Recombination Of Bromine Atoms Research Articles

Flash photolysis study of the NO‐catalyzed recombination of bromine atoms

AbstractThe recombination of bromine atoms at room temperature has been studied by flash photolysis in the range of 1–100 atm of the inert diluent He, leading to a value for the third‐order rate constant of (1.5 ± 0.2) × 1015 cm6/mol2.sec. In the presence of NO the recombination is considerably accelerated. The falloff curve of the recombination Br + NO (+He) → BrNO (+He) was also measured resulting in a value for the limiting low‐pressure rate constant of (3.4 ± 1.3) × 1015 cm6/mol2.sec. In experiments with excess NO, rate constants of (2.2 ± 1) × 1014 cm3/mol·sec for the reaction Br + BrNO → Br2 + NO, and (6.1 ± 0.4) × 109 cm6/mol2.sec for the reaction Br2 + 2NO → 2BrNO were obtained.

Recombination of bromine atoms between 300 and 6000°K, theory and experiment

The dissociation of Br 2 in Ar was studied in the same shock tube using three different time dependent observables which were needed to measure the rate of the reaction: (1) Br 2 molecular absorption, (2) Br atom two-body emission and (3) density gradient change, detected by laser schlieren technique. It was found that the first observable was most useful in determination of dissociation rate constants between about 1500 and 1800°K and the second observable between about 1200 and 1700°K. Use of these two observables yielded rate constants which were in agreement with those earlier experimental data, which are likely to be most reliable. The laser schlieren technique yielded new dissociation rate constants between 2100 and 3000°K. These data were found to be consistent with the “reliable” “emission” and “absorption” data, as well as with the earlier flash photolysis data. In order to interpret the experimental results and to study the dynamics of the reaction, the dissociation of Br 2 in Ar was studied by 3-D classical trajectory calculations at 1500, 2500, 3500, and 6000°K. In agreement with earlier trajectory studies, it was found that Br 2 molecules react only if their total energy is within a few kT of dissociation limit and that metastable molecules, with total energy above the dissociation limit, are particularly reactive. The average energy, E >, and the average angular momentum, l >, transferred in dissociative and non-dissociative collisions were calculated as a function of total energy of Br 2 molecule. Generally, | E >| (non-dissoc.) and | l >| (non-dissoc.) were found to be considerably smaller than the same quantities for dissociative collisions. For energetic metastable molecules, dissociation could be accomplished by a decrease of internal energy and angular momentum of the molecule through collision. Thus, collisionally induced rotational de-excitation provides an additional mechanism for dissociation of diatomic molecules. The non-equilibrium effects in dissociation have been evaluated at 3500 and 6000°K by the method of multiple collisions. The calculated steady state dissociation rate constants between 1500 and 6000°K are in good agreement with the available experimental data. Finally, the validity of the rate quotient law, i.e. k forward / k reverse = K eg , was demonstrated by trajectory calculation technique.

Trajectory studies of atomic recombination reactions. V. Recombination of bromine atoms

Recombination of Br atoms in Ar was studied by 3D trajectory calculations between 300 and 1500°K. The recombination path via unstable Br–Ar quasidimers was included in the calculations, which yield recombination rate constants in agreement with experiment within a factor of 2, provided that the ArBr Lennard-Jones interaction is of the order of 0.5 kcal/mole.

Recombination of ground state halogen atoms. Part 4.—Kinetics of recombination of bromine atoms

The rate of recombination of Br 2P atoms at 298 K has been measured in a discharge-flow system at pressures near 300 N m–2, using absorption spectrophotometry of Br2 at λ 415 nm to measure [Br].Rate constants for the third order recombination reaction (3) are reported: Br + Br + M [graphic omitted] Br2+ M. (3), k3,M=–½[Br]–2[M]–1{d[Br]/dt}(cm6 molecule–2 s–1), 298 K: k3,Ar=(9.4 ± 2.5)× 10–33; k3,He=(2.8 ± 0.5)× 10–33; k3,Br2=(8.3 ± 3.3)× 10–32; k3,O2=(1.2 ± 0.3)× 10–32; k3,N2=(8.3 ± 3.0)× 10–33.

Nonequilibrium Effects in Atomic Recombination Reactions

Relaxation in the bromine-argon system is investigated by approximating the time evolution with a sequence of trajectory calculations. Two systems are considered: (a) recombination of bromine atoms via the radical-molecule complex mechanism and (b) rotational relaxation of a rigid rotator in a thermal bath. The phenomenological and equilibrium rate coefficients for recombination at 300°K are computed and compared. Nonequilibrium effects lead to a 19% discrepancy between the two rate coefficients after an initial transient period during which the phenomenological rate coefficient shows a distinct time dependence. Comparison of the rotational relaxation of Br2 and the rigid rotator shows the importance of vibrational-rotational coupling for highly excited molecules. The relaxation time of the vibrationally excited molecules is much greater than that of the rigid rotators.

Recombination of bromine atoms in a laminar hydrogen-bromine flame

Recombination of bromine atoms in a laminar hydrogen-bromine flame

The Photoproduction and Recombination of Bromine Atoms in the Liquid Phase

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Photoproduction and Recombination of Bromine Atoms in the Liquid PhaseRobert L. StrongCite this: J. Am. Chem. Soc. 1965, 87, 16, 3563–3567Publication Date (Print):August 1, 1965Publication History Published online1 May 2002Published inissue 1 August 1965https://doi.org/10.1021/ja01094a006RIGHTS & PERMISSIONSArticle Views56Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

HALOGEN ATOM REACTIONS: III. LUMINESCENCE FROM THE RECOMBINATION OF BROMINE ATOMS

The recombination of bromine atoms has been found to result in the emission of an orange–red glow. Analysis of the banded spectrum has resulted in the identification of the transition responsible for the visible emission as [Formula: see text] The results of a kinetic study of the glow indicate that the emission is second order in [Br] and first order in [Br2]. Several detailed preassociation mechanisms for the reaction are discussed.

Studies of the variations in bond dissociation energies of aromatic compounds. I. Mono-bromo-aryles

Investigation of the pyrolyses of bromobenzene, β -bromonaphthalene, α -bromonaphthalene, 9-bromophenanthrene and 9-bromoanthraeene in the presence of an excess of toluene has shown that reaction (1) Ar .Br → Ar • + Br (1) is the primary and rate-determining step of the pyrolysis. The progress of reaction was measured by the rate of formation of hydrogen bromide, and it was shown that this rate obeys first-order kinetics. The following values were obtained for the activation energies and frequency factors of unimolecular decompositions represented by equation (1): compound E (kcal/mole) 10 -13 v (sec -1 ) bromobenzene 70.9 2 β -bromonaphthalene 700 1.5 α -bromonaphthalene 70.9 3.5 9-bromophenanthrene 67.7 1 9-bromoanthracene 65.6 1.5 Assuming that recombination of bromine atoms with aromatic radicals does not involve any activation energy we conclude tha t the determined activation energies correspond to the respective C—Br bond dissociation energies. The effect of molecular structure on the C—Br bond dissociation energy is discussed. The heat of formation of the phenyl radical is determined, and this result is used for calculating the various Ph — X bond dissociation energies.

XXI.—The Influence of Air and Moisture on the Budde Effect in Bromine

SummaryA survey is given of recent work on the action of light on bromine vapour, both dry and in presence of air and moisture.Suggested explanations of the facts are discussed. It is concluded that the influence of water is due to a “poisoning” of the walls of the vessel, which prevents them from catalysing the recombination of bromine atoms.