Xn:Harmful;
75-62-7Relevant articles and documents
Kinetics of the Reaction of CCl3 + Br2 and Thermochemistry of CCl3 Radical and Cation
Hudgens, Jeffrey W.,Johnson, Russell D.,Timonen, R. S.,Seetula, J. A.,Gutman, D.
, p. 4400 - 4405 (1991)
The rate constant of the CCl3 + Br2 -> CCl3Br + Br reaction was determined as a function of temperature between 300 and 532 K and fit to an Arrhenius expression: k1 (L mol-1 s-1) = (1.8 +/- 0.4) x 108 exp-1/RT>.The reaction was studied in a tubular flow reactor by using laser photolysis to produce the CCl3 reactant and photoionization mass spectrometry to monitor CCl3 in time-resolved experiments.Previously published kinetic data were reevaluated to obtain k-1, the rate constant for the reverse reaction, and recent spectroscopic data were used to calculate accurate entropies and heat capacities.The values of k-1, k1, and these calculated thermodynamic properties were used in a third law determination to obtain ΔH0f,298.15(CCl3) = 17.0 +/- 0.6 kcal mol-1 and ΔH0f,0(CCl3) = 16.7 +/- 0.6 kcal mol-1.This information was combined with spectroscopic data on CCl3+ to obtain ΔH0f,298.15(CCl3+) = 205.2 +/- 0.6 kcal mol-1 and ΔH0f,0(CCl3+) = 203.7 +/- 0.6 kcal mol-1.Bond energies of several relevant compounds and tables of thermodynamic functions for CCl3 and CCl3+ are presented.An improved heat of formation for the CCl3O2 radical, ΔH0f,298.15(CCl3O2) = 2.7 +/- 1.1 kcal mol-1, is also reported.
Translational Energy Dependence of Gas-Phase Reactions of Halides with Halogenated Alkanes
Hop, C. E. C. A.,McMahon, T. B.
, p. 10582 - 10586 (1991)
The gas-phase bimolecular nucleophilic substitution reactions Br- + CCl4 -> BrCCl3 + Cl-, Br- + CF2Cl2 -> BrCF2Cl + Cl-, and Cl- + CBr4 -> ClCBr3 + Br- were studied as a function of the center-of-mass energy with Fourier transform ion cyclotron resonance spectrometry.From the energy dependence and the threshold energies of these reactions, conclusions were drawn concerning the mechanism involved.
PROCESS FOR PREPARING BROMOTRICHLOROMETHANE
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Page/Page column 5-6, (2018/10/19)
The present invention relates to a process for preparing bromotrichloromethane comprising a) providing bromine in chloroform; and b) radiation of the resulting solution with light in the range of 350 to 550 nm, wherein said solution of bromine in chloroform is not radiated with radiation of a wavelength below 350nm.
MANUFACTURING METHOD OF TETRAHALOMETHANE
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Paragraph 0036; 0037; 0039-0054, (2018/05/15)
PROBLEM TO BE SOLVED: To provide a method capable of manufacturing tetrahalomethane at high efficiency. SOLUTION: There is provided a method for manufacturing tetrahalomethane by bromination of trihalomethane selected from trichloromethane or tribromomethane, including mixing the trihalomethane, bromine, sodium hypochlorite, sodium hydroxide, and water to brominate the trihalomethane. It is preferable to mix trihalomethane of 0.1 to 10 mol, sodium hypochlorite of 0.1 to 10 mol, sodium hydroxide of 0.1 to 20 mol, and water of 1 to 50 mol, with respect to bromine of 1 mol. SELECTED DRAWING: None COPYRIGHT: (C)2018,JPO&INPIT
High-Pressure Studies of Radical-Solvent Molecule Interactions in the CCl3 and Bromine Combination Reactions of CCl3
Oum, Kawon,Luther, Klaus,Troe, Juergen
, p. 2690 - 2699 (2007/10/03)
The combination reactions CCl3 + CCl3 (+ M) → C2Cl6 (+ M) and CCl3 + Br (+ M) → CCl 3Br (+ M) (with rate constants of k1 and k2, respectively) were studied at temperatures of 250 and 300 K over the pressure range of 0.01-1000 bar. Helium, argon, xenon, N2, CO2, and SF6 were used as bath gases. CCl3 radicals were generated via the photolysis of CCl3Br at 248 nm, and their absorption was monitored at 223.5 nm. The limiting "high-pressure" rate constants within the energy-transfer mechanism were determined, independent of density and the choice of the bath gas, over the pressure range of 1-10 bar, to be k 1,∞(T) = (1.0 ± 0.2) × 10-11 (T/300 K)-0.17 cm3 molecule-1 s-1 and k2,∞(T) = (2.0 ± 0.2) × 10-11 (T/300 K)-0.13 cm3 molecule-1 s-1. In the helium, N, and argon bath gases, at pressures above ～40 bar, the reactions became increasingly faster when the pressure was further raised until they finally started to slow at densities where diffusion-controlled kinetics dominates. This is the first detailed report of such a peculiar density dependence of combination rate constants for larger radicals with five or eight atoms. Possible origins of these pressure effects, such as the influence of the radical-complex mechanism and the density dependence of electronic quenching, are discussed.
Chemistry of the biosynthesis of halogenated methanes: C1-organohalogens as pre-industrial chemical stressors in the environment?
Urhahn, Thorsten,Ballschmiter, Karlheinz
, p. 1017 - 1032 (2007/10/03)
We have chemical evidence that in the biosynthesis of the halomethanes C1H(4-n),X(n) (n = 1-4) three different pathways of biogenic formation have to be distinguished. The formation of methyl chloride, methyl bromide, and methyl iodide, respectively, has to be considered as a methylation of the respective halide ions. The dihalo- and trihalomethanes are formed via the haloform and/or via the sulfo-haloform reaction. The possible formation of tetrahalomethanes may involve a radical mechanism. Methionine methyl sulfonium chloride used as substrate in the incubation together with chloroperoxidase (CPO) and H2O2 gave high yields of monohalomethanes only. We were able to show that next to the CPO/H2O2 driven haloform reaction of carbonyl activated methyl groups also methyl-sulphur compounds - e.g. dimethylsulfoxide, dimethylsulfone, and the sulphur amino acid methionine - can act as precursors for the biosynthesis of di- and trihalogenated methanes. Moreover, there is some but not yet very conclusive evidence for an enzymatic production of tetrahalogenated methanes. In our experiments with chloroperoxidase involving amino acids and complex natural peptide based substrates, dihalogenated acetonitriles and several other volatile halogenated but yet unidentified compounds were formed. On the basis of these experiments we like to suggest that biosynthesis of halogenated nitriles occurs in general and therefore a natural atmospheric background should exist for halogenated acetonitriles and halogenated acetaldehydes, respectively.
Facile halogen exchange reactions: Chloroform with bromoform and carbon tetrachloride with carbon tetrabromide
Orvik, Jon A.
, p. 4933 - 4936 (2007/10/03)
Both of the title systems undergo rapid halogen exchange (half-life ca. 1-2 min) in N-methylpyrolidinone with catalytic sodium hydroxide at room temperature. Yet they differ markedly in response to added p-dinitrobenzene. The rate of the haloform exchange is unaffected, whereas the rate of the carbon tetrahalide exchange is severely retarded. The known base-induced halogen exchange reaction between chloroform and bromoform is shown not to proceed through a reversible carbene intermediate as claimed in the literature. It appears to be best described in terms of the so-called RARP mechanism (radical anion-radical pair). The mechanism proposed for the rapid exchange between carbon tetrachloride and carbon tetrabromide is initial electron transfer, halide ion loss, and ensuing radical chain scrambling of halogen atoms. The acronym RARC, standing for radical anion-radical chain, is proposed.
Fluoride anion catalyzed halogen dance in polyhalomethanes
Sasson, Y.,Kitson, F.,Webster, O, W.
, p. 599 - 600 (2007/10/02)
Tetrabutylammonium fluoride catalyzes the exchange of halogens between tetrahalomethanes.The presence of small amounts of haloform is suspected to be a necessary co-catalyst.Key Words: tetrabutyl ammonium fluoride; tetrahalomethanes; halogen exchange in.
REACTIONS OF BrCl WITH ALKYL RADICALS.
Skell, P. S.,Baxter, H. N.,Tanko, J. M.
, p. 5181 - 5184 (2007/10/02)
It is demonstrated that photohalogenation of low reactivity substrates with BrCl occurs mainly with Cl. selectivity.With tertiary or benzylic hydrogens in the substrate, mainly Br. selectivity is observed.These observations are rationalized, taking into account the relative concentrations of halogen atoms and their respective rates of hydrogen abstractions.The resultant radicals react with BrCl to make (RBr/RCl) in ratios between 1 and 15.
Reexamination of the Reaction of a "Graded Set" of Radicals with N-Bromosuccinimide: A Kinetic Argument Concerning the ? and ? States of Succinimidyl
Tanner, Dennis D.,Meintzer, Christian P.
, p. 6584 - 6589 (2007/10/02)
The NBS brominations of methylene chloride with added substrates which yield stable radicals were reinvestigated.The proposal that these substrates would affect the ratio of β-bromopropionyl isocyanate (BPI)/bromodichloromethane, the solvent bromination product, was not substantiated.Bromination of 2,3-dimethylbutane, cyclohexene, and butadiene by NBS in CH2Cl2 plus vinylidene chloride gives essentially the same BPI/CHCl2Br ratios as in the presence of neopentane but large yields of brominated and polybrominated products.Similar reactions in the presence of up to 2.5 M benzene always yield BPI but also highly brominated benzene derivatives.BPI is detected in the NBS bromination of chloroform under all conditions and is the major product in the presence of vinylidene chloride.Photolysis of N-iodosuccinimide-I2 in CHCl3 gives β-iodopropionyl isocyanate as the chief product.None of these observations support the hypothesis of ? and ? states of the succinimidyl radical, while the NBS results appear consistent with competing S.-Br. chains.
