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ABSTRACT Many states are considering, and some states have actively pursued, banning the use of perchloroethylene (PERC) in dry cleaning establishments. Proposed legislation has led many dry cleaners to consider [...]

The results of the reaction between Ba atom and HBr are studied by using the quasi-classical trajectory (QCT) calculation on extended London-Eyring-Polanyi-Sato (LEPS) potential-energy surface (PES). The vibrational distribution, reaction cross section, and rotational alignment of the product BaBr have been calculated. The calculations predict that the reaction cross section decreases, while the translation energy and rotational energy increase with the increasing of collision energy. It has been found that low collision energy favors the abstraction reaction, whereas high collision energy leads to an insertion reaction. The calculated results agree with the experimental data and some relative theoretical results as well. Key words: QCT, LEPS PES, vibrational distribution, reaction cross section, rotational alignment. On a realise une etude theorie de la reaction entre un atome de baryum et du HBr en faisant appel a des calculs de trajectoire quasi-classique (TQC) sur une surface d'energie potentielle (SEP) etendue de London-Eyring-Polanyi-Santo (LEPS). On a calcule la distribution vibrationnelle, la section droite de la reaction et l'alignement rotation du produit BaBr. Les calculs ont permis de predire que, une augmentation de l'energie de collision s'accompagne d'une diminution de la section droite de la reaction alors que l'energie de translation et l'energie de rotation augmentent. On a trouve qu'une faible energie de collision favorise une reaction d'abstraction alors qu'une energie de collision elevee conduit a une insertion. Les resultats calcules sont en bon accord avec les donnees experimentales ainsi qu'avec certains resultats theoriques. Mots-cles : trajectoire quasi-classique (TQC), LEPS SEP, distribution vibrationnelle, section droite de reaction, alignement reactionnel., [Traduit par la Redaction] Introduction Along with the interaction of experiments and theories in the field, the study of molecular reaction dynamics has obtained great development and extraordinary achievements in [...]

Several crystalline polymorphs have been discovered for picryl bromide. Among the several forces that control the formation of such polymorphs are the interactions among the nitro groups and phenyl rings of those crystals. Although there are >300 structures to be found in the Cambridge Structural Database displaying the nitro-phenyl interaction, nonetheless this interesting and apparently important, interaction, seems not to have been discussed within any of the papers reporting the structures. In this article, quantum calculations are reported that assess the strength of these nitro-phenyl interactions within a crystal of picryl bromide. The rather flat molecules of picryl bromide are arranged in layered planes within the crystal, and we examine the attractive interactions that occur within a given plane, and between adjacent planes. Calculations of Hartree Fock and Moller Plesset perturbation theory carried to a second-order expansion are used. Both quantum mechanical approximations are implemented with 6-31G* basis functions. Hartree Fock | Moller Plesset perturbation theory | quantum mechanics

ABSTRACT In an earlier paper the ozone-forming potential of n-propyl bromide (NPB) was studied with a new methodology designed to address issues associated with a marginal smog-forming compound. However, the [...]

Aryl allylic alcohols are converted to hydrogenated unsaturated ketones or allylic halides by using excess Moffatt-Swern reagent. The oxidation/halogenation reaction has performed well with both oxalyl chloride and oxalyl bromide, thus providing access to the corresponding chlorides or bromides, respectively.

The bromination of 6,7,8,9-tetrahydro-5H-5,9-ethenobenzo[a][7]annulene has yielded regio- and stereospecifically formed dibromides arising from the alkyl shift where the bromine exclusively attacks the double bond from the endo face of the double bond. The results have shown that the pyramidalization of the double bond and steric repulsion caused by the methylene protons are responsible for the stereo- and regioselective addition of bromine.

1-Arylmethyl-2-(cyanomethyl)aziridines are transformed into 4-(N,N-bis(arylmethyl)amino)-3-(pyrrolidin-1-yl)butanenitriles and 4-(N,N-bis(arylmethyl)amino)-2-butenenitriles through 4-(N,N-bis(arylmethyl)amino)-3-bromobutanenitriles in high yields. The main steps have involved the unprecedented regiospecific ring opening of intermediate 2-(cyanomethyl)aziridinium salts by bromide and pyrrolidine in acetonitrile at the substituted aziridine carbon atom.

A study was conducted to demonstrate the feasibility of immobilizing a bilayer-forming surfactant onto an ion-exchange resin with retention of gel to liquid-crystalline phase transition behavior. The results confirmed the retention of a gel to liquid-crystalline phase transition of the surfactant occurring between 296 and 318 K.

Bromo- and iodoalkenes have undergone trifluoromethylation in N,N-dimethylacetamide (DMA) with 'C[F.sub.3]Cu' generated from [(C[F.sub.3]).sub.2]Hg and Cu. Variable stereochemical inversion is seen with substrates having a gem-carbonyl group, while substrates with gem-hydrogen, -alkyl, or -alkenyl groups have provided products with stereochemical retention.

The electrosynthesis, isolation and characterization of reaction products between [C.sub.60.sup.2-] and benzyl bromide in PhCN are reinvestigated. The visible and near-infrared spectra of the monoanion and dianion of 1,2-[(PhC[H.sub.2]).sub.2][C.sub.60] are described.

An experiment was carried out by subjecting molecular clusters of B[Br.sub.3] (Boron tribromide) to electron ionization and mass analysis in a reflectron time-of flight mass spectrometer. The results have predicted that fragment ions smaller than B[Br.sub.3.sup.+] undergo reactions with neutral B[Br.sub.3] molecules to form covalently bound adduct species that function as core ions within the clusters.

The freeze/thaw procedure is used to prepare the surfactant-containing poly(vinyl alcohol) (PVA) cryogels by drying and reswelling hydrogel patches in decyltrimethylammonium ([C.sub.10]TAB) aqueous solutions. It is shown that ([C.sub.10]TAB) micellization is unperturbed by the confinement of the surfactant molecules within the polymeric network of a freeze/thaw PVA hydrogel, and there is no direct surfactant-polymer interaction taking place.

A laboratory-scale model is developed to study the mechanism involved in the horizontal transport of Escherichia coli under saturation-excess flow conditions, focusing on the potential for E. coli to attach to soil particles during transport. The results have shown that in runoff generated by saturation-excess conditions, bacteria are rapidly transported across the surface and have little opportunity to interact with the soil matrix.

The thermal decomposition of quaternary ethylammonium chloride, bromide, and iodide is studied using the experimental techniques of thermal gravimetry coupled to Fourier transform infrared spectroscopy (TG- FTIR) and differential scanning calorimetry (DSC) as well as the density functional theory (DFT) and MP2 quantum- chemical methods. The respective experimental enthalpies of dissociation of the chloride, bromide, and iodide are 158, 181 and 195 kJ/mol.

A novel strategy for screening the enzyme inhibitors from the complex mixtures by capillary electrophoresis with an on-column immobilized enzyme microreactor created by an ionic binding technique is reported. The enzyme microreactor was prepared in two steps: First, the capillary wall was dynamically coated with a polycationic electrolyte hexadimethrine bromide (HDB) by simply flushing the column using the HDB solution. Subsequently, a plug of the enzyme solution was injected and incubated for 5 min to permit the enzyme molecules to immobilize on the positively charged coating via ionic binding. To demonstrate this strategy, angiotensin-converting enzyme (ACE) was employed as a model for the enzyme immobilization, inhibition study, and inhibitor screening. It has been proved that such a prepared immobilized ACE microreactor displays a high enough activity and stability. Furthermore, the immobilized enzyme microreactor could be easily renewed. The inhibition study or inhibitor screening was accomplished through the following procedure: (i) the substrate solution was injected and incubated within the microreactor for a short time span; (ii) subsequently, the voltage was applied to separate the product of the enzyme reaction from the unreacted substrate based on their different mobilities, the peak area of the product representing the enzyme activity; (iii) a certain amount of enzyme inhibitor or candidate compound was spiked into the substrate solution to assay the reduction of the immobilized enzyme activity. Thus, the inhibitors can be easily identified if the reduced peak area of the product is observed in electropherograms. Because the injection volume of the capillary was only 9.8 nL and the enzyme could be reusable, the assay cost could be dramatically reduced. The screening of a small compound library containing natural extracts and commercially available inhibitors was performed. The present approach has proved to be simple, rapid, and robust.

The outcome of reactions of 1-bromo-4-tert-butylbenzene, a representative aryl bromide, with n-BuLi or t-BuLi at 0 degree Celsius in a variety of solvent systems is investigated. The products of reactions of 1-bromo-4-tert-butylbenzene with n-BuLi vary significantly with changes in solvent composition.

The influence of interface reactions on gas-phase molecular halogen production from pure NaCl and NaBr aerosols is examined with the help of the Model of Aerosol, Gas and Interfacial Chemistry (MAGIC 2.0). The main source of Cl2 is the interface process involving Cl-(sub surf) and OH(g).

The resonance Raman (RR) and surface--enhanced resonance Raman scattering (SERRS) of 4'-(N,N'-dimethyl-aminostyryl)-4-proplypyridinium bromide in acetonitrile solution and on a colloidal silver surface is discussed. The interaction with the silver surface is found to occur through the nitrogen lone pair of the pyridyl or the dimethylamino group of the molecule with a tilted orientation.

The 1-fluoro-1-haloalkenes undergo Pd-catalyzed Negishi cross-couplings with primary alkylzinc bromides to give multisubstituted fluoroalkenes and the alkylation was transselective giving pure Z-fluoroalkenes in most cases. The highest yields were obtained with Pd2(dba)3 and PdCl2(dppb) catalysts but the best stereochemical outcome was obtained with less reactive Pd(PPh3)4.

Nitrogen electrode reaction is studied in a LiBr-KBr-CsBr melt containing Li(sub 3)N. The results of quantitative analysis of anodically evolved gas from a LiBr-KBr-CsBr-Li(sub 3)N melt shows that the oxidation of N(super 3-) ions proceeds to produce pure nitrogen gas almost quantitatively at potentials more positive than 0.3 V versus Li(super +)/ Li and the standard formal potential of the N(sub 2)/N(super 3-) redox couple is evaluated and the thermodynamic quantities for Li(sub 3) is estimated.

The novel vanadium thiobromide, V(sub 4)S(sub 9)Br(sub 4), with a square-planner metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic property and the heat capacity, and density functional theory (DFT) calculation of the electronic structure. The electronic structure of V(sub 4)S(sub 9)Br(sub 4) is characterized by a high spin state, that is, the electronic system is in the excited state.

The kinetics of the Cr(sub aq)O(super 2+)/Br(super _) reaction in acid solution, electron transfer reactions of Cr(sub aq)O(super 2+) are presented. It is observed that the magnitude of the absorbance change at the wavelengths of 266nm and 293nm is sensitive to the concentration of Cr(sub aq)O(super 2+) and Br(super _).

The supersaturational ratio, S, was theoretically related to the supply rate of solute, Q, from growth rate and mass-balance equations in the quasi-steady state in the growth process of isotropic monodisperse particles. The results revealed that the supersaturation ratio was found out to be 1.28 as an average.

The selectivity of electrochemical nitric oxide (NO) reduction by heme-didodecyldimethylammonium bromide (DDAB) and myoglobin-DDAB films as a function of potential and pH are examined. The selectivity of the pathway depends on whether a proton or NO molecule is transferred to a Fe(super II)-NO(super -) reaction intermediate and is influenced by pH, NO concentration and potential.

A high-yielding cross-coupling reaction of unactivated alkyl bromides possessing beta-hydrogens with alkylzinc halides utilizing a Pd/N-heterocyclic carbene (NHC) catalyst at room temperature is described. An investigation of different NHC precursors reveals that the bulky 2,6-diisopropylphenyl moiety is necessary to achieve high coupling yields.

Molecular dynamics simulations are used to study the solid and liquid properties and to predict the melting point of 1-n-propy1-4-amino-1,2,4-triazolium bromide ([patr][Br]) using force field based on Canongia Lopes and coworkers. The structures of the solid and liquid phases are characterized with radial distribution functions, which show that there are strong spatial correlations among neighboring ion pairs in liquid [patr][Br].

A convenient and chemoselective formation of functionalized benzofurans containing remote bromide functionality is reported. The products are formed by a new BBr3-mediated domino 'ring-cleavage-deprotection-cyclization' reaction.

Potential energy surface based on ab initio calculations are scaled, shifted, and dilated to generate three-dimensional morphed potential for Ar-HBr that reproduces the measured value of D0. These calculations provide a basis for making a comprehensive comparison of the different morphed potentials using the methodologies applied.

1,2-Dipyridiniumditribromide-ethane is synthesized and explored as a new efficient brominating agent. The crystalline ditribromide reagent is stable for months and acts as a safe source of bromine requiring just 0.5 equiv for complete bromination.

Glyoxal bis(N-methyl-N-phenylhydrazone) and its related compounds such as 2-pyridine-carboxaldehyde N-methyl-N-phenylhydrazone were prepared and examined as ligands for the Suzuki-Miyaura cross-coupling reaction of aryl halides and arylboronic acids. It was concluded that the Suzuki-Miyaura reaction of aryl bromide and arylboronic acids can be performed under mild phosphine-free conditions, based on Pd(OAc)(sub 2)/hydrazone and its related compounds with cesium carbonate in the DMF-water system under an aerobic atmosphere at room temperature.

The mechanism of forming silica spherical particles with radially orientated mesopores is investigated. Both intermediate and final products formed during precipitation of silica and cetytrimethylammonium bromide (CTAB) from solutions of ethanol, water, and ammonia are also examined.

A theoretical study on the torquoselectivity of the electrocyclic ring opening of 2,3-disubstitutedmono and dibromo cyclopropanes was carried out at the B3LYP/6-311++G level. As a result of charge donation from the dissociating C-C bond to the antibonding orbital of the breaking C-Br bond, only one of the two allowed disrotatory paths for the disrotatory ring opening that takes place in concert with the C-Br bond cleavage, is energetically accessible, both in gas phase and in solution.

In the presence of chloride or bromide, nickel(II) and Hatu [Hatu = H2NC(=NH)NHC(=S)NH2] assemble to yield the metallacages [Ni6(atu)8X][ClO4]3 (atu = deprotonated form of Hatu; X = Cl, Br). The synthesis of the cages depended to a great extent on the nature of the anions and the solvents used.

The transient organoindium intermediates formed in the reaction of proparpyl bromide with indium in aqueous media and tetrahydrofuran is examined by NMR spectroscopy and found to be allenylindium (I) and allenylindium (III) dibromide. The results suggest that computational methods may be helpful in the understanding of these organometallic reactions in aqueous media.

The effect of the leaving group on the reaction rate and branching ration is investigated using a methodology developed for studying the product distributions of gas-phase SN2 and E2 reactions. The previous condensed phase data indicate a reactivity order of iodide > bromide > trifluoroacetate for substitution reactions, however the basicities of bromide and trifluoroacetate are reversed in the condensed phase so the reactivity pattern does not reflect the relative re action exothermicities.

Kinetics of excited-state proton-transfer reactions and proton-induced fluorescence quenching of 1-naphthol and 2-octadecyl-1-naphthol in micellar solutions of cetyltrimethylammonium bromide, polyoxyethylene(23) lauryl ether (Brij 35), and sodium dodecyl sulfate is studied by using stationary and time-resolved fluorescence techniques.

The effect of a positively charged dodecyl trimethylammonium bromide (DTAB) surfactant on the aqueous solvation of coumarin 314 (C314), a solvatochromic molecule, at the air/water interface was investigated. Steady-state and femtosecond time-resolved second harmonic generation (SHG) spectroscopy was employed as a surface-selective tool to characterize the solvation of C314.

The discovery of one-pot, three-step system involving the reaction of a range of primary amines with 2-bromoethyl-phenanthridinium bromide and leading to an unprecedented class of dihydro-imidazo-phenanthridinium (DIP) compounds, which exhibit DNA affinity and high cytotoxic activity is reported. A methodology is developed by means of a biphasic system using N-bromosuccinimide as a co-oxidizing agent and it has also been extended to other N-heterocyclic cation derivatives such as quinolinium and quinazolinium.

The synthesis of micelle-templated silicas is described. The self-assembly of inorganic silica and micelles of cetyltrimethylammonium bromide containing different amounts of 1,3,5-trimethylbenzene micelles used for this purpose is also examined.

Solvation dynamics of coumarin 480 (C480) is studied in a nanoporous sol-gel matrix. Its effect in the presence of cetyltrimethylammonium bromide is studied.

The interaction between dioctadecyldimethylammonium bromide (DODAB), chloride (DODAC), or acetate (DODAAc) cationic bilayer fragments (BF) and polystyrene sulfate (PSS) particles is examined, by means of zeta-potential, and particle diameter analysis, at and above equivalence of total surface areas for bilayers and particles (A(sub b)/A(sub p)) over a range of low NaCl and lipid concentrations.

The functionalization of carbon nanotubes with pyrene-containing dendra is investigated to examine the difference between Single-walled (SWNTs) and multiple-walled carbon nanotubes (MWNTs), and to assess the effect of the tether length. The results revealed that a significant emission contributions is from pyrene excimers in all functionalized carbon nanotubes samples in solution, and both SWNTs and MWNTs serve as efficient quenchers for the pyrene photoexcited states.

The interaction of the positively charged surfactant DDAB (didodecyldimethyl ammonium bromide) with preformed vesicles from POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine), and negatively charged surfactant oleate, are investigated. In both cases the matrix effect are shown by DDAB with the formation of mixed vesicles of size distribution depending on reactant concentrations.

Solid state solvation of HCl and HBr (HX acids) was investigated by FRIR spectroscopy, with methanol (MeOH), dimethyl ether (DME), and tetrahydrofuran (THF) acting as solvents. Effort was devoted to finding those composition ratios for which the acid and the solvent readily form mixed crystalline and amorphous solids and to the study of the extent of acid solvation in these solids.

It has been demonstrated that by strapping the calix[4]pyrrole core, substantial increases in chloride and bromide binding affinity in acetonitrile and DMSO could be achieved. The work seemed to allow the modification of the inherent anion selectivity of calix[4] pyrroles, in that the larger strapped system showed an increased affinity for bromide relative to chloride.

It has been demonstrated that Michael addition of metal ketone enolate to alpha, beta-unsaturated esters successfully proceeds using tin enolate combined with Bu4NBr-catalyst. An ab initio calculation for the reaction system clarified the details of the reaction course.

The self-assembly of heterosupramolecular system consisting of a tripodal viologen, adsorbed at the surface of a titanium dioxide nanoparticle which threads a crown ether to form a pseudorotaxane is described. The viologen, a 1,1'-disubstituted-4, 4E-bipyridinium salt with a rigid tripodal anchor group, is synthesized.

Indanones and 2-cyclopentenones are successfully prepared in good to excellent yields by the palladium-catalyzed carbonylative cyclization of unsaturated aryl iodides and dienyl triflates, iodides and bromides, respectively. A number of ketone derivatives are prepared.

The syntheses of several new simple negative, a simple positive, and multiple negative photochromes containing the dihydropyrene-cyclophanediene photochromic system are described. Electrochemical readout of the state of the switch is demonstrated for the benzo system as a potential useful alternative to optical readouts.

The opening of tartrate acetals with dialkylboron bromide is studied. The mechanism for the induction of diastereoselectivity that is derived from the opening is downstream for the ring fission.