40921-86-6Relevant articles and documents
Kinetics and Thermochemistry of R + HBr RH + Br Reactions: Determinations of the Heat of Formation of C2H5, i-C3H7, sec-C4H9, and t-C4H9
Seakins, Paul W.,Pilling, Michael J.,Niiranen, Jukka T.,Gutman, David,Krasnoperov, Lev N.
, p. 9847 - 9855 (1992)
The reactions of alkyl radicals (R = CH3, C2H5, i-C3H7, and t-C4H9) with HBr have been studied by excimer laser flash photolysis coupled with photoionization mass spectrometry.Rate constants were obtained in the following temperature ranges and provided Arrhenius parameters for each reaction (A/(cm3 molecule-1 s-1), Ea/(kJ mol-1)): R = CH3, 299-536 K ((-1.57 +/- 0.26) * 10-12, 1.6 +/- 0.6); R = C2H5, 297-530 K ((1.70 +/- 0.55) * 10-12, -4.2 +/- 1.2); R = i-C3H7, 298-530 -K ((1.58 +/- 0.38( * 10-12, -6.4 +/- 0.9); R = t-C4H9, 298-530 K ((1.37 +/- 0.47) * 10-12, -7.8 +/- 1.4).R + HBr rate constants are approximately a factor of 2 higher than previously reported.The source of this disparity is explained.The kinetics of reverse reactions, Br + RH (R = C2H6, C3H8, n-C4H10, i-C4H10), have also been investigated using laser flash photolysis/resonance fluorescence methods.Rate constants were obtained in the following temperature ranges and provided Arrhenius parameters for each reaction (same units): RH = C2H6, 473-621 K ((2.35 +/- 1.12) * 10-10, 53.3 +/- 2.1); RH = C3H8, 476-667 K ((8.78 +/- 3.00) * 10-11, 36.0 +/- 2.0); RH = n-C4H10, 447-625 K ((2.86 +/- 0.90) * 10-10, 37.7 +/- 2.0); RH = i-C4H10, 423-621 K ((1.61 +/- 0.60) * 10-10, 28.8 +/- 1.5).These results, combined with previously obtained kinetic information, were used in second- and third-law thermochemical calculations to obtain accurate determinations of the heats of formation of the C2-C4 alkyl radicals involved.Second- and third-law determinations agreed extremely closely (differences were under 1.3 kJ mol-1).The heats of formation of the radicals thus obtained are in excellent agreement with values obtained from studies of dissociation/association equilibria, within 2.6 kJ mol-1.Recommended alkyl-radicals heats of formation (with uncertainties) at 298 K are provided that are based on an assessment of all the results of the current study and a review of other recent determinations (kJ mol-1): C2H5, 121.0 +/- 1.5; i-C3H7, 90.0 +/- 1.7; sec-C4H9, 67.5 +/- 2.2; t-C4H9, 51.3 +/- 1.8.Accurate determinations of carbon-hydrogen bond enthalpies (298 K) are provided that are based on these heats of formation (kJ mol-1): primary C-H in C2H6 (422.8 +/- 1.5); secondary C-H in C3H8 (412.7 +/- 1.7) and in n-C4H10 (411.1 +/- 2.2); tertiary C-H in i-C4H10 (403.5 +/- 1.8).
Hydrogenolysis of Alkanes. Part 4. - Hydrogenolysis of Propane, n-Butane and Isobutane over Pt/Al2O3 and Pt-Re/Al2O3 Catalysts
Bond, Geoffrey C.,Gelsthorpe, Michael R.
, p. 3767 - 3784 (1989)
The hydrogenolysis of propane, n-butane and isobutane on Pt/Al2O3 (0.3 and 0.6 percent Pt) and on Pt-Re/Al2O3 (0.3 percent Pt, 0.3 percent Re) has been investigated by a thermal cycling technique that permits evaluation of initial rates of deactivation and of consequential changes in product distributions.Less deactivation is found with propane than with the butanes; with n-butane on Pt/Al2O3 catalysts, two types of sites are apparent, one of which, having a higher probability of giving central C-C bond fission, is selectively deactivated.However, the relative chances of desorption and of further hydrogenolysis of the adsorbed intermediates are the same at both types of site.With the Pt-Re/Al2O3 catalyst, further bond-breaking in the adsorbed species formed from all three alkanes is relatively more favoured than with the Pt/Al2O3 catalysts, and with n-butane the chance of central bond-fission is enhanced.No changes in product distribution result from initial deactivation, which is comparable to that found with Pt/Al2O3 catalysts.Isomerisation of n-butane is slight (3 percent) on all three catalysts.Multiply adsorbed species are suggested as possible intermediates, and differences in product selectivities are attributed chiefly to variations in electron density at the active site.
In situ study of the interaction between tert-butyl chloride and aluminum activated with liquid in-ga eutectic
Arbuzov,Drozdov,Likholobov,Trenikhin,Talsi,Kudrya
, p. 354 - 358 (2010)
The interaction between tert-butyl chloride and activated aluminum was studied by attenuated total reflectance Fourier transform infrared spectroscopy near room temperature (18-25°C). A long induc- tion period of ?240-260 min was observed. The AlCl4- ionic aluminum chloride complexes [AlnCl3n+1]-(n = 1, 2) and the molecular species AlCl3 were identified at the activated aluminum/tert-butyl chloride interface during the reaction. The formation of the ion in the liquid medium and the presence of the same ion and a molecular AlCl3 -tert-butyl chloride complex in the resinous products of the reaction were confirmed by 27Al NMR spectroscopy. The reaction products were analyzed qualitatively by GC/MS. The reactivities of activated aluminum and anhydrous aluminum chloride toward tert-butyl chloride under the same conditions were compared. A distinctive feature of the interaction activated aluminum and tert-butyl chloride is the dominant formation of the AlCl4 -ion. By contrast, the interaction between aluminum chloride and tert-butyl chloride yields the polynuclear ion and,Al2Cl7 - likely,Al3Cl10-. Pleiades Publishing, Ltd., 2010.
SRN1 Reactions of t-Butyl Chlorides
Santiago, Ana N.,Rossi, Roberto A.
, p. 206 - 208 (1990)
t-Butyl chloride and 2-chloro-2-methyl-1-phenylpropane reacted with Ph2P- ions under irradiation to give reduction and substitution products and 6-chloro-6-methylhept-1-ene (used as a radical probe) reacted to give the cyclized substitution product.The bromides gave only elimination products.
The Mechanism of the Reaction between Silyl Radicals and Chloroethylenes: A Case Study of the Et3Si-C2Cl4 Reaction
Horowitz, Abraham
, p. 318 - 321 (1985)
The photolysis and radiolysis of C2Cl4 solutions in Et3SiH were studied at 298 K.The main products, Et3SiCl and C2Cl3H, are formed in equal yields and via a free radical chain mechanism, as indicated by the high quantum yields (ca.500) and G values (ca.1600).The reactions C2Cl3+Et3SiH->C2Cl3H+Et3Si (3) and Et3Si+C2Cl4->Et3SiCl+C2Cl3 (4) constitute the chain propagation step.Competitive studies yield k4/k11 of 0.18+/-0.01 (2?) where Et3Si+t-BuCl->Et3SiCl+t-Bu (11).The mechanistic implications and consequences of the observation that the reaction of Et3Si radicals with C2Cl4 results almost exclusively in Cl transfer rather than addition are discussed, and the conclusions are generalized for similar reactions of other chloroethylenes.
Physicochemical Properties and Isomerization Activity of Chlorinated Pt/Al2O3 Catalysts
Melchor, Antonio,Garbowski, Edouard,Mathieu, Michel-Vital,Primet, Michel
, p. 3667 - 3680 (1986)
Alumina-supported platinum catalysts with various metal contents have been prepared and chlorinated by CCl4 at 473 and 573 K.Their acidity has been measured by pyridin adsorption and catalytic activity in n-butane isomerization.The state of platinum has been followed by infrared spectroscopy, whereas the modifications of the dispersion were measured by electron microscopy and by H2-O2 titrations.The presence of metal in chlorinated alumina produces only small changes in acidity but a great enhancement in isomerization activity for samples chlorinated at 573 K.After chlorination, platinum is oxidized to platinum chloride, which reacts with AlCl3 to produce the PtCl2*2AlCl3 complex.This complex is mobile on the suport and agglomerates in large particles.During the isomerization of n-butane, platinum is reduced in the metallic state leading to very low metal dispersion.Very small platinum clusters are also present, they are able to perform the hydrogenation of butenes and to decrease the coke formation.This ageing is limited in comparison with pure alumina.The possible role of HCl leading to superacid species is also discussed.
n-PENTANE ISOMERIZATION OVER SUPPORTED BINARY IODIDE CATALYSTS PREPARED FROM INTERMETALLIC-I2 SYSTEMS
Imamura, Hayao,Soga, Kazuo,Sato, Masaru,Wallace, W. E.
, p. 957 - 958 (1980)
γ-Al2O3 or SiO2 supported binary iodide catalysts, which were prepared by impregnation of the mixtures formed from reacting ErAl3 with I2, exhibited the high ability to catalyze the n-pentane conversion at room temperature.The conversion easily progressed to form iso-pentane along with production of C4 and C6 hydrocarbons.Properties of the catalysts prepared closely related to supports used.
A highly active solid superacid catalyst for n-butane isomerization: Persulfate modified Al2O3-ZrO2
Xia,Hua,Tang,Gao
, p. 1899 - 1900 (1999)
A new solid superacid catalyst of persulfate modified Al2O3ZrO2 has been prepared for the first time; it displays extraordinarily high catalytic activity and stability for the isomerization of n-butane.
Sulfated Zirconia-catalyzed Alkylation of Phenol with Camphene and Isomerization of n-butane
Popova, Svetlana A.,Chukicheva, Irina Yu.,Kutchin, Alexander V.,Tarasov, Andrei L.,Kustov, Leonid M.
, p. 98 - 99 (2014)
Sulfated zirconia modified with polyvalent cations is capable of catalyzing alkylation of phenol with camphene and isomerization of utane into isobutane.
Hydrogen Activation and Hydrogenolysis Facilitated by Late-Transition-Metal-Aluminum Heterobimetallic Complexes
Charles, R. Malcolm,Yokley, Timothy W.,Schley, Nathan D.,Deyonker, Nathan J.,Brewster, Timothy P.
, p. 12635 - 12645 (2019)
Previously reported heterobimetallic rhodium-aluminum and iridium-aluminum alkyl complexes are shown to activate hydrogen, generating the corresponding alkane. Kinetic data indicate a mechanistic difference between the iridium- A nd rhodium-based systems. In both cases the transition metal is an active participant in the release of alkane from the aluminum center. For iridium-aluminum species, experimental mechanistic data suggest that multiple pathways occur concomitantly with each other: One being the oxidative addition of hydrogen followed by proton transfer resulting in alkane generation. Computational data indicate a reasonable barrier to formation of an iridium dihydride intermediate observed experimentally. In the case of the rhodium-aluminum species, hydrides are not observed spectroscopically, though a reasonable barrier to formation of this thermodynamically unstable species has been calculated. Alternative mechanistic possibilities are discussed and explored computationally. Cooperative hydrogenolysis mechanisms are computed to be energetically unfeasible for both metal centers.
