T:Toxic;
74-83-9Relevant academic research and scientific papers
Catalytic dealkylation of phosphates with binuclear boron compounds
Keizer, Timothy S.,De Pue, Lauren J.,Parkin, Sean,Atwood, David A.
, p. 1864 - 1865 (2002)
The Salen(tBu) ligand and its derivatives were used to prepare binuclear boron complexes. These compounds have the formula, L(BBr2)2 (L = Salpen(tBu) and Salben(tBu)). These are formed from the reaction of the corresponding L[B(OMe)2]2 with BBr3. They represent a new type of binuclear boron compound. These compounds are active towards the dealkylation of many phosphates. They are also catalytically active with a stoichiometric amount of BBr3 to trimethylphosphate. Copyright
Effect of 1-Butanol upon SN2 Reactions in Cationic Micelles. A Quantitative Treatment
Bertoncini, Clelia R. A.,Nome, Faruk,Cerichelli, Giorgio,Bunton, Clifford A.
, p. 5875 - 5878 (1990)
Observed first-order rate constants for reaction of methyl naphthalene-2-sulfonate (2-MeONs) with Br- in cetyltrimethylammonium and cetyltriethylammonium bromides (CTABr and CTEABr) are decreased by addition of 1-butanol.The inhibition can be treated quantitatively in terms of a pseudophase model in which the rate constant at the micellar surface follows the mole ratio of bound Br- to micellized surfactant and bound 1-BuOH.The second-order rate constants in the micellar pseudophase, kM, are independent of in the range 0-0.9 M.Conductometry and NMR line widths of 81Br- show that the alcohol reduces micellar binding of Br-, and spectral absorbance shows that binding of 2-MeONs is also reduced.
Concentration and medium micellar kinetic effects caused by morphological transitions
Graciani, Maria Del Mar,Rodriguez, Amalia,Martin, Victoria Isabel,Fernandez, Gaspar,Moya, Maria Luisa
, p. 18659 - 18668 (2010)
The reaction methyl naphthalene-2-sulfonate + Br- was investigated in several alkanediyl-α-ω-bis(dodecyldimethylammonium) bromide, 12-s-12,2Br- (with s = 2, 3, 4, 5, 6, 8, 10, 12), micellar solutions in the absence and in the presence of various additives. The additives were 1,2-propylene glycol, which remains in the bulk phase, N-decyl N-methylglucamide, MEGA10, which forms mixed micelles with the dimeric surfactants, and 1-butanol, which distributes between the aqueous and micellar phases. Information about the micellar reaction media was obtained by using conductivity and fluorescence measurements. In all cases, with the exception of water-1,2-prop 12-5-12,2Br- micellar solutions, with 30% weight percentage of the organic solvent, a sphere-to-rod transition takes place upon increasing surfactant concentration. In order to quantitatively explain the experimental data within the whole surfactant concentration range, a kinetic equation based on the pseudophase kinetic model was considered, together with the decrease in the micellar ionization degree accompanying micellar growth. However, theoretical predictions did not agree with the experimental kinetic data for surfactant concentrations above the morphological transition. An empirical kinetic equation was proposed in order to explain the data. It contains a parameter b which is assumed to account for the medium micellar kinetic effects caused by the morphological transition. The use of this empirical equation permits the quantitative rationalization of the kinetic micellar effects in the whole surfactant concentration range.
The selective high-yield conversion of methane using iodine-catalyzed methane bromination
Ding, Kunlun,Metiu, Horia,Stucky, Galen D.
, p. 474 - 477 (2013)
Methyl bromide is used as feed in a process that converts it to gasoline. It is prepared by the gas-phase reaction of CH4 with Br2, a reaction that produces, besides the desired CH3Br, large amounts of CH2Br2. The latter cokes the catalyst used for gasoline production. The separation of CH2Br2 by distillation makes gasoline production too expensive. It is therefore important to increase the selectivity of the bromination reaction. We show that a small amount of I 2 catalyzes the reaction CH2Br2 + CH 4 → 2CH3Br, which leads to higher CH4 conversion and higher selectivity to CH3Br. These findings are promising for developing a low-cost integrated bromine-iodine based dual-halogen pathway to convert stranded natural gas into fuels and chemicals.
An Activated TiC–SiC Composite for Natural Gas Upgrading via Catalytic Oxyhalogenation
Zichittella, Guido,Puértolas, Bego?a,Siol, Sebastian,Paunovi?, Vladimir,Mitchell, Sharon,Pérez-Ramírez, Javier
, p. 1282 - 1290 (2018)
Alkane oxyhalogenation has emerged as an attractive catalytic route for selective natural gas functionalization to important commodity chemicals, such as methyl halides or olefins. However, few systems have been shown to be active and selective in these reactions. Here, we identify a novel and highly efficient TiC–SiC composite for methane and ethane oxyhalogenation. Detailed characterization elucidates the kinetics and mechanism of the selective activation under reaction conditions to yield TiO2–TiC–SiC. This catalyst outperforms bulk TiO2, one of the best reported catalysts, reaching up to 85 % selectivity and up to 3 times higher titanium-specific space-time-yield of methyl halides or ethylene. This is attributed to the fact that the active TiO2 phase generated in situ is embedded in the thermally conductive SiC matrix, facilitating heat dissipation thus improving selectivity control.
Kinetic Study of CH3 + HBr and CH3 + Br Reactions by Laser Photolysis-Transient Absorption over 1-100 Bar Pressure Range
Krasnoperov, Lev N.,Mehta, Kashyap
, p. 8008 - 8020 (1999)
Reactions of methyl radicals with hydrogen bromide CH3 + HBr -> CH4 + Br (1) and bromine atoms CH3 + Br -> CH3Br (2) were studied using excimer laser photolysis-transient UV spectroscopy at 297 +/- 3 K over the 1-100 bar buffer gas (He) pressure range. Methyl radicals were produced by 193 nm (ArF) laser photolysis of acetone, (CH3)2CO, and methyl bromide, CH3Br. Temporal profiles of methyl radicals were monitored by UV absorption at 216.51 nm (copper hollow cathode lamp with current boosting). The yield of acetyl radicals in photolysis of acetone at 193 nm was found to be less than 5 percent at 100 bar He based on the transient absorptions at 222.57 and 224.42 nm. The measured rate constants for reaction 1 are k1 = (2.9 +/-0.7)E-12, (3.8 +/- 1.5)E-12, and (3.4 +/- 1.3)E-12 cm3 molecule-1 s-1 at the buffer gas (He) pressures of 1.05, 11.2, and 101 bar, respectively. The rate data obtained in this study confirmed high values of the previous (low pressure) measurements and ruled out the possibility of interference of excited species. The measured rate constant is independent of pressure within the experimental error. The rate constant of reaction of methyl radicals with bromine atoms (2) was determined relative to the rate constant of methyl radical self reaction, CH3 + CH3 -> C2H6 (3) in experiments with photolysis of CH3Br: k2/k3 = 0.92 +/- 0.32, 1.15 +/- 0.30, and 1.65 +/- 0.26 at 1.05, 11.2, and 101 bar He, respectively. On the basis of the literature data for reaction 3, this yields k2 = (5.8 +/- 2.2)E-11, (7.4 +/- 2.2)E-11, (10.7 +/- 2.3)E-11, and (11.9 +/- 2.5) E-11 cm3 molecule-1 s-1 at 1 .05, 1 1.2, 101 bar (He), and in the high-pressure limit, respectively.
Kinetics of methoxy-NNO-Azoxymethane hydrolysis in strong acids
Zyuzin,Lempert
, p. 17 - 25 (2011)
The kinetics of methoxy-NNO-azoxymethane (I) hydrolysis in concentrated solutions of strong acids (HBr, HCl, HClO4, and H2SO 4) has been investigated by a manometric method. The gas evolution rate is described by the equation corresponding to two consecutive first-order reactions, with the rate constant of the second reaction considerably exceeding the rate constant of the first reaction, i.e., k 2 {ie17-1} k 1. The temperature dependences of k 1 (s-1) in 47.59% HBr in the temperature range from 60 to 90°C and in 64.16% H 2SO4 between 80 and 130°C are described by Arrhenius equations with IogA= 12.7 ± 1.5 and 13.6 ± 1.4 and E a = 115 ± 10 and 137 ± 10 kJ/mol, respectively. The parameters of the Arrhenius equation for the rate constant k 2 for the reaction in 64.16% H2SO4 between 80 and 130°C are IogA= 9.1 ± 2.5 and E a = 91 ± 18 kJ/mol. An analysis of the UV spectra of compound I in concentrated H2SO4 shows that I is a weak base (pKBH+ ≈ - 6). The rate-determining step of the hydrolysis of I is the attack of the nucleophile on the carbon atom of the MeO group of the protonated molecule of I. The resulting methyldiazene dioxide decomposes via a complicated mechanism to evolve N2, NO, and N2O. The pseudo-first-order rate constant k 1 of the reaction at 80°C depends strongly on the acid concentration and on the type of nucleophile (Br-, Cl-, or H2O). The relationship between k 1 and the rate constant k of the bimolecular nucleophilic substitution reaction (SN2) is given by the linear equation log [k1/(CH + CNu)] = m ≠ mX 0 + log (k/KBH+), where CH + and C Nu are the concentrations of H+ and nucleophile, respectively; X 0 is the excess acidity; and m and m are coefficients. The Swain-Scott equation log (kNu/kH2 O) = ns, where n is the nucleophilicity factor and s is the substrate constant (s = 0.72), is applicable to the rate constants k of the S N2 reactions of the protonated molecule of I with Br-, Cl-, and H2O.
Study of the bromide ion reaction with methyl naphthalene-2-sulfonate in water-DMSO TTAB micellar solutions
Moya, Maria Luisa,Rodriguez, Amalia,Munoz, Maria,Del Mar Graciani, Maria,Fernandez, Gaspar
, p. 676 - 682 (2006)
The reaction of bromide ions with methyl naphthalene-2-sulfonate (MeNS) has been investigated in water-dimethyl sulfoxide, DMSO, tetradecyltrimethylammonium bromide, TTAB, micellar solutions, with the weight percentage of DMSO up to 50%. In order to quantitatively rationalize the micellar kinetic effects observed, conductivity, surface tension, and steady-state fluorescence measurements were used to get information about the micellar reaction media. Results showed that changes caused by the addition of different amounts of DMSO to TTAB aqueous micellar solutions are made evident from the kinetic micellar effects, these being a helpful tool to obtain information on the micellar reaction media in the presence of the added organic solvent. Copyright
Kinetics of Reactions of Halogenated Methyl Radicals with Hydrogen Iodide
Seetula, Jorma A.,Gutman, David
, p. 3626 - 3630 (1991)
The kinetics of the reactions of CH2I, CH2Br, CH2Cl, and CHCl2 with HI were studied in a tubular reactor coupled to a photoionization mass spectrometer.Rate constants were measured as a function of temperature (typically between 294 and 552 K) to determine Arrhenius parameters.For these and other R + HI reactions studied to date (i.e., those involving aklyl radicals), a linear free energy relationship was dicovered which correlates the large differences in reactivity among all these R + HI reactions with the inductive effect of the substitutent atoms or groups on the central carbon atom.
Trialkylammonium salt degradation: Implications for methylation and cross-coupling
Assante, Michele,Baillie, Sharon E.,Juba, Vanessa,Leach, Andrew G.,McKinney, David,Reid, Marc,Washington, Jack B.,Yan, Chunhui
, p. 6949 - 6963 (2021/06/02)
Trialkylammonium (most notably N,N,N-trimethylanilinium) salts are known to display dual reactivity through both the aryl group and the N-methyl groups. These salts have thus been widely applied in cross-coupling, aryl etherification, fluorine radiolabelling, phase-transfer catalysis, supramolecular recognition, polymer design, and (more recently) methylation. However, their application as electrophilic methylating reagents remains somewhat underexplored, and an understanding of their arylation versus methylation reactivities is lacking. This study presents a mechanistic degradation analysis of N,N,N-trimethylanilinium salts and highlights the implications for synthetic applications of this important class of salts. Kinetic degradation studies, in both solid and solution phases, have delivered insights into the physical and chemical parameters affecting anilinium salt stability. 1H NMR kinetic analysis of salt degradation has evidenced thermal degradation to methyl iodide and the parent aniline, consistent with a closed-shell SN2-centred degradative pathway, and methyl iodide being the key reactive species in applied methylation procedures. Furthermore, the effect of halide and non-nucleophilic counterions on salt degradation has been investigated, along with deuterium isotope and solvent effects. New mechanistic insights have enabled the investigation of the use of trimethylanilinium salts in O-methylation and in improved cross-coupling strategies. Finally, detailed computational studies have helped highlight limitations in the current state-of-the-art of solvation modelling of reaction in which the bulk medium undergoes experimentally observable changes over the reaction timecourse. This journal is
