried out slowly on a finely powdered material.

The three-stranded helical complex of polyadenylic acid and polyinosinic acid, poly (A+ 2I), reacts with single-stranded polycytidylic acid to form a double-stranded helix, poly (I + C), with the release of single-stranded poly A according to the reaction, Poly (A + 2I) + 2 poly C → 2 poly (I + C) + poly A This strand displacement reaction was examined by ultraviolet and infrared spectroscopy of the reaction mixture and the reaction products were separated by sucrose gradient sedimentation and identified by ultraviolet spectroscopy. The reaction proceeds readily to completion at temperatures well below the T m of the less stable reactant helix, poly (A + 2I).

The rates of substitution reactions of trans -[Rhen2Cl2]+ are first -order in complex concentration and independent of the nature and concentration of the substituting group. They also proceed without stereochemical rearrangement (1). These reactions appear, therefore, to be free of the difficulties which complicate studies of Co(III) and Pt(IV) complexes and were accordingly chosen as suitable for systematic investigation of the trans -effect in octahedral complexes.

The reversible Li-driven copper extrusion/insertion mechanism into Cu2.33V4O11 electrode has been studied and a new ion-exchanged assisted electrochemical process was unravelled. This process, entails during the charging of “Lix V4O11 + Cu0” composite electrodes vs. Li, the oxidation of Cu metal into copper ions that concomitantly exchanged for lithium ions to produce back Cu2.33V4O11. The electrochemical performances of such cells, namely in terms of capacity retention and power rates, are explained on the basis of the electrochemically generated Cu ions that can either being ion-exchanged with Li within the Li-V-O host or released in the solution. When the former does occur we show, owing to excellent kinetic of both, the ion-exchanged reaction between Cu2+ and Li+ together with a fast charge transfer between Cu0 and Cu2+, that high rate performances electrodes can be achieved whereas when the latter prevails the cells rapidly fail. It appears then that Cu+ ions should be removed. Thus, a new copper vanadate Cu1.1V4O11 phase has been isolated by both chemical and electrochemical removal of Cu from the mother Cu2.33V4O11 phase, and its electrochemical performance in Li cells studied. The removal of copper was shown to occur in a topotactic manner resulting in a stacking of [V4O11]n layers linked by differently coordinated copper ions. This new phase reversibly reacts with 5 Li, leading to a capacity of about 260 mAh/g, through a process involving a reversible displacement reaction entailing to the growth/disappearance of Cu dendrites.

Metal-reinforced Al{sub 2}0{sub 3}-matrix composites were prepared using reactive hot pressing. The volume fraction of the reinforcing phase was controlled by the stoichiometry of the particular displacement reaction used. Dense Al{sub 2}0{sub 3}-Ni and Al{sub 2}O{sub 3}-Nb composites were fabricated using this technique. The best combination of strength, 610 MPa, and toughness, 12 MPam{sup 1/2}, was found for the Al{sub 2}O{sub 3}-Ni composites. Indentation cracks and fracture surfaces showed evidence of ductile deformation of the Ni phase. The Al{sub 2}O{sub 3}-Nb composites had high strength, but the toughness was lower than expected due to the poor bonding between the Nb and A1{sub 2}0{sub 3}phases.

Three strategies have been tested to obtain stable mesoporous CoNi@Pt nanorods with a very high effective area and good performance for methanol electro-oxidation. They are based on, firstly, an electrochemical synthesis of the CoNi nanorods using three clearly different systems (micellar solution, water-in-ionic liquid microemulsion and suspension of polystyrene nanoparticles), and, secondly, a posterior platinum shell formation by interfacial replacement reaction. The obtained nanorods have been compared with pure platinum ones prepared following the three methods. The synthesized mesoporous platinum nanorods already show very good performance for methanol oxidation in comparison with compact ones or the usual Pt/C catalyzers, but the mesoporous CoNi@Pt nanorods have demonstrated much better performance for methanol oxidation, due to the more active platinum atoms in the shell of platinum than in the bulk, the higher good poison tolerance and the lower cost of the material -owing to the drastic saving in platinum in the nanostructures-. The mesoporous CoNi@Pt nanorods obtained from the water-in-ionic liquid microemulsion are the best candidates as electrocatalysers because they provide a significantly higher mass-normalized current density (1326 mA mg −1 ), a good stability in the sulfuric acidic medium and significant electrocatalytic stability under continuous operating conditions.

A flow-injection configuration based on a closed flow system which includes a single spectrophotometric detector and allows iterative detection by passage of the reacting plug n times through the same detector is described. The information obtained can be used in the simultaneous determination of species by kinetic methods. The example given is the simultaneous determiantion of iron(III) and cobalt(II) via the EGTA/PAR ligand displacement reaction.

A novel co-continuous composite of Al 2 O 3 and Al has been developed, consisting of approximately 65% (by volume) of the ceramic phase. It is formed by a liquid phase displacement reaction, involving the displacement of Si from SiO 2 and its replacement by Al. A model for the formation mechanism is presented, based on the reaction thermodynamics and the associated experimentally determined transformation kinetics. It is shown that the process is essentially near-net shape, in which the features of the SiO 2 precursors are faithfully reproduced in the composite product. Various physical and mechanical properties that are exhibited by this composite have been determined and are presented.

The solid state reaction CsCl+Nal → CsI+NaCl was investigated, employing diffusion couples with two different contents of divalent cation impurities, in the temperature range 350-419 °C. From kinetic determinations, inert marker experiments and X-ray diffraction analysis it was possible to deduce that the rate − determining step is the diffusion of I- in CsI via VI.

Cubic ZrO2 is stabilized at room temperature by the addition of AIN. The percentage of c-ZrO2 in the mixture of c-ZrO2 and m-ZrO2 increases linearly with the addition of up to 20 mol% AIN and decreases thereafter. Stabilization becomes complete at 50 mol% AIN. The lattice spacing of the cubic phase gradually expands up to 20 mol% AIN. A displacement reaction ZrO2+ AIN → ZrN+Al2O3 occurs above 20 mol% AIN and is completed at 50 mol% AIN.

A displacement reaction with 18F-caesium fluoride (anhydrous) was employed to label 2-deoxy-2-fluoro-D-glucose.

2-(Chloromethyl)-3,4-diphenylfuran reacted with aqueous potassium cyanide to give an α-angelica lactone derivative (V, 3,4-diphenyl-5-methyl-2(5H)furanone), which has never been isolated in such a reaction, as the main product.

Replacement reaction of peptide NH with chlorine was applied to the peptide antibiotics, gramicidin S and tuberactinamine N. The rate of chlorination followed by NMR spectra demonstrates that the hydrogen-bonded peptide NH in the molecule is much more susceptible to chlorination than the solvent-exposed peptide NH.

Reaction du dimethylamino-5 thiocanne avec le chlorure de benzenesulfonyle ou l'anhydride acetique