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We present a molecular dynamics study of the liquid and plastic crystalline phases of CCl3Br. We investigated the short-range orientational order using a recently developed classification method and we found that both phases behave in a very similar way. The only differences occur at very short molecular separations, which are shown to be very rare. The rotational dynamics was explored using time correlation functions of the molecular bonds. We found that the relaxation dynamics corresponds to an isotropic diffusive mode for the liquid phase but departs from this behavior as the temperature is decreased and the system transitions into the plastic phase. [ABSTRACT FROM AUTHOR]

Using ab initio calculations, we have studied the structures, properties, and nature of halogen bonds in H2CS-XY (XY = FF, ClF, ClCl, BrF, BrCl, and BrBr) complexes. The results show that the ring-shaped complexes are formed by a halogen bond (S···X) and a secondary hydrogen bond (H···X). We also analyzed the H2CS-ClF-ClF and FCl-H2CS-ClF complexes to investigate the cooperative and diminutive halogen bonding. The cooperative effect of halogen bonding is found in the former, while the diminutive effect is present in the latter. We finally considered the solvent effect on the halogen bond in H2CS-BrCl complex and found that the solvent has a prominent enhancing effect on it. The complexes have also been analyzed with natural bond orbital, atoms in molecules, and symmetry adapted perturbation theory method. [ABSTRACT FROM AUTHOR]

This report details a photoelectron spectroscopy (PES) and theoretical investigation of electron affinities (EAs) and electronic structures of several atmospherically relevant higher bromine and iodine oxide molecules in the gas phase. PES spectra of BrO2- and IO2- were recorded at 12 K and four photon energies-355 nm/3.496 eV, 266 nm/4.661 eV, 193 nm/6.424 eV, and 157 nm/7.867 eV-while BrO3-, IO3-, and IO4- were only studied at 193 and 157 nm due to their expected high electron binding energies. Spectral features corresponding to transitions from the anionic ground state to the ground and excited states of the neutral are unraveled and resolved for each species. The EAs of these bromine and iodine oxides are experimentally determined for the first time (except for IO2) to be 2.515 ± 0.010 (BrO2), 2.575 ± 0.010 (IO2), 4.60 ± 0.05 (BrO3), 4.70 ± 0.05 (IO3), and 6.05 ± 0.05 eV (IO4). Three low-lying excited states along with their respective excitation energies are obtained for BrO2 [1.69 (A 2B2), 1.79 (B 2A1), 1.99 eV (C 2A2)], BrO3 [0.7 (A 2A2), 1.6 (B 2E), 3.1 eV (C 2E)], and IO3 [0.60 (A 2A2), 1.20 (B 2E), ∼3.0 eV (C 2E)], whereas six excited states of IO2 are determined along with their respective excitation energies of 1.63 (A 2B2), 1.73 (B 2A1), 1.83 (C 2A2), 4.23 (D 2A1), 4.63 (E 2B2), and 5.23 eV (F 2B1). Periodate (IO4-) possesses a very high electron binding energy. Only one excited state feature with 0.95 eV excitation energy is shown in the 157 nm spectrum. Accompanying theoretical calculations reveal structural changes from the anions to the neutrals, and the calculated EAs are in good agreement with experimentally determined values. Franck-Condon factors simulations nicely reproduce the observed vibrational progressions for BrO2 and IO2. The low-lying excited state information is compared with theoretical calculations and discussed with their atmospheric implications. [ABSTRACT FROM AUTHOR]

The three lowest (1A′, 2A′, and 1A′′) adiabatic potential energy surfaces (PESs) for the Br(2P) + H2 reactive system have been computed based on the multi-reference configuration interaction (MRCI) method including the Davidson's correction with a large basis set. These three adiabatic PESs have been transformed to a diabatic representation, leading to four coupling potentials. In addition, the spin-orbit matrix elements were also obtained using the Breit-Pauli Hamiltonian and the unperturbed MRCI wavefunctions in the Br + H2 channel and the transition state region. Consequently, six coupling potentials were obtained and their characteristics were extensively discussed. Nonadiabatic quantum dynamics calculations for this system have been realized with these realistic diabatic potentials instead of previous semi-empirical diabatic potentials. Based on two-state model nonadiabatic calculations for the Br(2P3/2, 2P1/2) + H2 reaction, the Br(2P1/2) + H2 reaction was found to show less reactivity than the Br(2P3/2) + H2 reaction at collision energies beyond the threshold of the Br(2P3/2) + H2 reaction. Our results are consistent with the previous studies on the XH2 (X = F, Cl) system, which indicate that the adiabatically forbidden channel is dominant at low energies in the open-shell halogen atom plus H2 reactions. [ABSTRACT FROM AUTHOR]

The out-of-phase and in-phase ladder type Br-bridged Pt complexes are investigated by time-resolved luminescence spectroscopy in pico- and femtosecond time regions. The observed luminescence spectra have peaks at 0.87 and 0.94 eV in out-of-phase and in-phase materials, respectively, and are assigned to self-trapped excitons. The wave-packet oscillations in self-trapped excitons (STE) are observed in both materials. The time-evolution curves are analyzed in terms of the secondary radiation theory of strongly coupled electron-phonon system. The period and dephasing time of oscillations as well as the lifetime and spectral shape of the STE luminescence are determined. The fast dephasing or cooling of the wave-packet motion observed in the in-phase type complex is ascribed to inter-chain interactions within the ladder. [ABSTRACT FROM AUTHOR]

The photodissociation dynamics of 3-bromo-1,1,1-trifluoro-2-propanol (BTFP) and 2-(bromomethyl) hexafluoro-2-propanol (BMHFP) have been studied at 234 nm, and the C-Br bond dissociation investigated using resonance-enhanced multiphoton ionization coupled with time-of-flight mass spectrometer (REMPI-TOFMS). Br formation is a primary process and occurs on a repulsive surface involving the C-Br bond of BTFP and BMHFP. Polarization dependent time-of-flight profiles were measured, and the translational energy distributions and recoil anisotropy parameters extracted using forward convolution fits. A strong polarization dependence of time-of-flight profiles suggest anisotropic distributions of the Br(2P3/2) and Br(2P1/2) fragments with anisotropy parameter, β, of respectively 0.5 ± 0.2 and 1.2 ± 0.2 for BTFP, and 0.4 ± 0.1 and 1.0 ± 0.3 for BMHFP. The measured velocity distributions consist of a single velocity component. The average translational energies for the Br(2P3/2) and Br(2P1/2) channels are 9.2 ± 1.0 and 7.4 ± 0.9 kcal/mol for BTFP, and 15.4 ± 1.8 and 15.1 ± 2.0 kcal/mol for BMHFP. The relative quantum yields of Br(2P3/2) and Br(2P1/2), which are 0.70 ± 0.14 and 0.30 ± 0.06 in BTFP and 0.81 ± 0.16 and 0.19 ± 0.04 in BMHFP, indicate that the yield of the former is predominant. The measured anisotropy parameters for the Br(2P3/2) and Br(2P1/2) channels suggest that the former channel has almost equal contributions from both the parallel and the perpendicular transitions, whereas the latter channel has a significant contribution from a parallel transition. Non-adiabatic curve crossing plays an important role in the C-Br bond dissociation of both BTFP and BMHFP. The estimated curve crossing probabilities suggest a greater value in BTFP, which explains a greater observed value of the relative quantum yield of Br(2P1/2) in this case. [ABSTRACT FROM AUTHOR]

The doubly positively charged gas-phase molecules BrO2+ and NBr2+ have been produced by prolonged high-current energetic oxygen (17 keV 16O-) ion surface bombardment (ion beam sputtering) of rubidium bromide (RbBr) and of ammonium bromide (NH4Br) powdered ionic salt samples, respectively, pressed into indium foil. These novel species were observed at half-integer m/z values in positive ion mass spectra for ion flight times of roughly ∼12 μs through a magnetic-sector secondary ion mass spectrometer. Here we present these experimental results and combine them with a detailed theoretical investigation using high level ab initio calculations of the ground states of BrO2+ and NBr2+, and a manifold of excited electronic states. NBr2+ and BrO2+, in their ground states, are long-lived metastable gas-phase molecules with well depths of 2.73 × 104 cm-1 (3.38 eV) and 1.62 × 104 cm-1 (2.01 eV); their fragmentation channels into two monocations lie 2.31 × 103 cm-1 (0.29 eV) and 2.14 × 104 cm-1 (2.65 eV) below the ground state minimum. The calculated lifetimes for NBr2+ (v″ < 35) and BrO2+ (v″ < 18) are large enough to be considered stable against tunneling. For NBr2+, we predicted Re = 3.051 a0 and ωe = 984 cm-1; for BrO2+, we obtained 3.033 a0 and 916 cm-1, respectively. The adiabatic double ionization energies of BrO and NBr to form metastable BrO2+ and NBr2+ are calculated to be 30.73 and 29.08 eV, respectively. The effect of spin-orbit interactions on the low-lying (Λ + S) states is also discussed. [ABSTRACT FROM AUTHOR]

The influence of the spin-Zeeman (SZ) operator in the evaluation of the spin-orbit effect on the nuclear magnetic shielding tensor in the context of the linear response within the elimination of the small component approach is critically discussed. It is shown that such term yields no contribution to the isotropic nuclear magnetic shielding constant, but it may be of great importance in the determination of individual tensor components, and particularly of the tensor anisotropy. In particular, an interesting relation between the SZ and orbital Zeeman contributions to the spin-orbit effect for the case of linear molecules is shown to hold. Numerical examples for the BrH, IH, and XeF2 molecules are presented which show that, provided the SZ term is taken into account, results of the individual shielding tensor components and the tensor anisotropy are in good agreement with those obtained by other theoretical methods, and particularly by the Dirac-Hartree-Fock approach. [ABSTRACT FROM AUTHOR]

The gas-phase infrared spectra of bromodifluoromethane, CHBrF2, have been examined at medium resolution in the range of 200–9500 cm-1. The assignment of the absorptions in terms of fundamental, overtone, combination, and hot bands, assisted by quantum chemical calculations is consistent all over the region investigated. Accurate values of integrated band intensities have also been determined for the first time in the range of 500–6000 cm-1. Structural and molecular spectroscopic properties have been calculated at high level of theory. The coupled cluster CCSD(T) method in conjunction with a hierarchical series of correlation consistent basis sets has been employed and extrapolation to complete basis set has been considered for the equilibrium geometry. Vibrational analysis based on the second order perturbation theory has been carried out with the ab initio anharmonic force constants calculated using the second order Mo\ller–Plesset perturbation as well as coupled cluster [CCSD(T)] theory. A good agreement between the computed and the experimental data also including the integrated infrared band intensities has been obtained. [ABSTRACT FROM AUTHOR]

The heat capacities of single crystals of organic ferroelectric complexes phenazine-chloranilic acid (Phz-H2ca) and phenazine-bromanilic acid (Phz-H2ba) were measured. At temperatures below those of the reported ferroelectric phase transitions, heat capacity anomalies due to successive phase transitions were found in both complexes. Excess entropies involved in the low-temperature successive phase transitions are much larger than those due to the ferroelectric phase transitions. The temperature dependence of the complex dielectric constants showed the existence of multiple dielectric relaxation modes in both complexes and their deuterated analogs (Phz-D2ca and Phz-D2ba). We discuss the possibility of concerted hopping of neighboring protons within a hydrogen-bonded chain while taking into account the one-dimensional nature of the chain. [ABSTRACT FROM AUTHOR]

We present calculated dissociative attachment cross sections for ClCN and BrCN in the 0–20 eV energy range. In this energy region, both Cl-/Br- and CN- fragments are possible and are produced via dissociation along repulsive resonance curves. Electron scattering calculations, using the complex Kohn variational method and molecular structure calculations, were used to determine the three-dimensional surfaces and resonance parameters. The nuclear dynamics was studied in one, two, and three dimensions using time-dependent wave packet methods, employing the multiconfiguration time-dependent Hartree method for multiple dimensions. The calculated cross sections are reported and compared to the available experiments. Couplings between resonance states will also be examined and discussed. [ABSTRACT FROM AUTHOR]

Hyperpolarized 129Xe (xenon) gas dissolved in a perfluorooctyl bromide (PFOB) emulsion stabilized with egg yolk phospholipid (EYP) is a possible contrast agent for quantitative blood flow measurements using magnetic resonance imaging. The NMR line shape of xenon dissolved in PFOB emulsion depends strongly on the exchange of spins between PFOB and water. The exchange in this system depends on three factors: the geometrical factors (i.e., droplet size and surrounding water volume), the permeability of the EYP monolayer surrounding the droplet, and the diffusion coefficients of xenon in the two media. A theoretical model which predicts the line shape of xenon in the emulsion based on the Bloch-Torrey equations is presented. Fitting the full width at half maximum (FWHM) of the theoretical line shapes with the FWHM of the experimental spectra obtained from emulsions with different water dilutions allows estimation of the volume-weighted average diameter of the PFOB droplets (3.5±0.8) μm and the permeability of the EYP membrane surrounding the droplet (58±14) μm/s. [ABSTRACT FROM AUTHOR]

In this work, theoretical computations for the ground and excited states of BrOOBr have been performed at high-level ab initio molecular orbital theories. The ground-state geometries of BrOOBr in different forms (trans, cis, and twist form) have been optimized at the couple-cluster CCSD(T) level of theory with cc-pVTZ and aug-cc-pVTZ basis sets, which indicates that at CCSD(T)/cc-pVTZ level of theory, the twist form is 4.96 kcal/mol more stable than the trans form and 10.67 kcal/mol more stable than the cis form; at the CCSD(T)/aug-cc-pVTZ basis set the twist form is 4.33 kcal/mol more stable than the trans form and 9.54 kcal/mol more stable than the cis form. The vertical excitation energies and potential-energy curves for the singlet and triplet low-lying excited states of BrOOBr were calculated at both the complete active space self-consistent-field (CASSCF) level of theory and the multireference internally contracted configuration interaction (MRCI) level of theory. The differences of potential-energy curves at CASSCF and MRCI levels of theory are found for the BrOOBr excited states. At CASSCF level of theory, none of the BrOOBr excited states are bound. However, at MRCI level of theory, all the BrOOBr states studied in this work are bound or slightly bound at the Frank-Condon region. In addition, the scalar relativistic effect and the spin-orbital coupling effect on the vertical excitation energies of the electronic states of BrOOBr were estimated. [ABSTRACT FROM AUTHOR]

We have studied the photodissociation dynamics of expansion-cooled BrO radical both above (278–281.5 nm) and below (355 nm) the A 2Π3/2 state threshold using velocity map ion imaging. A recently developed late-mixing flash pyrolytic reactor source was utilized to generate an intense BrO radical molecular beam. The relative electronic product branching ratios at 355 nm and from 278 to 281.5 nm were determined. We have investigated the excited state dynamics based on both the product branching and the photofragment angular distributions. We find that above the O(1D2) threshold the contribution of the direct excitation to states other than the A 2Π3/2 state and the role of curve crossing is considerably larger in BrO compared to that observed for ClO, in agreement with recent theoretical studies. The measurement of low velocity photofragments resulting from photodissociation just above the O(1D2) threshold provides an accurate and direct determination of the A 2Π3/2 state dissociation threshold of 35418±35 cm-1, leading to a ground state bond energy of D00(BrO)=55.9±0.1 kcal/mol. [ABSTRACT FROM AUTHOR]

The photodissociation dynamics of vinyl bromide and perfluorovinyl bromide have been investigated at 234 nm using a photofragment ion imaging technique coupled with a state-selective [2+1] resonance-enhanced multiphoton ionization scheme. The nascent Br atoms stem from the primary C–Br bond dissociation leading to the formation of C2H3(X) and Br(2Pj;j=1/2,3/2). The obtained translational energy distributions have been well fitted by a single Boltzmann and three Gaussian functions. Boltzmann component has not been observed in the perfluorovinyl bromide. The repulsive 3A′(n,σ*) state has been considered as the origin of the highest Gaussian components. Middle translational energy components with Gaussian shapes are produced from the 1A″(π,σ*) and/or 3A″(π,σ*) which are very close in energy. Low-energy Gaussian components are produced via predissociation from the 3A′(π,π*) state. The assignments have also been supported by the recoil anisotropy corresponding to the individual components. It is suggested that intersystem crossing from the triplet states to the ground state has been attributed to the Boltzmann component and the fluorination reduces the probability of this electronic relaxation process. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ionization of bromomethanes (CH3Br, CH2Br2, and CHBr3) upon collision with metastable He*(2 3S) atoms has been studied by means of collision-energy-resolved Penning ionization electron spectroscopy. Lone-pair (nBr) orbitals of Br4p characters have larger ionization cross sections than σC-Br orbitals. The collision-energy dependence of the partial ionization cross sections shows that the interaction potential between the molecule and the He*(2 3S) atom is highly anisotropic around CH3Br or CH2Br2, while isotropic attractive interactions are found for CHBr3. Bands observed at electron energies of ∼2 eV in the He*(2 3S) Penning ionization electron spectra (PIES) of CH2Br2 and CHBr3 have no counterpart in ultraviolet (He I) photoionization spectra and theoretical (third-order algebraic diagrammatic construction) one-electron and shake-up ionization spectra. Energy analysis of the processes involved demonstrates that these bands and further bands overlapping with σC-Br or πCH2 levels are related to autoionization of dissociating (He+-Br-) pairs. Similarly, a band at an electron energy of ∼1 eV in the He*(2 3S) PIES spectra of CH3Br has been ascribed to autoionizing Br** atoms released by dissociation of (unidentified) excited states of the target molecule. A further autoionization (S) band can be discerned at ∼1 eV below the lone-pair nBr bands in the He*(2 3S) PIES spectrum of CHBr3. This band has been ascribed to the decay of autoionizing Rydberg states of the target molecule (M**) into vibrationally excited states of the molecular ion. It was found that for this transition, the interaction potential that prevails in the entrance channel is merely attractive. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The dissociative photoionization of CH[sub 2]Br[sub 2] in a region ∼10–24 eV was investigated with photoionization mass spectroscopy using a synchrotron radiation source. An adiabatic ionization energy of 10.25 eV determined for CH[sub 2]Br[sub 2] agrees satisfactorily with predictions of 10.26 and 10.25 eV with G2 and G3 methods, respectively. Observed major fragment ions CH[sub 2]Br[sup +], CHBr[sup +], and CBr[sup +] show appearance energies at 11.22, 12.59, and 15.42 eV, respectively; minor fragment ions CHBr[sub 2][sup +], Br[sup +], and CH[sub 2][sup +] appear at 12.64, 15.31, and 16.80 eV, respectively. Energies for formation of observed fragment ions and their neutral counterparts upon ionization of CH[sub 2]Br[sub 2] are computed with G2 and G3 methods. Dissociative photoionization channels associated with six observed fragment ions are proposed based on comparison of determined appearance energies and predicted energies. An upper limit of ΔH[sub f,298][sup 0](CHBr[sup +])≤300.7±1.5 kcal mol[sup -1] is derived experimentally; the adiabatic ionization energy of CHBr is thus derived to be ≤9.17±0.23 eV. Literature values for ΔH[sub f,298][sup 0](CBr[sup +])=362.5 kcal mol[sup -1] and ionization energy of 10.43 eV for CBr are revised to be less than 332 kcal mol-1 and 9.11 eV, respectively. Also based on a new experimental ionization energy, ΔH[sub f,298][sup 0](CH[sub 2]Br[sub 2][sup +]) is revised to be 236.4±1.5 kcal mol-1. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Vibrational spectrum of vinyl bromide cation in the ground electronic state was obtained by one-photon mass-analyzed threshold ionization (MATI) spectroscopy using coherent vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. From MATI spectrum, ionization energy to the ground state of the cation was determined to be 9.8171±0.0006 eV (79 180±5 cm-1). Almost complete vibrational assignments for the peaks in the MATI spectrum were possible by utilizing vibrational frequencies and Franck–Condon factors calculated at the Becke three parameter Lee–Yang–Parr (B3LYP)/6-311++G(df,pd) level. Franck–Condon analysis for one-photon MATI spectra is especially useful because calculations of only the ground electronic states are involved while that for two-photon MATI spectra requires excited state calculations. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The gas phase vibrational spectroscopy of BrHBr[sup -], a prototypical strongly hydrogen-bonded species, has been studied between 6 and 17 μm (590 and 1670 cm[sup -1]) by infrared vibrational predissociation of the BrHBr[sup -] · Ar ion. Infrared excitation was accomplished using the output of the free electron laser for infrared experiments (FELIX). Predissociation spectra were recorded by monitoring depletion of mass-selected BrHBr[sup -] · Ar ions as a function of excitation wavelength. Four prominent absorption bands are observed at 733,890, 1048, and 1201 cm[sup -1]. They are assigned to the fundamental of the hydrogenic stretching mode υ[sub 3] and a sequence of υ[sub 3] + nυ[sub 1] combinations (n = 1-3). Additional features to the blue of these bands spaced by ∼21 cm[sup -1] are attributed to combination bands involving motion of the Ar messenger atom. Differences in the relative intensities of the υ[sub 3] + nυ[sub 1] combinations bands in comparison to previous matrix experiments are rationalized on the basis of the underlying dissociation dynamics. [ABSTRACT FROM AUTHOR]

The pathways for the reaction between methylperoxy (CH[sub 3]O[sub 2]) and bromine monoxide (BrO) radicals have been examined by using the quadratic configuration interaction method. It is found that the most feasible pathway of the CH[sub 3] O[sub 2] + BrO reaction is the formation of CH[sub 3]OOOBr as an intermediate during the reaction and its dissociation into CH[sub 2]O and HOOBr. This study finds that besides CH[sub 3]OOOBr, CH[sub 3]OOBrO may also exist as an intermediate complex during the CH[sub 3]O[sub 2] + BrO reaction. [ABSTRACT FROM AUTHOR]

Despite the widespread success of transition-metal-catalysed cross-coupling methodologies, considerable limitations still exist in reactions at sp.sup.3-hybridized carbon atoms, with most approaches relying on prefunctionalized alkylmetal or bromide coupling partners.sup.1,2. Although the use of native functional groups (for example, carboxylic acids, alkenes and alcohols) has improved the overall efficiency of such transformations by expanding the range of potential feedstocks.sup.3-5, the direct functionalization of carbon-hydrogen (C-H) bonds--the most abundant moiety in organic molecules--represents a more ideal approach to molecular construction. In recent years, an impressive range of reactions that form C(sp.sup.3)-heteroatom bonds from strong C-H bonds has been reported.sup.6,7. Additionally, valuable technologies have been developed for the formation of carbon-carbon bonds from the corresponding C(sp.sup.3)-H bonds via substrate-directed transition-metal C-H insertion.sup.8, undirected C-H insertion by captodative rhodium carbenoid complexes.sup.9, or hydrogen atom transfer from weak, hydridic C-H bonds by electrophilic open-shell species.sup.10-14. Despite these advances, a mild and general platform for the coupling of strong, neutral C(sp.sup.3)-H bonds with aryl electrophiles has not been realized. Here we describe a protocol for the direct C(sp.sup.3) arylation of a diverse set of aliphatic, C-H bond-containing organic frameworks through the combination of light-driven, polyoxometalate-facilitated hydrogen atom transfer and nickel catalysis. This dual-catalytic manifold enables the generation of carbon-centred radicals from strong, neutral C-H bonds, which thereafter act as nucleophiles in nickel-mediated cross-coupling with aryl bromides to afford C(sp.sup.3)-C(sp.sup.2) cross-coupled products. This technology enables unprecedented, single-step access to a broad array of complex, medicinally relevant molecules directly from natural products and chemical feedstocks through functionalization at sites that are unreactive under traditional methods.Direct coupling of aliphatic C-H nucleophiles to aryl electrophiles is described, through the combination of light-driven polyoxometalate hydrogen atom transfer and nickel catalysis., Author(s): Ian B. Perry [sup.1] , Thomas F. Brewer [sup.1] , Patrick J. Sarver [sup.1] , Danielle M. Schultz [sup.2] , Daniel A. DiRocco [sup.2] , David W. C. MacMillan [...]

The degradation rate constant of CH3Br in the North Pacific Ocean was measured in surface seawater between September and October 1999, using a stable isotope (13CH3Br) incubation technique. Total degradation rate constants ranged from 0.02 to 0.43 d−1, decreasing in colder waters as a result of the temperature-dependence of chemical losses. Biological rate constants ranged from 0.01 to 0.20 d−1. In subtropical waters (13-20°N), biological loss rate constants were small compared to chemical loss rate constants. North of Hawaii, biological processes played an increasingly significant role in CH3Br degradation. In subpolar waters (40-58°N), biological losses dominated the removal of methyl bromide. Comparison of the measured loss rate constants with surface water CH3Br concentrations suggest that the CH3Br production rate is higher in warm, low latitude waters than in cold subpolar waters at this time of year. Diel studies revealed a midday maximum in biological degradation of methyl bromide.

Uses a retarding field technique to obtain the unimolecular kinetic energy release distribution (KERD) for a carbon-hydrogen-bromine compound dissociation. Technique for obtaining the KERD by dissociative photoionization using the helium, neon and argon resonance lines; Revelations of the highly fluxional character of the hydrogen-carbon ion.

Examines the structural and energetic properties of organic bromine compounds using the singles and doubles coupled-cluster method that includes a perturbational estimation of effects of connected triples excitation. Molecular geometry; Vibrational frequencies; Relative energetics.

Studies the combined reaction and vapor-liquid equilibrium of Br[sub 2]+Cl[sub 2]+BrCl system using the reaction ensemble Monte Carlo. Modeling of the substances as nonpolar and dipolar two-site Lennard-Jones molecules with Lorentz-Berthelot mixing rules for unlike atoms; Calculation of the complete phase compositions.

The integrated-absorption coefficients of several hyperfine lines of the magnetic dipole allowed transition of the bromine atom, Br, center at 3685.2 cm[SUP-1] were measured, and a value for the square of the magnetic dipole transition moment of the Br atom was determined. A theoretical calculation for the magnetic dipole transition moment was also carried out using a relativistic ab initio atomic structure formulation. The theoretical value was in excellent agreement with the value predicted assuming pure LS coupling, and in reasonable agreement with experiment. The Br atom was generated in equal concentration with the cyano radical (CN) by the 193 nm photolysis of cyanogen bromine, BrCN. The CN radicals were titrated by the rapid reaction with C[SUB3]H[SUB8] to generate HCN and a small amount of HNC. Both time-resolved and frequency-scanned infrared absorption spectroscopy were used to monitor the Br, HCN, and HNC species. The photolysis of BrCN at 193 nm produced both the ground state Br([SUP2]P[SUB3/2]) and the spin-orbit excited Br([SUP2]P[SUB1/2]) atoms, and the yield for the production of Br([SUP2]P[SUB1/2]) atoms was measured to be 0.31_+ 0.01. The rate constants for the quenching of Br([SUP2]P[SUB1/2]) by BrCN and C[SUB3]H[SUB8] at 293 K were also determined. [ABSTRACT FROM AUTHOR]

Investigates the electron affinity and ionization potential of bromine oxide. Application of the singles and doubles coupled-cluster method with a perturbational correction for connected triple excitations (CCSD(T)); Extrapolation of the CCSD(T)/atomic natural orbital (ANO); Reliability of CCSD(T)/ANO calculations.

Abstract Halonitrobenzenes are highly harmful to human health and the environment. Among them, chloronitrobenzenes have been reported to be degraded by several bacterial strains. However, till date, the biodegradation of bromonitrobenzenes has not been reported for any pure bacterial culture. In this study, 2-bromonitrobenzene was found to be utilized by the 2-chloronitrobenzene utilizer Pseudomonas stutzeri ZWLR2-1 as the sole source of carbon, nitrogen and energy for growth, with nitrite release. The nitroaromatic dioxygenase CnbAaAbAcAd from strain ZWLR2-1 converted 2-bromonitrobenzene to 3-bromocatechol with concomitant nitrite release. CnbC exhibited 3-bromocatechol 1,2-dioxygenase activity. The identity of 3-bromocatechol was confirmed by Liquid Chromatograph-Mass Spectrometer (LC-MS), in comparison with authentic 3-bromocatechol. These results demonstrated that the cnb cluster of Pseudomonas stutzeri ZWLR2-1 is responsible for the biodegradation of both 2-chloronitrobenzene and 2-bromonitrobenzene, providing yet another example of a bacterium having rapidly evolved a pathway to utilize multiple xenobiotics. Highlights • Pseudomonas stutzeri ZWLR2-1 grows on 2-bromonitrobenzene. • CnbAaAbAcAd converts 2-bromonitrobenzene to 3-bromocatechol. • CnbC exhibited 1,2-dioxygenase activity against 3-bromocatechol. [ABSTRACT FROM AUTHOR]

It is well‐known that boron‐doped graphene (BDG) is a promising electrode material for various applications owing to its outstanding properties, such as high electrocatalytic activity, electrical conductivity, large surface area, and cycle stability. In the present study, BDG is synthesized and used as an electrocatalyst for improving the bromine reversibility in Zn−Br2 redox flow battery applications. BDG showed a highly improved peak separation potential (145 mV) for the 2Br−/Br2 redox reaction compared to reduced graphene oxide (264 mV). Furthermore, the flow cell showed a low potential drop of 265 mV for the BDG‐based cell, which is lower than those of the other flow cells tested herein (for CF: 434 mV; r‐GO: 363 mV). The synthesized materials were also subjected to various physicochemical characterizations such as X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The durability of the flow‐cell system employing BDG/CF was analyzed at 20 mA/cm2 and the cell showed a maximum Coulombic efficiency of 86 % at the 100th cycle. Improved overall performance of a flow cell is achieved thanks to the high electrical conductivity and electrocatalytic behavior of boron‐doped graphene, which enhances the 2Br−/Br2 reaction kinetics. [ABSTRACT FROM AUTHOR]

The main aim of the present work was to study history matching of surfactant flooding using CMG-STARS simulator and experimental results. In the experimental case, the critical micellar concentration of dodecyltrimethylammonium bromide solution is obtained, and the changes in the contact angle are investigated from 1 to 10% weight. Then, after water flooding, surfactant flooding is applied on the critical micellar concentration of dodecyltrimethylammonium bromide. In the simulation case, after history matching of production data, the performance of alkaline-surfactant-polymer flooding using sodium hydroxide, hydrolyzed polyacrylamide, and that surfactant was a prediction. The numerical simulation alkaline-surfactant-polymer flooding increased the oil recovery factor 26% more than surfactant flooding. [ABSTRACT FROM AUTHOR]

New bismuth(III) bromine compounds of the heterocyclic thioamides were prepared and structurally characterized. The reaction of heterocyclic thioamides with bismuth(III) bromide resulted in the formation of the {[BiBr2(μ2-Br)(MMI)2]2·CH3COCH3·H2O} (1), {[BiBr2(MBZIM)4]·Br·2H2O} (2), {[BiBr2(μ2-Br)(tHPMT)2]2·CH3CN} (3), {[BiBr2(μ2-Br)(PYT)2]2·CH3CN} (4) and {[BiBr2(μ2-Br)(MBZT)2]2 2CH3OH} (5) complexes (MMI: 2-mercapto-1-methylimidazole, MBZIM: 2-mercaptobenzimidazole, tHPMT: 2-mercapto-3,4,5,6-tetrahydro-pyrimidine, PYT: 2-mercaptopyridine and MBZT: 2-mercaptobenzothiazole). The complexes 1–5 were characterized by melting point (m.p.), elemental analysis (e.a.), molar conductivity, Fourier-transform infrared (FT-IR), Fourier-transform Raman (FT-Raman), nuclear magnetic resonance (1H and 13CNMR) spectroscopy, UV-Vis spectroscopy and thermogravimetric-differential thermal analysis (TG-DTA). The molecular structures of 1–5 were determined by single-crystal X-ray diffraction. Complex 2 is a first ionic monomuclear octahedral bismuth(III) bromide, while the complexes 1, 3–5 are the first examples of dinuclear bismuth(III) bromide derivatives. Complexes 1–5 were evaluated in terms of their in vitro cytotoxic activity against human adenocarcinoma breast (MCF-7) and cervix (HeLa) cells. The toxicity on normal human fetal lung fibroblast cells (MRC-5) was also evaluated. Moreover, the complexes 1–5 and free heterocyclic thioamide ligands were studied upon the catalytic peroxidation of the linoleic acid by the enzyme lipoxygenase (LOX). [ABSTRACT FROM AUTHOR]

Abstract A new cationic surfactant named (N-(3-(dimethyl hexadecyl ammonio)propyl) palmitamide bromide has been evaluated as corrosion inhibitor for API N80 Steel Pipelines in 1M HCl solution. Four different techniques have been utilized for studying the corrosion behavior of the synthesized cationic amphipathic corrosion inhibitor. The prepared corrosion inhibitor was evaluated at five different temperatures 25, 30, 40, 50 and 60 °C, using weight loss technique. The three other techniques which are potentiodynamic polarization, Electrochemical impedance (EIS) and Electrochemical frequency modulation (EFM) were used for evaluation at room temperature (25 °C ± 1). The results outlined that the synthesized DMHPP amphipathic corrosion inhibitor was good inhibitor and their inhibition efficiencies were directly proportional with both the inhibitor concentration and temperature. Polarization curve revealed that the studied inhibitor act as a mixed-type of inhibitor. The adsorption of the used inhibitor led to a reduction in the double layer capacitance and an increase in the charge transfer resistance. The adsorption behavior of the amphipathic inhibitor obey Langmuir adsorption model. The change in free energy of adsorption of the synthesized inhibitor range from −40.5 to −45.5 kJ mol−1 as an indication for chemisorption process between inhibitor and steel. A clear correlation was found between corrosion inhibition efficiency and theoretical parameters obtained using density functional theory (DFT). [ABSTRACT FROM AUTHOR]

Abstract Photolysis of α-bromopropiophenones in acetonitrile results in formation of β-bromopropiophenones with good product selectivity, which can be coined as 1,2-Br shift reaction. The product selectivity increases when the reaction is done in neat or solid state, where only the 1,2-Br shift product is formed in some cases. The reaction is suggested to proceed by C Br bond homolysis to give a radical pair, followed by disproportionation and conjugate addition of HBr to the α,β-unsaturated ketone intermediate. When the unsaturated intermediate is stabilized by an extra conjugation, the reaction stops at the stage, in which the unsaturated ketone becomes a major product. The synthetic method described in this research fits in a category of eco-friendly organic synthesis nicely since the reaction does not use volatile organic solvents and any other additives such as acid, base or metal catalysts, etc. Besides, the method fits into perfect atom economy, which does not give any side products. The synthetic method should find much advantage over other alternative methods to obtain β-bromo carbonyl compounds. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

A new homogeneous bromine(−I/I) redox catalysis is described, which is based on monomeric bromine(I) compounds containing transferable phthalimidato groups. These catalysts enable intermolecular C−H amination reactions at previously unaccessible aliphatic positions and thus enlarge the synthetic potential of direct C−N bond formation, including its application in the synthesis of alkaloid building blocks. This aspect is demonstrated by a new synthetic approach to aspidospermidine. In addition to the development of the catalyst system, the structures of the involved bromine(I) key catalysts were fully elucidated, including by X‐ray analyses. New cat. on the block: C−H amination can be conveniently accomplished within a unique Br(−I/I) catalyst system, which opens versatile access to the synthesis of alkaloid building blocks. [ABSTRACT FROM AUTHOR]

Disinfection byproducts (DBPs) formed during potable water treatment can be affected by bromide (Br)‐containing discharges into receiving streams from coal‐fired power plants as well as other sources that increase the bromide content of the source water. This research focused on two aspects related to bromide increases in receiving streams. First, a bromide river transport model was adapted to track bromide concentrations in the river following a point discharge. In this work, the point discharges modeled were coal‐fired power plants. The model tracked the bromide concentrations at river segments after the point of discharge daily and, therefore, at water intakes as a function of time. In this article, the application of the model is illustrated for two rivers: the Ohio River along the Indiana and Kentucky borders and the Dan River in Virginia and North Carolina. Second, models to predict DBP formation due to increased bromide in source waters were developed. The source waters used in the DBP models were obtained from 13 states across the United States. Good model fits were found for predicting trihalomethane as bromide varies, as well as for predicting the unregulated sum of four haloacetic acids (HAA4). A method was also developed to predict the sum of nine HAAs (HAA9) based on measured sum of five HAAs (HAA5; the currently regulated HAAs) and modeled HAA4. The DBP formation models developed using the specific criteria evaluated in this research would have applications beyond only bromide discharges from coal‐fired power plants and would apply to any cause of a bromide increase in the source water. [ABSTRACT FROM AUTHOR]