- Occurrence of bromoperoxidase in the marine green macro-alga, ulvella lens, and emission of volatile brominated methane by the enzyme
-
Bromoperoxidase activity was detected in the marine green macro-alga, Ulvella lens, which is used to induce the larval metamorphosis of sea urchin in aquaculture in Japan. The enzyme activity was enhanced 8.5- and 2.2-fold by the addition of cobalt and vanadium ions to the reaction mixture, respectively. The volatile halogenated compounds dibromomethane and tribromomethane were formed in the reaction mixture when the enzyme was incubated with oxaloacetate, hydrogen peroxide and potassium bromide. These results suggest that dibromomethane, which was reported to be released by U. lens and play an important role as the inducer of larval settlement and metamorphosis, is produced by bromoperoxidase in the alga.
- Ohshiro, Takashi,Nakano, Satoru,Takahashi, Yoshinori,Suzuki, Minoru,Izumi, Yoshikazu
-
-
Read Online
- Facile continuous process for gas phase halogen exchange over supported alkyl phosphonium salts
-
Chloride-bromide halogen exchange was realized when a mixture of an alkyl chloride and an alkyl bromide were reacted over a supported molten alkyl phosphonium catalyst. Conversion was found to be near equilibrium in a tubular flow reactor at 150 °C and 1500 GHSV. The catalyst was prepared by impregnation of alumina or silica support and found to be highly stable for relatively long periods of time. A pathway for the catalytic cycle is proposed.
- Sharma, Priti,Sasson, Yoel
-
p. 2824 - 2828
(2018/02/06)
-
- One-Pot Conversion of Methane to Light Olefins or Higher Hydrocarbons through H-SAPO-34-Catalyzed in Situ Halogenation
-
Methane was converted to light olefins (ethene and propene) or higher hydrocarbons in a continuous flow reactor below 375 °C over H-SAPO-34 catalyst via an in situ halogenation (chlorination/bromination) protocol. The reaction conditions can be efficiently tuned toward selective monohalogenation of methane to methyl halides or their in situ oligomerization to higher hydrocarbons. The presence of C5+ hydrocarbons in the reaction products clearly indicates that by using a properly engineered catalyst under optimized reaction conditions, hydrocarbons in the gasoline range can be produced. This approach has significant potential for feasible application in natural gas refining to gasoline and materials under moderate operational conditions.
- Batamack, Patrice T. D.,Mathew, Thomas,Prakash, G. K. Surya
-
p. 18078 - 18083
(2017/12/26)
-
- Dehalogenation of organic halides in aqueous media by hydrogen transfer from formate catalyzed by water-soluble Ru(II)-N-heterocyclic carbene complexes
-
Water-soluble [RuCl(NHC)(L)(η6-arene)] complexes (NHC?=?bmim?=?1-butyl-3-methyl-imidazole-2-ylidene;?L?=?tertiary phosphine, such as mtppms, mtppts, pta, pta-Me and pta-Bn; η6-arene?=?η6-p-cymene) were succesfully applied for the first time as catalysts in hydrodehalogenation of organic halides by hydrogen transfer from aqueous Na-formate with turnover frequencies up to TOF?=?112?h?1 at 80?°C. Simultaneous to hydrodehalogenation, aqueous formate was also decomposed to H2 and HCO3?. In case of [RuCl(bmim)(pta)(η6-p-cymene)]Cl (pta?=?1,3,5-triaza-7-phosphaadamantane) a reaction mechanism is suggested on basis of kinetic and NMR measurements which accounts for both hydrodehalogenation and formate dehydrogenation and involves [RuH(bmim)(pta)(η6-p-cymene)]+ as the key catalytic species for both cycles.
- Marozsán, Natália,Horváth, Henrietta,Erdei, Anikó,Joó, Ferenc
-
p. 103 - 109
(2016/10/09)
-
- PROCESS FOR MANUFACTURING METHYLENE BIS(THIOCYANATE)
-
This invention provides pure methylene bis(thiocyanate) in an ecor industrial process. The product is practically free of insolubles (0.1%) after prolonged storage.
- -
-
Page/Page column 14; 15
(2014/10/29)
-
- Transformation of methane to propylene: A two-step reaction route catalyzed by modified CeO2 nanocrystals and zeolites
-
Propylene from methane: The transformation of methane to propylene has been realized in a two-step route via CH3Cl or CH3Br. CeO 2 serves as an efficient and stable catalyst for the oxidative chlorination and bromination of methane to CH3Cl and CH 3Br. In the second step, a modified zeolite is highly a selective and stable catalyst for the conversion of CH3Cl or CH3Br into propylene. Copyright
- He, Jieli,Xu, Ting,Wang, Zhihui,Zhang, Qinghong,Deng, Weiping,Wang, Ye
-
supporting information; experimental part
p. 2438 - 2442
(2012/04/23)
-
- PROCESSES FOR CONVERTING GASEOUS ALKANES TO LIQUID HYDROCARBONS USING MICROCHANNEL REACTOR
-
A process for converting gaseous alkanes to olefins, higher molecular weight hydrocarbons or mixtures thereof wherein a gaseous feed containing alkanes may be thermally or catalytically reacted with a dry bromine vapor to form alkyl bromides and hydrogen bromide. Poly-brominated alkanes present in the alkyl bromides may be further reacted with methane over a suitable catalyst to form mono-brominated species. The mixture of alkyl bromides and hydrogen bromide may then be reacted over a suitable catalyst at a temperature sufficient to form olefins, higher molecular weight hydrocarbons or mixtures thereof and hydrogen bromide. Various methods and reactions are disclosed to remove the hydrogen bromide from the higher molecular weight hydrocarbons, to generate bromine from the hydrogen bromide for use in the process, to store and subsequently release bromine for use in the process, and to selectively form mono-brominated alkanes in the bromination step. One or more of the reactions of the processes of the present invention may be conducted in a microchannel reactor.
- -
-
Page/Page column 69-71
(2012/01/06)
-
- AN INTEGRATED PROCESS TO COPRODUCE AROMATIC HYDROCARBONS AND ETHYLENE AND PROPYLENE
-
An integrated process for producing aromatic hydrocarbons and ethylene and/or propylene and optionally other lower olefins from low molecular weight hydrocarbons, preferably methane, which comprises: (a) contacting at least one low molecular weight alkane, preferably methane, with a halogen, preferably bromine. under process conditions sufficient to produce a monohaloalkane, preferably monobromomethane, (b) reacting the monohaloalkane in the presence of a coupling catalyst to produce aromatic hydrocarbons and C2+ alkanes, (c) separating the aromatic hydrocarbons from the product mixture of step (b) to produce aromatic hydrocarbons, and (d) cracking at least part of the C2+ alkanes in an alkane cracking system to produce ethylene and/or propylene and optionally other lower olefins.
- -
-
Page/Page column 20
(2010/04/28)
-
- INTEGRATED PROCESS TO COPRODUCE AROMATIC HYDROCARBONS AND ETHYLENE AND PROPYLENE
-
An integrated process for producing aromatic hydrocarbons and ethylene and/or propylene and optionally other lower olefins from low molecular weight hydrocarbons, preferably methane, which comprises: (a) contacting one or more low molecular weight alkanes, preferably methane, with a halogen, preferably bromine, under process conditions sufficient to produce a monohaloalkane, preferably monobromomethane, (b) reacting a first portion of the monohaloalkane in the presence of a coupling catalyst under process conditions sufficient to produce aromatic hydrocarbons and C2-5 alkanes, (c) separating the aromatic hydrocarbons from the product mixture of step (b) to produce aromatic hydrocarbons, (d) reacting a second portion of the monohaloalkane in the presence of a coupling catalyst under process conditions sufficient to produce ethylene and/or propylene.
- -
-
Page/Page column 8
(2010/09/18)
-
- PROCESS FOR CONVERTING HYDROCARBON FEEDSTOCKS WITH ELECTROLYTIC AND PHOTOELECTROCATALYTIC RECOVERY OF HALOGENS
-
A method for converting a hydrocarbon feedstock into higher hydrocarbons is provided comprising reacting a hydrocarbon feedstock with a molecular halogen to form alkyl halides; reacting at least a portion of the alkyl halide in the presence of a catalyst to form higher hydrocarbons and a hydrogen halide; and converting at least a portion of the hydrogen halide into the molecular halogen via photoelectrocatalysis. Additional methods are also provided.
- -
-
Page/Page column 33
(2010/11/05)
-
- CONTINUOUS PROCESS FOR CONVERTING NATURAL GAS TO LIQUID HYDROCARBONS
-
A method comprising: providing a first halogen stream; providing a first alkane stream; reacting at least a portion of the first halogen stream with at least a portion of the first alkane stream in a first reaction vessel to form a first halogenated stream; providing a second alkane stream comprising C2 and higher hydrocarbons; providing a second halogen stream; and reacting at least a portion of the second halogen stream with at least a portion of the second alkane stream in a second reaction vessel to form a second halogenated stream.
- -
-
Page/Page column 66-67
(2010/04/03)
-
- CONVERSION OF METHANE INTO C3?C13 HYDROCARBONS
-
A process for converting methane into C3?C13 hydrocarbons is provided including the steps of reacting methane with oxygen and HBr/H2O over a first catalyst in a first reactor to methane bromides and converting the methane bromides into C3?C13 hydrocarbons and HBr over a second catalyst in a second reactor. The process may further include recovering HBr produced in the second reactor and recylcing it into the first reactor.
- -
-
Page/Page column 3
(2009/07/10)
-
- Thermochemical study of the liquid phase equilibrium reaction of dihalomethanes by NMR spectroscopy
-
The liquid phase equilibrium reaction of dihalomethanes (2CH2BrI ? CH2Br2 + CH2I2) has been investigated by NMR spectroscopy, as a function of the temperature and initial concentration of the reactants. The equilibrium constants have been experimentally determined for this reaction from the profile of the NMR spectra. Heat capacity measurements were carried out in the temperature range from 293.15 to 353.15 K by differential scanning calorimetry. The results relate the heats of formation of the three compounds and confirm the recently determined heat of formation of CH2I2 of 107.5 kJ mol-1.
- Dávalos,Lago,Baer, Tomas
-
p. 230 - 234
(2007/10/03)
-
- Kinetics of the transformation of halogenated aliphatic compounds by iron sulfide
-
The transformation of nine halogenated aliphatic compounds, i.e., pentachloroethane (PCA), 1,1,2,2- and 1,1,1,2-tetrachloroethanes (1122-TeCA and 1112-TeCA), 1,1,1- and 1,1,2-trichloroethanes (111-TCA and 112-TCA), 1,1- and 1,2-dichloroethanes (11-DCA and 12-DCA), carbon tetrachloride (CT), and tribromomethane (TBM), by 10 g/L FeS at pH 8.3 was investigated in batch experiments. 11-DCA, 12-DCA, and 112-TCA showed no significant transformation by FeS over ~ 120 days, but the other compounds were transformed with half-lives of hours to days. PCA and 1122-TeCA underwent dehydrohalogenation faster than FeS-mediated reductive dehalogenation reactions. The remaining compounds for which considerable transformation was observed underwent FeS-mediated reactions more rapidly than hydrolysis or dehydrohalogenation. For 1112-TeCA, the dihaloelimination product, i.e., 1,1-dichlroethylene, was the only reaction product observed. For 111-TCA, CT, and TBM, hydrogenolysis products were the only products detected, even though their mass recoveries were significantly 100%. Two simple log-linear correlations between rate constants and either one-electron reduction potentials or homolytic bond dissociation enthalpies were developed, with determination coefficients of 0.48 and 0.82, respectively. These results were consistent with a rate-limiting step involving homolytic bond dissociation. However, neither correlation precisely characterized the reactivity of all the compounds, indicating distinctions among the mechanisms for reductive dehalogenation of the compounds by FeS or the influence of additional molecular or thermodynamic parameters on rate constants.
- Hayes,Butler
-
p. 422 - 429
(2007/10/03)
-
- Catalytic reaction of methane with CBrF3
-
The catalytic reaction of CH4 with CBrF3 over Co, Cu and Mn ZSM-5 zeolites is described; major products (at low temperatures) are those expected for simple hydrodebromination: CH3Br and CHF3.
- Li, Kai,Kennedy, Eric,Dlugogorski, Bogdan,Howe, Russell
-
p. 709 - 710
(2007/10/03)
-
- Laser Pulse Photolysis of 7-Silanorbornadiene in Solution: Experimental and AM1 Studies of Complexation between Silylenes and CHBr3
-
The quantum yield (0.95 +/- 0.1) for the decomposition of 7,7-dimethyl-1,4,5,6-tetraphenyl-2,3-benzo-7-silanorbornadiene (Ib) in hexane at room temperature has been determined by the laser pulse photolysis technique.Reaction rate constants of the generated dimethylsilylene with bromoform (4.4 * 107 M-1 s-1) and Ib (5.7 * 109 M-1 s-1) have been measured.It is suggested that the reaction of Me2Si: with CHBr3 occurs via the formation of an intermediate complex (λmax = 338 nm, ε =1280 M-1 cm-1).The bimolecular rate constant for decay of the complex (2k = 1.61 * 109 M-1 s-1) has also been estimated.Semi-empirical PM3 calculations of the model reaction between the singlet SiH2 and CHBr3 show the formation at the first step of the reaction of a donor-acceptor complex stabilized by interactions between a vacant p-AO of SiH2 and a lone pair of one of the Br atoms.Such a complex should be rather stable both toward dissociation into the starting reagents (E = 23.3 kcal/mol) and further rearrangement into the insertion product, Br(H2)SiCHBr2 (E = 22.3 kcal/mol).
- Taraban, Marc B.,Plyusnin, Victor F.,Volkova, Olga S.,Grivin, Vyacheslav P.,Leshina, Tatyana V.,et al.
-
p. 14719 - 14725
(2007/10/02)
-
- Reductive dehalogenation of hexachloroethane, carbon tetrachloride, and bromoform by anthrahydroquinone disulfonate and humic acid
-
The reductive dehalogenation of hexachloroethane (C2Cl6), carbon tetrachloride (CCl4), and bromoform (CHBr3) was examined at 50 °C in aqueous solutions containing either (1) 500 μM of 2,6-anthrahydroquinone disulfonate (AHQDS), (2) 250 μM Fe2+, or (3) 250 μM HS-. The pH ranged from 4.5 to 11.5 for AHQDS solutions and was 7.2 in the Fe2+ solutions and 7.8 in the HS- solutions. The observed disappearance of C2Cl6 in the presence of AHQDS was pseudo-first-order and fit k'(CCl4) = k0[A(OH)2] + k1[A(OH)O-] + k2[A(O)22-] where A(OH)2, A(OH)O-, and A(O)22- represent the concentrations of the three forms of the AHQDS in solution. The values of k0, k1, and k2 were ~0, 0.031, and 0.24 M-1 s-1, respectively. The addition of 25 mg of C/L of humic acid or organic matter extracted from Borden aquifer solids to aqueous solutions containing 250 μM HS- or Fe2+ increased the reduction rate by factors of up to 10. The logarithms of the rate constants for the disappearance of C2Cl6 and CCl4 in seven different experimental systems were significantly correlated; log k'(CCl4) = 0.64 log k'(C2Cl4)-0.83 with r2 = 0.80. The observed trend in reaction rates of C2Cl6 > CCl4 > CHBr3 is consistent with a decreasing trend in one-electron reduction potentials. The reductive dehalogenation of hexachloroethane (C2Cl6), carbon tetrachloride (CCl4), and bromoform (CHBr3) was examined at 50°C in aqueous solutions containing either (1) 500 μM of 2,6-anthrahydroquinone disulfonate (AHQDS), (2) 250 μM Fe2+, or (3) 250 μM HS-. The pH ranged from 4.5 to 11.5 for AHQDS solutions and was 7.2 in the Fe2+ solutions and 7.8 in the HS- solutions. The observed disappearance of C2Cl6 in the presence of AHQDS was pseudo-first-order and fit k′CCl(4) = k0[A(OH)2] + k1[A(OH)O-] + k2[A(O)22-] where A(OH)2, A(OH)O-, and A(O)22- represent the concentrations of the three forms of the AHQDS in solution. The values of k0, k1, and k2 were approximately 0, 0.031, and 0.24 M-1 s-1, respectively. The addition of 25 mg of C/L of humic acid or organic matter extracted from Borden aquifer solids to aqueous solutions containing 250 μM HS- or Fe2+ increased the reduction rate by factors of up to 10. The logarithms of the rate constants for the disappearance of C2Cl6 and CCl4 in seven different experimental systems were significantly correlated; log k′CCl(4) = 0.64 log k′C(2)Cl6 approximately 0.83 with r2 = 0.80. The observed trend in reaction rates of C2Cl6 > CCl4 > CHBr3 is consistent with a decreasing trend in one-electron reduction potentials.
- Curtis,Reinhard
-
p. 2393 - 2401
(2007/10/03)
-
- Thermal Gas Phase Hydrodehalogenation of Bromochlorodifluoromethane
-
The thermal hydrodehalogenation of bromochlorodifluoromethane (Halon-1211; CBrClF2) in the gas phase has been studied using a plug flow alumina reactor at atmospheric pressure over the temperature range 400-900 degC with residence times of 2-3 s and CBrClF2/hydrogen molar intake ratios of ca. 10.Conversion of CBrClF2 starts at ca. 400 degC with C-Br bond homolysis followed by reaction with HX (X being Br, Cl or H) to yield CHClF2.At higher temperatures other products arise and complete conversion of CBrClF2 is achieved at ca. 600 degC.At temperatures above 850 degC complete dehalogenation to mainly methane (yield 80percent) is attained.In the temperature range 450-550 degC the (pseudo) first-order rate constant for the overall reaction (F) was found to obey: log (kF/s-1) = (9.4 +/- 1.5) - (150 +/- 25) kJ mol-1/2.303RT.The thermolysis of CBrClF2 was also studied using an excess of 2-phenylpropane (cumene) as a radical scavenger, resulting in the following Arrhenius expression for reaction (G): log (kG/s-1) = (15.1 +/- 0.5) - (262 +/- 9) kJ mol-1/2.303RT.From these parameters the bond dissociation energy for the C-Br bond in CBrClF2 was calculated to be 268 +/- 8 kJ mol-1, leading to a heat of formation of the CClF2-radical of -279 +/- 17 kJ mol-1.Kinetic analysis and separate experiments with H2O2 as an initiator for making H-radical showed that attack by H-radical is the main route for decomposition of CBrClF2.At temperatures higher than 500 degC HBr rather than H2 acts as a hydrogen transfer agent resulting in a fast radical chain (reactions G and L-O) with the observed Arrhenius parameters as a consequence.
- Lijser, Huub J. P. de,Louw, Robert,Mulder, Peter
-
p. 139 - 146
(2007/10/02)
-
- Kinetics of the Reactions of Halogenated Methyl Radicals with Molecular Bromine
-
The kinetics of seven reactions of halogenated methyl radicals (CH2Cl, CHCl2, CFCl2, CF2Cl, CF3, CH2Br, and CH2I) with molecular bromine were studied by using a heatable tubular reactor coupled to a photoionization mass spectrometer.Rate constants were measured as a function of temperature, typically between 296 and 532 K.Arrhenius activation energies were found to be small negative values (typically -2 kJ mol-1) for all reactions studied with the exception of that of the CF3 + Br2 reaction (whose activation energy is positive, but which could not determined accurately).The pattern of reactivity among 11 reactions of substituted methyl radicals with Br2 (which includes the 7 reactions studied here and 4 C(H)x(CH3)3-x + Br2 reactions (x = 0-3) studied earlier) has been accounted for by the inductive effect of the substituent atoms or groups.The sum of the Pauling electronegativities of these substituents provides a useful measure of their total inductive effect on the reaction rate constant.
- Timonen, R. S.,Seetula, J. A.,Niiranen, J.,Gutman, D.
-
p. 4009 - 4014
(2007/10/02)
-
- Kinetic Isotope Effects for Proton Abstraction from Methanol by Polyhalogenomethyl Carbanions. Cleavage of Me3SiCHX2 and Me3SiCX3 by Base in Methanol.
-
The carbanions XxH(3-x)C- (X=Cl or Br; x=2 or 3) generated by base cleavage of Me3SiCH(3-x)Xx (or some related compounds) in MeOH, show a kinetic isotope kH/kD of ca. 1.1 in proton abstraction from methanol, as given by the product ratio XxH(3-x)CH/XxH(3-x)CD observed for reaction in MeOH-MeOD (1:1) at ca. 21 deg C.The low value of the isotope effect is attributed to the fact that the free electron pair in the carbanion is localized on the carbon centre; carbanions derived from acids of acidities comparable with those of X3CH and X2CH2 but in which the electron pair is conjugatively delocalized, show much larger isotope effects.
- Eaborn, Colin,Stanczyk, Wlodzimierz A.
-
p. 471 - 473
(2007/10/02)
-
- Iodine Atoms and Iodomethane Radical Cations: Their Formation in the Pulse Radiolysis of Iodomethane in Organic Solvents, Their Complexes, and Their Reactivity with Organic Reductants
-
Pulse radiolysis of iodomethane in various organic solvents leads to formation of iodine atoms or iodomethane radical cations, which in turn form complexes with iodomethane or with the solvent.Radiolysis in cyclohexane gives CH3I*I, which exhibits an absorption peak at 390 nm, whereas radiolysis in benzene forms the solvent complex, C6H6*I, which exhibits an intense broad absorption centered at 490 nm.Radiolysis of iodomethane in acetone, benzonitrile, and halogenated hydrocarbons results in formation of the radical cation CH3I.+.In the former two solvents, this species forms a complex with another molecule of iodomethane to give (CH3))2+, which absorbs at 420 nm, in agreement with previous results in aqueous solutions, but in halogenated hydrocarbons it forms complexes with the solvents, absorbing at 320-360 nm, i.e. near the absorption of monomeric CH3I.+ in water.Complexes of I atoms oxidize phenol and triphenylamine relatively slowly whereas complexes of CH3I.+ react more rapidly.The reactivity of the CH3I.+*RX complexes increases in the order of RX = CH2Cl2, CHCl3, CH2Br2, CCl4, CH3I, and for each complex the reactivity with phenol increases with increase in electron donating power of substituents.Replacing the methyl group of iodomethane radical cation with ethyl or isopropyl decreases the reactivity, whereas trifluoromethyl increases the reactivity.These oxidation reactions proceed via an intermediate complex between the iodine species and the organic reductant.
- Shoute, Lian C. T.,Neta, P.
-
p. 4411 - 4414
(2007/10/02)
-
- Bromine Atom Complexes with Bromoalkanes. Their Formation in the Pulse Radiolysis of Di-, Tri-, and Tetrabromomethane and Their Reactivity with Organic Reductants
-
Bromine atoms were produced in the pulse radiolysis of neat dibromomethane (DBM) and bromoform and of cyclohexane solutions containing DBM, bromoform, carbon tetrabromide, or ethyl bromide.The Br atoms form complexes with dimethyl sulfoxide (λmax 425 nm), with aromatic compounds, and with oxygen-containing compounds.In the absence of other complexing agents, since Br atoms do not abstract H from the solvents rapidly, they form complexes with their parent bromo compounds.The absorption maxima of these complexes are at 365 nm for C2H5Br*Br, 390 nm for CH2Br2*Br, 425 nm for CHBr3*Br, and 480 nm for CBr4*Br.The stability of RBr*Br appears to increase with the number of Br atoms in the molecule.These complexes act as oxidants towards p-methoxyphenol, 1,3,5-trimethoxybenzene, triphenylamine, and N,N,N',N'-tetramethyl-p-phenylenediamine.The cate constants for the oxidations were about 1E10 M-1 s-1 with CH2Br2*Br but only of the order of 1E8 - 1E9 M-1 s-1 with CBr4*Br.The initial products of the oxidation are the ion pairs between the radical cation of the organic substrate and the Br- ion.In the case of p-methoxyphenol the initial ion pair releases HBr under neutral or basic conditions to form the neutral p-methoxyphenoxyl radical.The Br atom complexes are also capable of abstracting H from weak C-H bonds.The benzylic and allylic hydrogens in hexamethylbenzene and cyclohexene are abstracted with rate constants near 1E9 by CH2Br2*Br and near 1E7 M-1 s-1 by CBr4*Br.The behavior of Br atoms is compared with that of Cl and I atoms.
- Shoute, Lian C. T.,Neta, P.
-
p. 2447 - 2453
(2007/10/02)
-
- The IR Photochemistry of Organic Compounds. II. The IR Photochemistry of Ethers: The Decomposition Patterns
-
The infrared multiple-photon decomposition (IRMPD) of saturated open-chain ethers has been systematically investigated with the intention of establishing their decomposition patterns.The main products in the IRMPD of ethers (1a-f, 2) are H2CO, CO, H2, and lower hydrocarbons.Acetaldehyde is additionally formed in the IRMPD of 1b and 1d, while acetone is formed in the IRMPD of 1d.The observed results are explained on the basis of the decomposition of the highly vibrationally excited ethers produced in the IRMPD excitation.The initial process is the homolytic cleavage of a C-O bond to yield the corresponding alkyl and alkoxyl radicals.The alkyl radicals are trapped ny Br2.Sequential splitting and addition reactions of the radicals yield primary products with a high internal energy.The primary products also decompose sequentially into stable products, in part.The sequential processes compete with collisional deactivation.Therefore, the branching ratio depends on the internal energy of the radicals and the primary products.
- Majima, Tetsuro,Ishii, Tadahiro,Arai, Shigeyoshi
-
p. 1701 - 1709
(2007/10/02)
-
- Electron Transfer Reactions in Organic Chemistry. XIV. The Reactivities of Some Polyhaloalkanes toward the Outer-Sphere Electron Transfer Reductants Co(II)sepulchrate2+ and Co(II)W12O407-
-
Rates were measured for the title reactions in CH3CN/H2O buffered at pH ca.7 at 20 or 50 deg C.The following order of reactivity toward Co(II)W12O407- was found: CBr4 > (CBrCl2)2 > CBr2Cl2 > C2Cl6 > CBrCl3 > CF3CHClBr > CHBr3 > CCl4.Only CBr4, (CBrCl2)2, CBr2Cl2 and CBrCl3 gave measurable rates of reaction with Co(II)sepulchrate2+, and with the same order of reactivity as above.Four these four substrates, a plot of log kET2+ had a slope close to 1.Qualitative product studies for the reactions with Co(II)W12O407- showed that the polyhalomethanes generally reacted by losing their heaviest halogen, while polyhaloethanes formed ethylenes by losing their havies halogen on each carbon atom.For some of the reactions, the intermediate radical formed in the first step could be trapped by N-t-butyl-α-phenylnitrone.The resulting spin adducts were detected by ESR spectroscopy.It is agrued that the rate constant difference between CBr4 and CBrCl3 supports the notion of a very short-lived intermediate anion radical.
- Eberson, Lennart,Ekstroem, Mikael
-
p. 113 - 121
(2007/10/02)
-
- Fe3O4-Catalyzed Halogen-Exchange Reactions of Polyhalomethanes
-
Triiron tetraoxide pretreated by polyhalomethane was shown to catalyze the halogen-exchange reaction of polyhalomethanes CHlBrmCln (l=1 or 2).The exchange proceeds consecutively giving, for example, CHBrCl2, CHBr2Cl, and C
- Nakada, Masahiro,Tokumoto, Sei-ichi,Hirota, Minoru
-
p. 3979 - 3984
(2007/10/02)
-
- High-Field NMR Determination of Magnetic Susceptibility Tensors and Angular Correlation Factors of Halomethanes
-
Quadropolar splittings in the high resolution deuteron spectra of deuterated haloforms (CX3(2)H, X=Cl, Br, I) and methylene halides (CX2H(2)H) have been measured at 14.35 T (93.5 MHz) and used to determine the anisotropy or asymmetry of their molecular magnetic susceptibility tensors.By combination with the known isotropic susceptibilities, the principal susceptibility tensors have been deduced and decomposed into bond susceptibility tensors.Neither the average susceptibilities nor the principal susceptibility tensor elements of the complete halomethane series follow Pascal's additivity rules.The phenomenon is tentatively attributed to a variable paramagnetic contribution perpendicular to the X-bond.Angular correlation Kirkwood g2 factors have been determined for CHCl3 and CHBr3 and are compared with available literature data.
- Bothner-By, A. A.,Dadok, J.,Mishra, P. K.,Zijl, P. C. M. Van
-
p. 4180 - 4184
(2007/10/02)
-
- HEI PHOTOELECTRON SPECTRA OF UNSTABLE MOLECULES: MONO- AND DIHALOGENOKETENES
-
HeI Photoelectron spectra are reported for the mono- and di-chloro-and-bromo-ketenes (XHC=C=O and X2C=C=O, X=Cl,Br) generated in high yield as unstable molecules from thermolysis of acid halides.The spectra are discussed and assigned by reference to the parent ketene molecule, orbital trends, and comparison with theoretical calculations.
- Colbourne, David,Westwood, Nicholas P. C.
-
p. 2049 - 2054
(2007/10/02)
-
- Photolysis of 3-Bromo-3-methyldiazirine
-
The photolysis at 354 nm of 3-bromo-3-methyldiazirine in gas phase has been studied.After a careful search of the various possibilities we have found that all available evidence points toward the intermediary formation of hot vinyl bromide, presumably via isomerization of the corresponding carbene.Its unimolecular decomposition can take place by two different paths: one is the molecular detachment of HBr and the other the radical scission of the C-Br bond.This last way of radical formation is responsible for the apparently confusing experimental data.According to our result the activation energy for the radical decomposition is closer to that of the molecular detachment than previously thought.
- Crespo, Maria T.,Figuera, Juan M.,Rodriguez, Juan C.,Utrilla, Roberto Martinez
-
p. 5790 - 5796
(2007/10/02)
-
- Catalytic Interconversion of Alkyl Halides by Gas-liquid Phase-transfer Catalysis
-
High halogen exchange conversions are achieved when a gaseous mixture of alkyl halides (chlorides, bromides, iodides) is passed over a solid bed consisting of porous inorganic supports bearing a phase-transfer catalyst under gas-liquid phase-transfer catalysis (g.l.-p.t.c.) conditions.The process is catalytic since the bed undergoes no changes once it reaches operating conditions.For example, a methylene dichloride and bromoethane mixture is converted into all the halogen-exchange products, and their statistical distribution at equilibrium depends on the original ratio of the halogens in the organic reagents.Catalytic activity is high: 200 ml of such a mixture can be converted in 1 h by passage through 200 g of alumina coated with 10 percent tetrabutylphosphonium bromide.The catalytic process is promoted by the halide anions present as Q(1+)X(1-) in the liquid phase constituted by the molten catalyst and as Na(1+)X(1-) in the solid inorganic support; the halide anions partition themselves between the liquid and solid phases as a function of their respective affinities.This catalysis depends on the diffusion, partition, and adsorption of the alkyl halides between the gaseous, liquid, and solid phases, as well as on their intrinsic nucleophilic reactivity.Mechanistic aspects and industrial applicability are discussed.
- Tundo, Pietro,Venturello, Paolo,Angeletti, Enrico
-
p. 485 - 492
(2007/10/02)
-
- Methylenesulfurtetrafluoride, CH2=SF4, Formation, Structure, and Chemistry
-
The preparation of methylenesulfurtetrafluoride, CH2=SF4, is achieved by bromine-lithium exchange on Br-CH2-SF5 at low temperatures and subsequent lithium fluoride elimination.CH2=SF4 is a colourless gas with b.p. -19 deg C and m.p. -139 deg C.The structure is essentially trigonal-bipyramidal, the methylene group occupying an equatorial position.The protons lie in the plane of the axial fluorine atoms.The molecule is rigid.The carbon-sulfur bond is best described as strong double bond with only little ylidic polarity. - The double bond undergoes numerous addition reactions with polar species under formation of cis-configurated X-CH2-SF4-Y systems.Less often elimination of SF4 and formation of carbene is observed.
- Kleemann, Gert,Seppelt, Konrad
-
p. 645 - 658
(2007/10/02)
-
- FREE-RADICAL TRANSFORMATIONS OF 2-ALKOXY-1,3-DIOXOLANES IN POLYHALOGENOALKANES
-
The free-radical transformations of 2-ethoxy-1,3-dioxolane and 2-hexyloxy-1,3-dioxolane in bromoform and chloroform were investigated.The products from these transformations are alkyl 2-halogenoalkyl carbonates, 2-halogenoethyl formates, the corresponding cyclic and linear carbonates, aldehydes, and halogenoalkanes.A scheme of homolytic transormations is proposed for 2-alkoxy-1,3-dioxolanes in polyhalogenoalkanes.
- Rol'nik, L. Z.,Kalashnikov, S. M.,Pastushenko, E. V.,Zlot-skii, S. S.,Rakhmankulov, D. L.
-
p. 1296 - 1299
(2007/10/02)
-
- PHOTOCHEMISTRY OF ALKYL HALIDES - VII. CYCLOPROPANATION OF ALKENES
-
The previously observed cyclopropanation of alkenes by irradiation of diiodomethane (1) in their presence has been studied in more detail and found to be a synthetically useful procedure which is significantly less subject to steric effects than the traditional Simmons-Smith method.The results from photocyclopropanation of a variety of alkenes are summarized in Tables 1 and 3-4.In a number of cases the photochemical procedure afforded improved results over the Simmons-Smith method, particularly with sterically congested alkenes.Cycloalkenes showed relative rates of photocyclopropanation as a function of ring size similar to those of the Simmons-Smith method (Table 5).However, the photocyclopropanation reaction exhibited steadily increasing relative rates with increasing substitution about the double bond-in contrast with the Simmons-Smith method (Table 6), in which steric effects offset increasing nucleophilicity of the alkene with increasing substitution.The α-iodocation 2 is suggested as the methylene transfer species.In the presence of lithium bromide cation 2 was trapped to afford bromoiodomethane.
- Kropp, Paul J.,Pienta, Norbert J.,Sawyer, Joy A.,Polniaszek, Richard P.
-
p. 3229 - 3236
(2007/10/02)
-
- Carbon-Halogen Bonding Studies. Halogen Redistribution Reactions between Alkyl or Acetyl Halides and Tri-n-butyltin Halides
-
The equilibrium positions have been determined for the halogen redistribution reactions of tri-n-butyltin halides with a variety of structurally different types of alkyl halides and with acetyl halides.These have been related through the reaction ΔGo values to carbon-halogen bond dissociation energy differences.It is suggested that the trends observed in the latter may provide evidence for the existence of a small steric bond weakening effect in the order C-I > C-Br > C-Cl bonds on going from methyl to primary, secondary, and tertiary alkyl halides.On the other hand, with the 2,3-? bond containing allyl, benzyl, and propargyl halides , α-haloacetones, and haloacetonitriles, there may be some type of electronic carbon-halogen bond strengthening effect which lies in order C-I > C-Br > C-Cl.Finally, for the acetyl halides, the data are in agreement with increases in bond strengths resulting from ? contributions being in the order C-Cl > C-Br > C-I.
- Friedrich, Edwin C.,Abma, Charles B.
-
p. 1367 - 1371
(2007/10/02)
-
- Catalytic Halide Exchange in Hydrocarbons Promoted by Aluminas Coated with Phosphonium Salts
-
Passing a mixture of two different alkyl halides, in the gas phase, through a column filled with alumina and a phosphonium salt, gives halide-exchange products which are collected at the outlet by condensation; the process is catalytic and allows transformations to be carried out in a continuous flow process.
- Angeletti, Enrico,Tundo, Pietro,Venturello, Paolo
-
p. 1127 - 1128
(2007/10/02)
-
- 4-PYRIMIDONE COMPOUNDS
-
The compounds are substituted isocytosines which are histamine H 2-antagonists. Two specific compounds of the present invention are 2-2-(5-methyl-4-imidazolylmethylthio)-ethylamino!-5-(3-methoxybenzyl)-4-pyrim idone and 2-2-(5-methyl-4-imidazolylmethylthio)ethylamino!-5-benzyloxy-4-pyrimidone.
- -
-
-
- ALKOXY PYRIDINE COMPOUNDS
-
The compounds are alkoxypyridine compounds which are histamine H 2-antagonists. Two specific compounds of the present invention are N-cyano-N'-methyl-N"-2-((3-methoxy-2-pyridyl)methylthio)ethyl!guanidine and 1-methylamino-1-2-(3-methoxy-2-pyridyl)methylthio)ethylamino!-2-nitroethylene. "
- -
-
-