Formation Of Halides Research Articles

Electrochemical specific adsorption of halides on Cu 111, 100, and 211: A Density Functional Theory study

The specific adsorption of ions onto electrode surfaces can affect electrocatalytic reactions. Density functional theory is used to investigate the specific adsorption of aqueous F−, Cl−, Br−, and I− onto Cu (111), (100), and (211) surfaces. The adsorption is increasingly favorable in the order of F− < Cl− < Br− < I−. The adsorption has a weak dependence on the surface facet, with adsorption most favorable on Cu (100) and least favorable on Cu (111). Potential ranges where specific adsorption would be expected on each facet are reported. The thermodynamics of bulk copper halide (CuX, CuX2) formation are also investigated as a function of potential. CuX formation occurs at potentials slightly more positive of halide specific adsorption and of copper oxidation in aqueous electrolytes. Specifically adsorbed halides and bulk CuX may be present during a variety of electrochemical reactions carried out over a Cu electrode in halide containing electrolyte solutions.

ChemInform Abstract: First Reusable Ligand‐Free Palladium Catalyzed C—P Bond Formation of Aryl Halides with Trialkylphosphites in Neat Water.

A reusable ligand-free palladium catalyzed phosphonation of aryl iodides, bromides and chlorides with trialkylphosphites is described for the first time in neat water. The aryl phosphonates are obtained in good to excellent yields. The reaction can be also performed with Ni(II) with longer reaction time. The role of tetrabutylammonium bromide in this reaction as reducing agent for generation of Pd(0) at room temperature is also demonstrated. Pd(0)/TBAB was easily reused for three runs without decreasing the efficiency.

Formation mechanism of nanostructured metal carbides via salt-flux synthesis.

Nanostructured metal carbides are of particular interest because of their potential as high surface area, low-cost catalysts. By taking advantage of a salt-flux synthesis method, multiple carbide compounds were synthesized at low temperatures providing a pathway to nanosized materials. To better understand the reaction mechanism, vanadium carbide (V8C7) synthesis was monitored by quenching samples at 100 °C intervals and analyzed by multiple spectroscopic methods. The reaction was determined to occur through the formation of metal halide and acetylide carbide intermediates, which were repeatedly observed by X-ray diffraction and further supported by IR and Raman spectroscopies. Control experiments were also employed to further verify this mechanism of formation by using different salt compositions and a solid-state metathesis reaction. The reaction mechanism was also verified by applying these techniques to other metal carbide systems, which produced similar intermediate compounds.

Formation of disinfection by-products in the ultraviolet/chlorine advanced oxidation process

Disinfection by-product (DBP) formation may be a concern when applying ultraviolet light and free chlorine (UV/chlorine) as an advanced oxidation process (AOP) for drinking water treatment, due to typically large chlorine doses (e.g. 5–10mgL−1 as free chlorine). A potential mitigating factor is the low chlorine contact times for this AOP treatment (e.g. seconds). Full-scale and pilot-scale test results showed minimal trihalomethane (THM) and haloacetic acid (HAA) formation during UV/chlorine treatment, while dichloroacetonitrile (DCAN) and bromochloroacetonitrile (BCAN) were produced rapidly. Adsorbable organic halide (AOX) formation was significant when applying the UV/chlorine process in water that had not been previously chlorinated, while little additional formation was observed in prechlorinated water. Chlorine photolysis led to chlorate and bromate formation, equivalent to approximately 2–17% and 0.01–0.05% of the photolyzed chlorine, respectively. No perchlorate or chlorite formation was observed. During simulated secondary disinfection of AOP-treated water, DBP formation potential for THMs, HAAs, HANs, and AOX was observed to increase approximately to the same extent as was observed for pretreatment using the more common AOP of UV combined with hydrogen peroxide (UV/H2O2).

Mechanistic insights into Brønsted acid-induced nucleophilic substitution of aliphatic imidazole carbamate with halide ions

Herein we report interesting reactivity of imidazole carbamate towards nucleophilic substitution with halide ions under Brønsted acidic conditions. Depending upon reaction conditions, halide ions could readily attack the carboxyl position and trigger decarboxylative alkyl halide formation. Alternatively, halide ions were also found to competitively undergo nucleophilic acyl substitution, which ultimately results in the generation of carbonate dimerization product.

ChemInform Abstract: Practical Access to Spiroacetal Enol Ethers via Nucleophilic Dearomatization of 2‐Furylmethylenepalladium Halides Generated by Pd‐Catalyzed Coupling of Furfural Tosylhydrazones with Aryl Halides.

Pd-catalyzed cross-coupling of furfural tosylhydrazones with aryl halides produces 2-furylmethylenepalladium halides, which can undergo intramolecular nucleophilic dearomatization to provide spiroacetal enol ethers. This is the first report on the formation of 2-furylmethylenepalladium halides from stable furfural hydrazones instead of from 2-furylmethyl halides, which are not readily accessible or are unstable.

First reusable ligand-free palladium catalyzed C–P bond formation of aryl halides with trialkylphosphites in neat water

A reusable ligand-free palladium catalyzed phosphonation of aryl iodides, bromides and chlorides with trialkylphosphites is described for the first time in neat water. The aryl phosphonates are obtained in good to excellent yields. The reaction can be also performed with Ni(II) with longer reaction time. The role of tetrabutylammonium bromide in this reaction as reducing agent for generation of Pd(0) at room temperature is also demonstrated. Pd(0)/TBAB was easily reused for three runs without decreasing the efficiency.

Molecular ordering by halide–halide interactions in dimolybdenum p-halobenzoates

A series of compounds of the form Mo2(O2C-C6H4-X)4, 1-X, and trans-Mo2(TiPB)2(O2C-C6H4-X)2, 2-X, have been prepared where X=F, Cl, Br, and I and TiPB=2,4,6-triisopropylbenzoate. The compounds 1-X (X=F, Cl) and 2-X (X=F, Cl, Br, and I) have been structurally characterized by single crystal X-ray crystallography, some of which are shown to form extended chains in the solid state due to the formation of halide–halide intermolecular interactions. Both families of compounds have been examined by electronic absorption and emission spectroscopy and the lifetimes of the singlet and triplet lifetimes have been determined. S1 lifetimes are ∼5–8ps and T1 lifetimes are ∼50–80μs. The heavy atom halogen appears to have little effect on the S1 lifetimes.

Reprint of: The enthalpy of formation of gaseous tetra-n-propylammonium cations

The standard molar enthalpies of formation of crystalline tetraalkylammonium halides, ΔfH°(R4NX,c), R=Me, Et, Pr, Bu and X=Cl, Br, I, and the corresponding lattice energies, UL(R4NX) were obtained from the literature as far as available for T=298.15K. From consistent values of these two quantities and values for ΔfH°(X−,g) the standard molar enthalpies of formation of the gaseous cations were obtained from ΔfH°(R4N+,g)=ΔfH°(R4NX,c)+UL(R4NX)+2RT°−ΔfH°(X−,g). The value for the hitherto unreported ΔfH°(Pr4N+,g)=(307±7)kJ·mol is here derived. The value for the absolute standard molar enthalpy of hydration is ΔhH°(R4N+,aq) −210kJ·mol−1, but may have an appreciable uncertainty, reflecting that of ΔfH°(R4N+,aq), obtained from interpolation of values for the Me, Et, and Bu analogues.

Practical access to spiroacetal enol ethers via nucleophilic dearomatization of 2-furylmethylenepalladium halides generated by Pd-catalyzed coupling of furfural tosylhydrazones with aryl halides.

Pd-catalyzed cross-coupling of furfural tosylhydrazones with aryl halides produces 2-furylmethylenepalladium halides, which can undergo intramolecular nucleophilic dearomatization to provide spiroacetal enol ethers. This is the first report on the formation of 2-furylmethylenepalladium halides from stable furfural hydrazones instead of from 2-furylmethyl halides, which are not readily accessible or are unstable.

The enthalpy of formation of gaseous tetra-n-propylammonium cations

The standard molar enthalpies of formation of crystalline tetraalkylammonium halides, ΔfH°(R4NX,c), R=Me, Et, Pr, Bu and X=Cl, Br, I, and the corresponding lattice energies, UL(R4NX) were obtained from the literature as far as available for T=298.15K. From consistent values of these two quantities and values for ΔfH°(X−,g) the standard molar enthalpies of formation of the gaseous cations were obtained from ΔfH°(R4N+,g)=ΔfH°(R4NX,c)+UL(R4NX)+2RT°−ΔfH°(X−,g). The value for the hitherto unreported ΔfH°(Pr4N+,g)=(307±7)kJ·mol is here derived. The value for the absolute standard molar enthalpy of hydration ΔhH°(R4N+,aq) is −210kJ·mol−1, but may have an appreciable uncertainty, reflecting that of ΔfH°(R4N+,aq), obtained from interpolation of values for the Me, Et, and Bu analogues.

Microwave-Assisted Carbohydrohalogenation of First-Row Transition-Metal Oxides (M = V, Cr, Mn, Fe, Co, Ni, Cu) with the Formation of Element Halides

The anhydrous forms of first-row transition-metal chlorides and bromides ranging from vanadium to copper were synthesized in a one-step reaction using the relatively inexpensive element oxides, carbon sources, and halogen halides as starting materials. The reactions were carried out in a microwave oven to give quantitative yields within short reaction times.

Comparative study on the photoelectrocatalytic inactivation of Escherichia coli K-12 and its mutant Escherichia coli BW25113 using TiO2 nanotubes as a photoanode

Photoelectrocatalytic (PEC) and photocatalytic (PC) inactivation of ancestor Escherichia coli K-12 and its mutant E. coli BW25113 were systematically compared using a TiO2 nanotubular photoanode. The results showed that PEC inactivation was more effective to both bacterial strains than PC process, and E. coli BW25113 showed higher resistance than E. coli K-12 in both PEC and PC systems. The findings indicate that the two strains with different genes are varied in their susceptibilities and responses to the PEC and PC treatments. The h+ was found to be the major reactive species and predominantly responsible for PEC inactivation. Scanning electron microscopy images demonstrated that the cells were severely damaged and resulted in a leakage of the intracellular components during PEC inactivation process. For a given bacterial strain, no significant effect was found on the PEC inactivation efficiency as different electrolytes were employed. However, in the presence of NaCl or NaBr, PEC inactivation efficiencies of both strains were remarkably enhanced. This phenomenon can be attributed to the efficient formation of halide and dihalide radical anions during PEC process. The different efficiencies of the two bacterial strains under same conditions can be ascribed to their different abilities to resist the inactivation of bacterial strains with different genotypes.

Catalysis by Desolvation: The Catalytic Prowess of SAM-Dependent Halide-Alkylating Enzymes

In the biological fixation of halide ions, several enzymes have been found to catalyze alkyl transfer from S-adenosylmethionine to halide ions. It proves possible to measure the rates of reaction of the trimethylsulfonium ion with I(-), Br(-), Cl(-), F(-), HO(-), and H2O in water at elevated temperatures. Comparison of the resulting second-order rate constants, extrapolated to 25 °C, with the values of k(cat)/K(m) reported for fluorinase and chlorinase indicates that these enzymes enhance the rates of alkyl halide formation by factors of 2 × 10(15)- and 1 × 10(17)-fold, respectively. These rate enhancements, achieved without the assistance of cofactors, metal ions, or general acid-base catalysis, are the largest that have been reported for an enzyme that acts on two substrates.

Light olefins synthesis from C1-C2 paraffins via oxychlorination processes

A two-step process was employed to convert methane or ethane to light olefins via the formation of an intermediate monoalkyl halide. A novel K4RuOCl10/TiO2 catalyst was tested for the oxidative chlorination of methane and ethane. The catalyst had high selectivity for methyl and ethyl chlorides, 80% and 90%, respectively. During the oxychlorination of ethane at T⩾250°C, the formation of ethylene as a reaction product along with ethyl chloride was observed. In situ Fourier transform infrared studies showed that the key intermediate for monoalkyl chloride and ethylene formation is the alkoxy group. The reaction mechanism for the oxidative chlorination of methane and ethane over the Ru-oxychloride catalyst was proposed. The novel fiber glass catalyst was also tested for the dehydrochlorination of alkyl chlorides to ethylene and propylene. Very high selectivities (up to 94%–98%) for ethylene and propylene formation as well as high stability were demonstrated.

Solar Energy Assisted Starch-Stabilized Palladium Nanoparticles and Their Application in C—C Coupling Reactions

Present work reports a novel one step, greener protocol for the synthesis of starch-stabilized palladium nanoparticles (PdNPs) with an average particle diameter of 30-40 nm. These particles were stable and uniform in size. In present protocol, the concentrated solar energy mediated reduction of palladium chloride was achieved by using citric acid as a reducing agent and starch as a capping agent. UV-Visible spectroscopy, Transmission Electron Microscopy, Field Emission Gun-Scanning Electron Microscopy, Selected Area Electron Diffraction and Electron dispersive X-ray Spectral analysis techniques were used to characterize this starch capped PdNPs. Herein; we are reporting such combination of starch and citric acid in the synthesis of PdNPs for the first time. The catalytic activity of synthesized nanoparticles has been checked for Suzuki and Heck cross coupling reactions. The product yield was confirmed by GC. The products were confirmed using GC-MS analysis and also using GC with the help of authentic standards. Solar energy assisted starch stabilized PdNPs showed excellent activity in the C-C bond formation between aryl halides (I, Br) with phenyl boronic acid and its derivatives. In addition, the catalyst showed good activity in the Heck coupling reaction of C-C bond formation of aryl halides with aromatic alkene. The use of starch, citric acid, water and solar energy makes present protocol greener.

Tribological Performance of Halogen-Free Ionic Liquids as Lubricants of Hard Coatings and Ceramics

Ionic liquids are expected to be used as new high-performance lubricants because of their low volatility, high thermal stability, and high oxidation stability. It is well known that halogen-containing ionic liquids exhibit excellent lubricity for metals. However, there is a concern about the corrosiveness of ionic liquids caused by the formation of halides. The lubricity of halogen-free ionic liquids for metals is inferior to that of halogen-containing ionic liquids; however, they do not cause any remarkable corrosion effects. In this study, the lubricity of halogen-free ionic liquids—1-butyl-3-methylimidazolium tricyanomethanide ([BMIM] [TCC]) and 1-ethyl-3-methylimidazolium dicyanamide ([EMIM] [DCN])—for hard coatings and ceramics was evaluated using an SRV oscillating sliding tester. Ionic liquids exhibited excellent lubricity for sintered ceramics. It is supposed that the lubricity of ceramics depends on the chemical interaction between the surface and the ionic liquids. Ionic liquids exhibited different lubricating properties with each nitride coating. [EMIM] [DCN] exhibited a better wear reduction than [BMIM] [TCC] on CrN, and its friction coefficient was higher than that of [BMIM] [TCC]. DLC coatings with [EMIM] [DCN] exhibited better lubricity than with [BMIM] [TCC], and the combination of H-free DLC and [EMIM] [DCN] particularly showed excellent lubricity. XPS analysis showed that two kinds of nitrogen compounds were on the sliding surface of H-free DLC lubricated with [EMIM] [DCN].

Enantioselective Synthesis of Both Enantio­mers of Chiral Allenes Using Chiral N‐Methylcamphanyl Piperazine Templates

AbstractThe reaction of unsubstitued camphanyl‐piperazine 4 with ZnCl2, phenylacetylene, and benzaldehyde in toluene gave the corresponding dipropargylamine (i.e., 15) with opposite configurations at the newly formed stereogenic centres, which, upon reaction with ZnI2 resulted in the formation of a racemic mixture of 1,3‐diphenyl allene in 45 % yield. N‐Methylcamphanyl‐piperazine regioisomer 5, prepared by selective N‐methylation of the NH moiety attached to the stereogenic centre with (S)‐configuration, upon reaction with ZnCl2, phenylacetylene, and benzaldehyde in toluene, gave the corresponding propargylamine in 90 % yield, with an (S)‐configuration at the newly formed stereogenic centre, and upon subsequent reaction with ZnI2, this intermediate gave (R)‐1,3‐diphenyl allene in 52 % yield and with 96 % ee. Reaction of N‐methylcamphanyl‐piperazine isomer 5 with several 1‐alkynes and aldehydes in the presence of ZnBr2 gave the corresponding (R)‐allenes in 40–75 % yield and 79–99 % ee. In contrast, regioisomeric N‐methylcamphanyl‐piperazine 6 reacted with ZnBr2 to give the corresponding (S)‐allenes in 38–71 % yield and with 79–99 % ee. The opposite chiral discriminating abilities of the two NH moieties in camphanyl‐piperazines was confirmed by single‐crystal X‐ray analysis of the propargylamines formed. The results are discussed considering mechanisms involving the in situ formation of alkynylzinc halides, followed by diastereoselective addition to chiral iminium ion derivatives to give the corresponding propargylamines, and subsequent conversion to chiral allenes by an intramolecular 1,5‐hydrogen shift.

Electrical Conductance and Ion Pair Formation of S-Acetylthiocholine Halides in Methanol-Water Mixtures at 25 ºC

Electrical Conductance and Ion Pair Formation of S-Acetylthiocholine Halides in Methanol-Water Mixtures at 25 ºC

BIMETALLIC Ag/Co SYNTHESIZED AT LIQUID/LIQUID INTERFACE WITH CONTROLLABLE CORE/SHELL STRUCTURES

Ultrafine Ag/Co nano-alloys have been prepared successfully using silver(I)-bis(oxalato)cobaltat(II) complex and 1,3-diaminopropane (DAP), which is a typical phase-separation system in a bulk phase diagram, in diethyl ether/aqueous solution. The product's morphology depends on the pH of the reaction solution. The use of an oxalate complex, in which two metal ions exist in one complex, is found to be effective in preventing unfavorable silver halide formation and thus is suitable for the formation of Ag/Co bimetallic nanoparticles. The crystal structure and lattice constant of the Ag/Co nano-alloys obtained were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission-electron microscopy (TEM), and UV-vis spectroscopy. These results show that DAP plays a key role in the determination of particle morphology. The results in the present study demonstrated the differences on alloying behavior between bulk and nanoscopic materials.