10035-10-6

The cycloneophylplatinum(II) complexes [Pt(CH2CMe2C6H4)(κ2-NN′-2-C5H4NCH2-NH-R], R = 2-C6H4OH, 1; R = 3-C6H4OH, 2; R = 4-C6H4OH, 3, and [Pt(CH2CMe2C6H4)(κ2-NN′-2-C5H4NCH=N-2-C6H4OH)], 4, are reported. The structures of 1 and 4 each contain an intramolecular OH··Pt hydrogen bond, while complex 3 contains an intermolecular OH··Pt hydrogen bond and forms a new type of supramolecular polymer. In contrast, the complex [PtCl2(κ2-NN′-2-C5H4NCH=N-2-C6H4OH)], 5, forms a dimer through intermolecular OH··ClPt hydrogen bonding. Reaction of complex 4 with HCl or HBr occurs by oxidative addition to give hydridoplatinum(IV) complexes [PtHX(CH2CMe2C6H4)(κ2-NN′-2-C5H4NCH=N-2-C6H4OH)], 6, X = Cl; 7, X = Br. The sequential formation of isomers of these compounds is interpreted in terms of a proposed reaction mechanism.

The room-temperature ionic liquid (RT-IL) [C(CH3) 3]+ [Al2Br7]- (m.p. 2 °C) was generated by bromide abstraction from tert-butyl bromide with the Lewis acid aluminum bromide in the absence of solvent. The crystal structure of the tert-butyl cation salt was determined by X-ray diffraction. NMR, IR, and Raman spectroscopy, as well as quantum-chemical and thermodynamic calculations, confirm the composition of this RT-IL. Thus, one may consider this RT-IL to be a readily accessible (and on a large scale) cationic Bronsted acid (protonated isobutene) with the potential for further reactivity. Based on the new absolute Bronsted acidity scale, we calculated an absolute pH abs value of 171 for liquid bulk [C(CH3)3] + [Al2Br7]-. This value is about as acidic as 100 % sulfuric acid (pHabs=171) and, thus, on the edge of superacidity.

The reaction of atomic hydrogen with adsorbed Br is compared on Si(100) and Si(111) surfaces from 50 deg C to 300 deg C.On both surfaces, Br removal rate is first order in atomic hydrogen flux, first-order in Br coverage, and exhibits a near zero activation energy.On Si(111), this rate also depends on surface hydrogen coverage, indicating that different mechanisms occur on these surfaces.

Efficient gas-phase bromination of 1, 1, 1, 2-tetrafluoroethane (HFC-134a) for the preparation of 1, 1-dibromo-1, 2, 2, 2-tetrafluoroethane (CF3CFBr2) has been described for the first time. A wide-ranging experimental investigation o

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The charge- and atom-transfer reactions between Br+, HBr +, and DBr+ ions and HBr and DBr molecules have been studied in a HBr + DBr + He free jet. The ionic reactants in specific internal states were prepared by resonance multiphoton ionization of either HBr or DBr, and the ionic products were analyzed by mass spectrometry. A set of eight energetically possible reactions was considered in each case, including ions born in near-resonant ionization and photodissociation processes. Kinetic equations were integrated numerically over the appropriate reaction time and an optimization problem was solved to determine rate coefficients fit to final fractions of all ions measured in an experiment. Analytical expressions for the final fractions also were obtained and were used to derive the rate coefficients more accurately. The work is an example of a multireaction study without direct observation of all the reaction products.

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The rate constants for the reactions of H + Br2 and D + Br2 were measured by employing a pulse radiolysis-resonance absorption technique.The rate constants could be expressed by the following Arrhenius equations between 214 and 295 K: k(H + Br2) = 6.7 x 10-10 exp( - 680/T), k(D + Br2) = 6.0 x 10-10 exp( - 720/T), in units of cm3 s-1.Sudden transition state theoretical calculations were performed on the basis of modified LEPS surfaces.The calculated results were compared with the experimental ones.

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The reaction of equimolar mixtures of hydrogen and bromine diluted by inert gases was studied in the reflected shock zone over a temperature and total density range of 1400-2000 K and 1.5E-6 - 3.3E-6 mol cm-3, respectively.Infrared emission from HBr passing through a narrow inteference filter centered at 3.60 μm was recorded during observation periods typically of 500-μs duration.Conversion of the emission intensity traces to concentration-time data revealed nonlinear product growth for the low-temperature runs and near-linear product profiles at the higher temperatures.The individual experimental profiles were matched with the corresponding model calculations which employed a modern set of rate constants for the various elementary reactions comprising the atomic mechanism.The average percent deviation of 62 experiments from the calculated profiles was 5.4percent.

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A combined experimental and theoretical study of the photochemistry of CHBr3 in pure water and in acetonitrile/water mixed solvents is reported that elucidates the reactions and mechanisms responsible for the photochemical conversion of the halogen atoms in CHBr3 into three bromide ions in water solution. Ultraviolet excitation at 240 nm of CHBr 3 (9 × 10-5 M) in water resulted in almost complete conversion into 3HBr leaving groups and CO (major product) and HCOOH (minor product) molecules. Picosecond time-resolved resonance Raman (ps-TR 3) experiments and ab initio calculations indicate that the water-catalyzed O-H insertion/HBr elimination reaction of isobromoform and subsequent reactions of its products are responsible for the production of the final products observed following ultraviolet excitation of CHBr3 in water. These results have important implications for the phase-dependent behavior of polyhalomethane photochemistry and chemistry in water-solvated environments as compared to gas-phase reactions. The dissociation reaction of HBr into H+ and Br- ions is the driving force for several O-H insertion and HBr elimination reactions and allows O-H and C-H bonds to be cleaved more easily than in the absence of water molecules. This water-catalysis by solvation of a leaving group and its dissociation into ions (e.g., H+ and Br- in the examples investigated here) may occur for a wide range of chemical reactions taking place in water-solvated environments.

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The kinetics of the reactions Cl(2PJ) + SiH4 (1) and Br(2PJ) + SiH4 (2) have been investigated by time-resolved atomic resonance fluorescence spectroscopy.Halogen atoms were generated by flash photolysis of CCl4

A discharge flow system employing simultaneous, direct detection of HO2 and Br using laser magnetic resonance and resonance fluorescence, respectively, is used to study the kinetics of the title reactions.Over the temperature range 260 to 390 K, decays of

We report the rate coefficient for the reaction OH + BrO → Products (1) at 298 K to be k1(298 K) = (4.5 ± 1.8) × 10-11 cm3 molecule-1 s-1. Reaction 1 was studied in an excess of BrO, generated in a flow tube, and measured via its UV-vis absorption. OH, produced by laser photolysis, was monitored by laserinduced fluorescence. Quoted uncertainties include estimated uncertainties in the BrO concentration and that due to the unavoidable concurrent reaction of OH with Br2. Our measured value of k1 is compared with that previously reported by Bogan et al.

This FTIR study focuses on solid-state chemistry associated with formation and interconversion of the ionic HX (X = Cl, Br) hydrates. Kinetic data are reported for conversions of ice nanocrystal arrays exposed to the saturation pressure of the acids in the 110-125 K range. The product is amorphous acid dihydrate in the case of HBr, and amorphous monohydrate for HCl. The rate-determining step is identified as HX diffusion through the hydrate product crust toward the interfacial reaction zone, rather than diffusion through ice, as commonly believed. Slowing of the conversion process is thus observed with increasing thickness of the crust. The diffusion coefficient (De) and activation energy values for HX diffusion through the hydrates were evaluated with the help of the shrinking-core model. Hydrate crystallization occurs as a separate step, upon heating above 130 K. Subsequently, rates of reversible transitions between crystal di- and monohydrates were observed upon exposure to acid vapor and acid evacuation. In conversion from di- to monohydrate, the rate slows after fast formation of several layers; subsequently, diffusion through the product crust appears to be the rate-controlling step. The activation energy for HBr diffusion through crystal dihydrate is found to be significantly higher than that for the amorphous analogue. Conjecture is offered for a molecular mechanism of HX transport through the crystal hydrate, based on (i) spectroscopic/computational evidence for the presence of molecular HX bonded to X- in each of the ionic hydrate phases and (ii) the relative E a values found for HBr and HCl diffusion. Monte Carlo modeling suggests acid transport to the reaction zone along boundaries between nanocrystallites generated by multiple hydrate nucleation events at the particle surfaces. The reverse conversion, of crystalline monohydrate particles to the dihydrate phase, as well as dihydrate to trihydrate, displays nearly constant rate throughout the particle conversion; suggesting desorption of HX from the particle surface as the rate-limiting factor. Like for D e, the activation energies for desorption were found to be a??20% greater for HCl than HBr for related hydrate phases. ? 2005 American Chemical Society.

Vapor pressure as a function of temperature above solid and liquid (BrBNH)3 and the thermody-namic parameters of (BrBNH)3 sublimation and vaporization have been determined using static tensimetry with membrane null-manometer. The thermal decomposition of tribromoborazine has been studied in the saturated and unsaturated vapor regions. Irreversible decomposition occurred at noticeable rates at temperatures higher than 343 K and was accompanied by HBr evolution. In the unsaturated vapor region, thermal decomposition has far lower rates than in the saturated vapor region because of diffusion limitations. The activation energy of condensed-phase thermal decomposition of B,B',B''-tribromoborazine is 65 ± 3 kJ/mol, and this value proves that tribromoborazine decomposition at low temperatures is not accompanied by opening of the boron-nitrogen cycle.

Two methods for obtaining bromine and lithium bromide from highly mineralized brines enriched with lithium- and bromine-containing compounds, with Li:Br atomic ratio of 0.4-0.8, were studied. These methods are based on a combination of the technique for production of bromine and sorption recovery of lithium from brines to give eluates, LiCl solutions.

In situ observation of single oxidation/halogenation events by catalytically generated hypobromite species using single molecule fluorescence microscopy allows monitoring of the diffusion behavior of these halonium species from the catalyst into the bulk solution. The fluororgenic probe specifically reacts with hypohalites, yielding fluorescein that can be detected with single molecule sensitivity. It was found for two investigated catalysts (Curvularia verruculosa enzymes and tungstate-exchanged LDH crystals) that in steady-state conditions hypobromite is able to diffuse over 800 nm in the bulk solution before it oxidizes organic substrates. Copyright

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The invention discloses a preparation method of 4 - (2 - bromoethyl) phenol, which adopts relatively easily available cheap tyrosol and hydrobromic acid as a raw material, utilizes a bromination reaction of a bromine atom replacement alcohol hydroxyl group, and belongs to a substitution halogenation reaction of a classical organic reaction. The method has the technical effects of no polyhalogenation, high product purity, high yield and the like. The cheap and easily-manufactured hydrobromic acid is a brominating agent, and the reaction balance can be pushed to the direction of the generated product by proper excess use. The product yield can reach above 96%, the purity can reach 97.5% or more, the reaction liquid can be recycled after being subjected to distillation and concentration treatment, and a very good technical effect is obtained.

Hybrid lead halide perovskites have emerged as promising active materials for photovoltaic cells. Although superb efficiencies have been achieved, it is widely recognized that long-term stability is a key challenge intimately determining the future development of perovskite-based photovoltaic technology. Herein, we present reversible and irreversible photodecomposition reactions of methylammonium lead iodide (MAPbI3). Simulated sunlight irradiation and temperature (40-80 °C) corresponding to solar cell working conditions lead to three degradation pathways: (1) CH3NH2 + HI (identified as the reversible path), (2) NH3 + CH3I (the irreversible or detrimental path), and (3) a reversible Pb(0) + I2(g) photodecomposition reaction. If only the reversible reactions (1) and (3) take place and reaction (2) can be avoided, encapsulated MAPbI3 can be regenerated during the off-illumination timeframe. Therefore, to further improve operational stability in hybrid perovskite solar cells, detailed understanding of how to mitigate photodegradation and thermal degradation processes is necessary. First, encapsulation of the device is necessary not only to avoid contact of the perovskite with ambient air, but also to prevent leakage of volatile products released from the perovskite. Second, careful selection of the organic cations in the compositional formula of the perovskite is necessary to avoid irreversible reactions. Third, selective contacts must be as chemically inert as possible toward the volatile released products. Finally, hybrid halide perovskite materials are speculated to undergo a dynamic formation and decomposition process; this can gradually decrease the crystalline grain size of the perovskite with time; therefore, efforts to deposit highly crystalline perovskites with large crystal sizes may fail to increase the long-term stability of photovoltaic devices.

Four hybrid 1,1′-(1,n-alkanediyl)bis(4-methylpyridinium) bromobismuthates, namely (PiC2)2Bi2Br10 (1), PiC4(H5O2)BiBr6·2H2O (2), (PiC5)2Bi2Br10 (3) and (PiC6)2(H5O2)Bi2Br11 (4), were prepared by a facile solution method. The crystal structures of 1 and 3 contain zero-dimensional Bi2Br10 anion units. A 2-D network structure consisting of {H5O2}[BiBr6]·2H2O interconnected by hydrogen bonds was found in 2 and a 1-D network structure consisting of {H5O2}[Bi2Br11] was observed in 4.

Novel benzothiadiazole-based second-order nonlinear optical (NLO) chromophores with different push-pull structures were developed. Incorporation of benzothiadiazole (BTD) as a bridge for improving the electro-optic (EO) coefficient (r33) of bulky materials has not been well investigated, despite its extensive application in other photonic materials as electron acceptor. NMR and MS have been used to characterize the structure of synthesized chromophores 5-7. Optical properties have been investigated by UV-vis spectra. Density functional theory calculations have been used to calculate the first-order hyperpolarizability (β) of chromophores r1, 5a, 7a and 5b. Moreover, the poling results of guest-host EO polymers, 5a/PC and 5b/PC, afforded good r33 values of 67 pm V-1 and 45 pm V-1, respectively. All the results demonstrated an improvement in both micro- and macroscopic nonlinearity after incorporation of BTD into chromophores.

The invention provides a method for producing by-product hydrobromic acid in synthesis of bromobenzene. Under the condition of reflowing temperature, by virtue of a separation tower and a total condenser, the bromine vapor volatilized into the tower is continuously eluted by the benzene under the condition of reflowing, so that the aim of improving the comprehensive utilization rate of bromine and the quality of the by-product hydrobromic acid is realized. The method provided by the invention comprises the following specific steps of: 1) adding benzene and a catalyst in a reactor, at the temperature of warming and reflowing, dropping bromine, and obtaining the bromobenzene by debenzolizing and refining the synthesized liquid; and 2) continuously eluting the end gas synthesized in the step 1) by the benzene in the tower, cooling the end gas in a fractional condenser, and conveying the cooled gas in an end gas absorption system. The content of the free benzene in the by-product hydrobromic acid obtained by the method is less than 40PPM, and the by-product hydrobromic acid is a colorless or slightly yellow transparent liquid, and has no various change in appearance after being stored for more than one year.

The "element effect" in nucleophilic aromatic substitution reactions (SNAr) is characterized by the leaving group order, L = F > NO2 > Cl ≈ Br > I, in activated aryl substrates. A different leaving group order is observed in the subs

This invention concerns a promoted catalyst system for making one or more alkanols from synthesis gas. The catalyst system contains a ruthenium compound and a halogen promoter dispersed in a low-melting tetraorganophosphonium salt. The halogen promoter is a compound capable of generating HX (where X═Cl, Br, or I) under reaction conditions. The invention also concerns a process for selectively preparing one or more alkanols from synthesis gas using the promoted catalyst system.

The present invention relates to macrocyclic compounds of Formula (I) that are useful as inhibitors of the hepatitis C virus (HCV) NS3 protease, their synthesis, and their use for treating or preventing HCV infections.

Described are a particular group of novel aromatic hydrocarbon telomers that, on bromination, result in the formation of novel flame retardants having a uniquely beneficial combination of properties. The resultant flame retardants and uses thereof are als

The invention includes a method of preparing hypochlorite-activated solutions of hypobromous acid and/or hypobromite ion. The method includes the steps of mixing a solution of a source of bromide ion with a solution of a source of hypochlorite ion to activate the bromide ion, allowing sufficient time to maximize the activation of the bromide ion, and storing the solution before use. The invention also includes a method of using the solution to wash meat and poultry carcasses, trim, and offal to reduce pathogenic microorganisms. The solutions may also be used to reduce pathogenic microorganisms in industrial cooling water and on food contact hard surfaces and equipment. The solutions may be stored for up to about three hours before use and are stable for that period of time.

The invention relates to substituted azaindole derivatives, to methods for the production thereof, to medicaments containing said compounds and to the use of substituted azaindole derivatives for producing medicaments.

The protonation of the dinuclear phosphinito bridged complex [(PHCy 2)Pt(μ-PCy2){κ2P,O-μ-P(O)Cy 2}Pt(PHCy2)] (Pt-Pt) (1) by Bronsted acids affords hydrido bridged Pt-Pt species the structure of which depends on the nature and on the amount of the acid used. The addition of 1 equiv of HX (X = Cl, Br, I) gives products of formal protonation of the Pt-Pt bond of formula syn-[(PHCy2)(X)Pt(μ-PCy2)(μ-H)Pt(PHCy 2){κP-P(O)Cy2}] (Pt-Pt) (5, X = Cl; 6, X = Br; 8, X = I), containing a Pt-X bond and a dangling κP-P(O)Cy2 ligand. Uptake of a second equivalent of HX results in the protonation of the P(O)Cy2 ligand with formation of the complexes [(PHCy 2)(X)Pt(μ-PCy2)(μ-H)Pt(PHCy2){κP- P(OH)Cy2}]X (Pt-Pt) (3, X = Cl; 4, X = Br; 9, X = I). Each step of protonation is reversible, thus reactions of 3, 4, with NaOH give, first, the corresponding neutral complexes 5, 6, and then the parent compound 1. While the complexes 3 and 4 are indefinitely stable, the iodine analogue 9 transforms into anti-[(PHCy2)(I)Pt(μ-PCy2)(μ-H)Pt(PHCy 2)(I)] (Pt-Pt) (7) deriving from substitution of an iodo group for the P(OH)Cy2 ligand. Complexes 3 and 4 are isomorphous crystallizing in the triclinic space group P1 and show an intramolecular hydrogen bond and an interaction between the halide counteranion and the POH hydrogen. The occurrence of such an interaction also in solution was ascertained for 3 by 35Cl NMR. Multinuclear NMR spectroscopy (including 31P-1H HOESY) and density-functional theory calculations indicate that the mechanism of the reaction starts with a prior protonation of the oxygen with formation of an intermediate (12) endowed with a six membered Pt1-X ... H-O-P-Pt2 ring that evolves into thermodynamically stable products featuring the hydride ligand bridging the Pt atoms. Energy profiles calculated for the various steps of the reaction between 1 and HCl showed very low barriers for the proton transfer and the subsequent rearrangement to 12, while a barrier of 29 kcal mol-1 was found for the transformation of 12 into 5.

The reaction of the closo-dodecaborate anion with hydrogen halides in dichloroethane is studied. Regardless of the hydrogen halide used (HCl, HBr, HI), the chlorination process with the formation of monoand disubstituted products is the main in all cases. The substitution has a weakly pronounced stepwise character. The synthesized compounds are identified by IR spectroscopy, 11B NMR, and ESI mass spectrometry. The structure of a single crystal of the complex Ni(Bipy)3(B12H 10.668Cl1.332) ? 3CH2CN ? 0.464H 2O is determined by X-ray diffraction analysis. Nauka/Interperiodica 2007.

The reactions of the closo-decaborate anion with hydrogen halides and dichloroethane have been studied. Irrespective of the hydrogen halide used (HCl, HBr, HI), chlorination to give mono-, di-, and trihalosubstituted products is the major process. The product ratio depends on the hydrogen halide used and on the synthesis temperature and time. The products have been identified by 11B NMR, IR, and ESI mass spectra. The structure of (Ph 3(NaphCH2)P)2B10H8Cl 2 has been studied by X-ray diffraction. The geometry distortion of the closo-decaborate core found in the chlorinated derivatives is retained on further chemical transformations of the compound.

It is proposed that the solvolytic intermediate C(BMe)11 performs aromatic substitution by a novel mechanism. Copyright

The invention includes convenient methods of preparing: (1) highly concentrated liquid bromine-containing biocidal solutions, (2) highly concentrated mixed halogen liquid bromine and chlorine-containing biocidal solutions, and (3) high-activity bromine-containing biocidal solids, all having excellent physical and chemical stability. One method yields solutions that have concentrations of bromine in excess of 18% as Br2 (8% as Cl2) in which the mole ratio of hydroxide ion to hydrogen ion source is at least 1.9:1. Another method employs elemental bromine in conjunction with a solid organic or inorganic halogenating agent to yield halogen solutions at concentrations greater than 22.9% as Br2 (10.2% as Cl2). This method can be performed under conditions that exceed the solubility of the active ingredient such that it crystallizes and is recovered as a hydrated or anhydrous salt in good yield.

Liquid and solid bromine-containing compositions are described. A liquid mixed halogen composition is also described. The highly concentrated liquid compositions and the high-activity solid compositions have excellent physical and chemical stability. The compositions are effective biocides in water treatment. Methods of preparing the compositions are also disclosed. These include combining a bromine compound in the oxidation state of -1 with hydrogen peroxide and a complexing agent followed by the addition of an alkaline source. The methods may further include the use of a solid organic or solid inorganic halogenating agent, conducting a solid-liquid separation, and adding an alkaline source.

The invention concerns ligands with at least a fluorosilicone substituent of general formulae (I) and (II); a method for preparing them and their use for producing catalysts useful for olefin polymerisation

Complexes [RuX(η3-2-C3H4R)(CO)(P down curve sign P)] (X = Cl, Br; R = H, Me; P down curve sign P = dppf, dippf) (2a-d and 3a-d) have been prepared by reaction of the η 3-allylruthenium(II) derivatives [RuX(ηsup

Ammonium chloride and bromide, (NH4)Cl and (NH4)Br, act on elemental iron producing divalent iron in [Fe(NH3) 2]Cl2 and [Fe(NH3)2]Br2, respectively, as single crystals at temperatures around 450°C. Iron(III) chloride and bromide, FeCl3 and FeBr3, react with (NH 4)Cl and (NH4)Br producing the erythrosiderites (NH 4)2[Fe(NH3)Cl5] and (NH 4)2[Fe(NH3)Br5], respectively, at fairly low temperatures (350°C). At higher temperatures, 400°C, iron(III) in (NH4)2[Fe(NH3)Cl5] is reduced to iron(II) forming (NH4)FeCl3 and, further, [Fe(NH3)2]Cl2 in an ammonia atmosphere. The reaction (NH4)Br + Fe (4:1) leads at 500°C to the unexpected hitherto unknown [Fe(NH3)6]3[Fe 8Br14], a mixed-valent FeII/FeI compound. Thermal analysis under ammonia and the conditions of DTA/TG and powder X-ray diffractometry shows that, for example, FeCl2 reacts with ammonia yielding in a strongly exothermic reaction [Fe(NH3) 6]Cl2 that at higher temperatures produces [Fe(NH 3)]Cl2, FeCl2 and, finally, Fe3N.

Cyclopentadiene (CPD) is oxidized by copper(II) bromide and chloride in alcohol solutions to form dialkoxy- and haloethers and exhibits a higher reactivity than butadiene. Dialkoxy-, chloroalkoxy-, and dichlorocyclopentenes are formed from CPD and CuCl2 w

The kinetics and mechanism of the reactions OH + BrO → products (1) and OD + BrO → products (2) have been studied in the temperature ranges of 230-355 K and 230-320 K, respectively, and at total pressure of 1 Torr of helium using the discharge-flow mass s

The kinetics of the reactions of Br atoms with HO2 and DO2 radicals, Br + HO2 → HBr + O2 (1), and Br + DO2 → DBr + O2 (3), have been studied by the mass spectrometric discharge-flow method at temperatures between 230 and 355 K and at a total pressure of 1 Torr of helium. The rate coefficients measured under pseudo-first-order conditions in excess Br yield the following Arrhenius expressions: k1 = (4.9 ± 0.7) × 10-12 exp[-(310 ± 40)/T] and k3 = (1.9 ± 0.4) × 10-12 exp[-(540 ± 60)/T] cm3 molecule-1 s-1 (uncertainties are 2σ). The k3 value is measured for the first time and that of k1 is compared with those from previous studies.

Thermal decomposition of cadmium thiourea coordination compounds was considered. Cadmium sulfide is the final product for all the compounds, whereas the composition of other products of the thermolysis substantially depends on the nature of the acido ligand or the outer-sphere anion. Thermal stability parameters of the coordination compounds under study and effective activation energies of their thermolysis were determined, and a mechanism of the thermolysis was proposed.

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High-vacuum thermolyses of the intramolecularly co-ordinated gallanes Me2N(CH2)3GaX2 with X = Cl 1 or Br 2 were investigated with matrix isolation techniques. Among the products, which have been identified with

The enthalpies of solution of ZrCl4, ZrBr4, HfCl4, and HfBr4 in water and low-acidity and low-basicity solutions at 25°C are measured with an isothermal-jacket calorimeter. The standard enthalpies of formation of Zr(OH)4 and Hf(OH)4 in solution and the thermodynamic characteristics of formation of zirconium and hafnium tetrahydroxo complexes in aqueous solution are calculated.

Deprotonation of [(CO)2RReNH(CH3)CH2CH2(η 5-C5H4)]+X- (R = CO2Me, CO2Et; X = Br) followed by heating under a CO atmosphere yields the corresponding CO insertion compound (CO)2RReC(=O)N(CH3)CH2CH2(η 5-C5H4). An anologous insertion reaction proceeds more rapidly for the complexes [(CO)2XReNH(CH3)CH2CH2(η 5-C5H4)]+Y- (X = Br, I, PhS, and PhSe) in which X is a strong electron-withdrawing group. Without the presence of external ligands, the oxygen of the resultant carbamoyl group binds to the rhenium to fulfill the 18-electron rule. The η2-carbamoyl selenolate complex [(CO)PhSeRe(η2-C=O)N(CH3)CH2CH 2(η5-C5H4)] (9b) has been characterized by X-ray crystallography. Upon addition of two-electron-donor ligands, such as CO, isocyanides, and trialkyl phosphites, the n2-carbamoyl complexes convert cleanly to the corresponding η1-carbamoyl complexes.

.CBr2CO2- and .CCl2CO2- radicals, generated upon one electron reduction of tribromo- and trichloroacetic acids and .CF2CO2- radicals produced from difluoroacetic acid by reaction with .OH, exhibit optical absorptions in the UV with λmax at 290 nm (ε = 2580 dm3 mol-1 cim-1), 330 nm (ε = 3000 dm3 mol-1 cm-1) and 310 nm (ε ≈ 660 dm3 mol-1 cm-1), respectively. Mechanistically, the present report focuses on the free-radical-induced degradation of tribromoacetic acid. Absolute rate constants have been determined for the reactions of CBr3CO2- with eaq-, H., CO2. , .CH2OH, CH3.CHOH, (CH3)2.COH and .CH3 radicals to be k = 1.8 × 1010, 1.5 × 1010, 2.8 × 109, 1.6 × 109, 2.3 × 109, 3.0 × 109 and 3.0 × 107 dm3 mol-1 s-1, respectively. The major fate of .CBr2CO2- is self-termination to yield tetrabromosuccinic acid which, however, is unstable and thermally decomposes to HBr, CO2 and tribromoacrylic acid. Dibromofumaric acid, dibromomaleic acid and carbon monoxide were found as minor secondary products, formation of which is explained by a small yield of reductive decomposition of the transient tetrabromosuccinic acid. A complete and mechanistically satisfying material balance is provided for several systems in which CBr3CO2- has been degraded via a variety of radicals under various conditions. .OH Radicals do not react directly with CBr3CO2-. They have been shown, however, to contribute indirectly to the degradation of this acid via their reaction with reductively liberated bromide ions. The Br. atoms formed in this process are considered to abstract a bromine atom from CBr3CO2- or oxidize the carboxyl function in a one-electron transfer process. The formation of free Br. atoms has been recognized by pulse radiolysis through their conjugate dimer radical anions Br2.-. With respect to the other trihalogenated acids it is noteworthy that CCl3CO2- is efficiently reduced by CO2.- radicals and that CF3CO2- exhibits a high stability toward γ-irradiation and practically resists any reductive attack.

The rate constant for the HO2 + BrO reaction has been measured using the turbulent flow technique with high-pressure chemical ionization mass spectrometry for the detection of reactants and products. At room temperature and 100 Torr pressure, the rate constant (and the two standard deviation error limit) was determined to be (1.4 ± 0.3) × 10-11 cm3 molecule-1 s-1. The temperature dependence of the rate constant was investigated between 298 and 210 K, and the data was fit to the following Arrhenius expression: (2.5 ± 0.8) × 10-12 exp[(520 ±80)/T] cm3 molecule-1 s-1. Although the negative activation energy value agrees well with the current recommendation for stratospheric modeling, our absolute values for the rate constant are about a factor of 2 lower than this same recommendation.

Using the discharge flow-mass spectrometric technique, the kinetics and mechanism of the BrO+HO2 reaction have been investigated in the temperature range 233-344 K.With an excess of HO2 over BrO, the rate constant was found to be k1=(4.77+/-0.3

By removing the bromide ligand in trans- (1) by AgBF4 in the presence and absence of pyridine, pyridine-coordinated and solvent-coordinated cationic complexes, trans-BF4 (2) and trans-BF4 (3) have been obtained.These cationic phenylpalladium complexes show much greater reactivities than do the parent neutral complex 1 toward olefins to give phenylated olefins by insertion followed by β-hydrogen elimination processes.Kinetic studies concerning the insertion of methyl acrylate into the phenyl-palladium bond have indicated that the reactions are first order in the phenylpalladium complexes and that addition of pyridine to a system containing 2 and methyl acrylate inhibits the insertion reaction of the olefin.The results suggest that the generation of a cationic arylpalladium complex with a vacant site is important for the olefins to be inserted.

Time-resolved resonance fluorescence detection of Br(2P3/2) atom disappearance or appearance following 266-nm laser flash photolysis of CF2Br2/H2S/H2/N2, CF2Br2/CH3SH/H2/N2, Cl2CO/H2S/HBr/N2, and CH3SSCH3/HBr/H2/N2 mixtures has been employed to study the kinetics of the reactions Br(2P3/2) + H2S SH + HBr (1, -1) and Br(2P3/2) + CH3SH CH3S + HBr (2, -2) as a function of temperature over the range 273-431 K.Arrhenius expressions in units of 10-12 cm3 molecule-1 s-1 which describe the results are k1 = (14.2 +/- 3.4) exp, k-1 = (4.40 +/- 0.92) exp, k2 = (9.24 +/- 1.15) exp>(-386 +/- 41)/T>, and k-2 = (1.46 +/- 0.21) exp; errors are 2? and represent precision only.By examining Br(2P3/2) equilibration kinetics following 355-nm laser flash photolysis of Br2/CH3SH/H2/N2 mixtures, a 298 K rate coefficient of (1.7 +/- 0.5) x 10-10 cm3 molecule-1 s-1 has been obtained for the reaction CH3S + Br2 -> CH3SBr + Br.To our knowledge, these are the first kinetic data reported for each of the reactions studied.Measured rate coefficients, along with known rate coefficients for similar radical + H2S, CH3SH, HBr, Br2 reactions are considered in terms of possible correlations of reactivity with reaction thermochemistry and with IP-EA, the difference between the ionization potential of the electron donor and the electron affinity of the electron acceptor.Both thermochemical and charge-transfer effects appear to be important in controlling observed reactivities.Second and third law analyses of the equilibrium data for reactions 1 and 2 have been employed to obtain the following enthalpies of reaction in units of kcal mol-1: for reaction 1, ΔH298 = 364 +/- 0.43 and ΔH0 = 3.26 +/- 0.45; for reaction 2, ΔH298 = -0.14 +/- 0.28 and ΔH0 = -0.65 +/- 0.36.Combining the above enthalpies of reaction with the well-known heats of formation of Br, HBr, H2S, and CH3SH gives the following heats of formation for the RS radicals in units of kcal mol-1: ΔHfo0(SH) = 34.07 +/- 0.72, ΔHfo298(SH) = 34.18 +/- 0.68, ΔHfo0(CH3S) = 31.44 +/- 0.54, ΔHfo298(CH3S) = 29.78 +/- 0.44; errors are 2? and represent estimates of absolute accuracy.The SH heat of formation determined from our data agrees well with literature values but has reduced error limits compared to other available values.The CH3S heat of formation determined from our data is near the low end of the range of previous estimates and is 3-4 kcal mol-1 lower than values derived from recent molecular beam photofragmentation studies.

Ultraviolet irradiation (λ = 254 nm) of argon matrices containing BBr3 and high concentrations of H2 produces an intermediate, BBr2, which reacts with H2 to form HBBr2, H2BBr, and HBr. The intermediate is completely destroyed by irradiation at 680 nm, the position of a broad absorption band, producing the same hydrogenation products that form by using ultraviolet radiation. The reaction of BBr2 with HD gives HBr and DBBr2 1.6 times more readily than DBr and HBBr2. The spectrum of BBr2 has been reported earlier; herein we reassign the totally symmetric B-Br stretching mode to a weak band at 551.0 cm-1. There is no evidence that either BBr2 or BBr3 forms a ground-state complex with hydrogen in spite of the fact that BBr2 forms more readily in the presence of H2 and that it is readily converted into HBBr2 and H2BBr by H2. However, a complex of hydrogen and BBr2 in its first excited state may lead to the hydrogenation products. The yield of H2BBr is greatest when the concentration of hydrogen in the matrix is greater than about 10 mol %. Both hydrogen atoms that make up the H2BBr come from the same molecule of hydrogen. Mixtures of H2 and D2 give H2BBr and D2BBr with only a trace of HDBBr whereas matrices containing HD produce only HDBBr.

By using an appropriate coordinate system the arc length between two points on the geodesic reaction path is equal to the absolute difference between the function values (energies) belonging to the same points.This gives the possibility to avoid the tedious integration procedure necessary to get a measure of the position of the saddle point (or any other point) in the one-dimensional space of the reaction path.The method is illustrated by reaction coordinate values of transition states for a number of atom transfer reactions in comparison with those calculated by an independent method.Reaction coordinates also computed by using analytical functions are compared with those obtained by direct integration.

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The radiolysis of deoxygenated triethylsilane (Et3SiH) was studied in the presence of various concentrations of ethylbromide (EtBr) as a function of the radiation dose.Chain reactions are leading to rather high yields of Br-containing final products, e.g. using 0,93 mol/dm3 EtBr we obtained: Gi(Et3SiBr) = 138, G1(HBr) = 40, G1(Br2) = 15 and Gi(Et3Si-SiEt3) = 6, in addition to small amounts of unidentified oligomers.Based on the knowledge from previous steady-state and pulse radiolysis studies of Et3SiH, a probable reaction mechanism is postulated to allow explanation of the present results. - Keywords: Radiation Induced Br-Transfer, Ethylbromide, Triethylsilane