- Stereoselective Photooxidation of trans-2-Butene to Epoxide by Nitrogen Dioxide Excited with Red Light in a Cryogenic Matrix
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Reaction was induced between trans-2-butene and nitrogen dioxide by exciting trans-butene-NO2 pairs, isolated in solid Ar at red, yellow, and green wavelengths (NO22B2 2A1).The chemistry was monitored by FT-infrared spectroscopy, and Ar ion and cw dye lasers were used for photolysis.Products formed were 2-butene oxide + NO, the former under complete retention of stereochemistry, and an addition product that was identified by (18)O isotopic substitution as a butyl nitrite radical, reported here for the first time.Analysis of the photolysis-wavelengthdependence of the butyl nitrite radical and trans-2-butene oxide (NO) growth kinetics revealed that epoxide + NO is formed along two reaction pathways.The first gives trans-2-butene oxide + NO and butyl nitrite radical upon absorption of a single photon by trans-2-butene-NO2 pairs (one photon path).The second path is formation of trans-2-butene oxide + NO by photodissociation of trapped butyl nitrite radical by a (second) red or shorter wavelength photon (two-photon path).Two alternative transients are proposed for the one-photon path, namely a hot butyl nitrite radical and an oxirane biradical, respectively.The wavelength dependence of the product branching along the one-photon path indicates that branching occurs from a vibrationally unrelaxed transient.This suggests that the observed stereochemical integrity originates from insufficient coupling of the stretching and bending vibrations of the transient with torsion around its central C-C bond on the time scale of reaction to epoxide + NO and its stabilization as butyl nitrite radical.
- Nakata, Munetaka,Frei, Heinz
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Read Online
- PROCESS FOR SYNTHESIS OF PICOLINAMIDES
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The present technology relates to processes, mixtures and intermediates useful for making picolinamide fungicides. The picolinamide compounds are prepared by processes that include coupling together a 4-methoxy-3-acyloxypicolinic acid with key 2-amino-L-alaninate esters derived from substituted 2-phenylethanols.
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Paragraph 0236
(2021/04/23)
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- 2,3-Butanediol dehydration catalyzed by silica-supported alkali phosphates
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Characterization of acid-base centers and catalytic dehydration of 2,3-butanediol (BDO) was performed over a wide range of silica-supported alkali phosphates (M_P/SiO2; M = Na, K, Cs; M:P = 0.5–3 mol:mol). Selectivity to 1,3-butadiene (BD) and 3-butene-2-ol (3B2OL) formed by elimination correlates with the densities of conjugated acid-base pairs and increases in the order Na ??M+ moieties. Isolated Br?nsted acid centers are probably silica grafted phosphoric acid molecules at low M/P and –PO(OH)2 end groups of oligophosphates at M/P > 1.5. Deactivation rate increases with the increase of M/P ratio in order Na K Cs. Deactivation patterns imply that sites responsible for elimination are active in dehydrative epoxidation. Dehydration of 3B2OL smoothly proceeds to BD, but the catalysts deactivate faster compared to BDO dehydration.
- Kim, Wooyoung,Shin, Wookyun,Lee, Kyoung Jun,Cho, YongSeok,Kim, Hyung Soon,Filimonov, Igor N.
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p. 148 - 163
(2018/11/26)
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- Oxidation of lower alkenes by Α-oxygen (FeIII–O??)Α on the FeZSM-5 surface: The epoxidation or the allylic oxidation?
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Reactions of anion-radical α-oxygen (FeIII–O??)α with propylene and 1-butene on sodium-modified FeZSM-5 zeolites were studied in the temperature range from ?60 to 25 °C. Products were extracted from the zeolite surface and identified. It was found that main reaction pathway was the epoxides formation. Selectivity for epoxides at ?60 °C was 59–64%. Other products were formed as a result of secondary transformations of epoxides on the zeolite surface. According to IR spectroscopy, the oxidation of propylene over the entire temperature range and 1-butene at ?60 °C were not accompanied by the formation of (FeIII–OH)α groups, in distinction to methane oxidation. This testifies that hydrogen abstraction does not occur. In case of 1-butene reaction with α-oxygen at 25 °C, hydrogen abstraction occurred but was insignificant, ca 7%. According to DFT calculation ferraoxetane intermediate formation is preferable over hydrogen abstraction. Following decomposition of this intermediate leads to the propylene oxide (PO) formation. The results may be relevant to the low selectivity problem of the silver catalyst in propylene epoxidation and raise doubts about the presently accepted mechanism explaining an adverse effect of allylic hydrogen.
- Starokon, Eugeny V.,Malykhin, Sergei E.,Parfenov, Mikhail V.,Zhidomirov, Georgy M.,Kharitonov, Alexander S.
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- A method for preparing epoxy butane
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The invention relates to a method for preparing epoxy butane, which comprises the following step: in an isopropyl benzene solution containing 25 wt% of cumene hydroperoxide solute, preparing epoxy butane from butylene oxide by using the cumene hydroperoxide solute as an oxidizer and a titanium-silicon molecular sieve with three-dimensional pore canal structure as a catalyst, wherein the fixed bed reaction conditions are as follows: the mole ratio of butylene to the cumene hydroperoxide solute is (5.0-12.0):1, the weight hourly space velocity of the cumene hydroperoxide is 1.0-5.0 h, the reaction pressure is 1.0-6.0 MPa, and the temperature is 60.0-120.0 DEG C. The catalyst is the titanium-silicon molecular sieve with three-dimensional pore canal structure; the molecular sieve has hysteresis loop on the low-temperature nitrogen adsorption and desorption isotherm; the average pore size is 2.0-8.0nm, and the specific area is 650.0-1100.0 m/g; and the catalyst has the advantages of favorable activity and high epoxy butane selectivity, and can be widely popularized and applied to industrial production of epoxy butane by butylene epoxidation.
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Paragraph 0019; 0020
(2017/03/08)
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- Gas-phase dehydration of vicinal diols to epoxides: Dehydrative epoxidation over a Cs/SiO2 catalyst
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A novel type of dehydration reaction that produces epoxides from vicinal diols (dehydrative epoxidation) using a basic catalyst is reported. Epoxyethane, 1,2-epoxypropane, and 2,3-epoxybutane were produced from the dehydrative epoxidation of ethylene glycol, 1,2-propanediol, and 2,3-butanediol, respectively. Among a number of tested basic catalysts, the Cs/SiO2 catalyst showed outstanding performance for the dehydrative epoxidation of 2,3-butanediol and is considered to be the most promising catalyst for this type of reaction. In order to identify the superiority of the Cs/SiO2 catalyst and a mechanism of the reaction, structure-activity relationships were studied along with density functional theory (DFT) calculations. The following features are found to be responsible for the excellent activity of the Cs/SiO2 catalyst: i) strong basic sites formed by Cs+, ii) low penetration of Cs+ into SiO2 which permits basic sites to be accessible to the reactant, iii) stable basic sites due to the strong interactions between Cs+ and SiO2 surface, and iv) mildly acidic surface of SiO2 which is advantageous for the elimination to H2O. In addition, the dehydrative epoxidation involves an inversion of chirality (e.g. meso-2,3-butanediol (R,S) to trans-2,3-epoxybutane (R,R or S,S)), which is in agreement with DFT results that the reaction follows a stereospecific SN2-like mechanism.
- Kim, Tae Yong,Baek, Jayeon,Song, Chyan Kyung,Yun, Yang Sik,Park, Dae Sung,Kim, Wooyoung,Han, Jeong Woo,Yi, Jongheop
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- A comprehensive test set of epoxidation rate constants for iron(IV)-oxo porphyrin cation radical complexes
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Cytochrome P450 enzymes are heme based monoxygenases that catalyse a range of oxygen atom transfer reactions with various substrates, including aliphatic and aromatic hydroxylation as well as epoxidation reactions. The active species is short-lived and difficult to trap and characterize experimentally, moreover, it reacts in a regioselective manner with substrates leading to aliphatic hydroxylation and epoxidation products, but the origin of this regioselectivity is poorly understood. We have synthesized a model complex and studied it with low-pressure Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry (MS). A novel approach was devised using the reaction of [FeIII(TPFPP)]+ (TPFPP = meso-tetrakis(pentafluorophenyl)porphinato dianion) with iodosylbenzene as a terminal oxidant which leads to the production of ions corresponding to [FeIV(O)(TPFPP+a?￠)]+. This species was isolated in the gas-phase and studied in its reactivity with a variety of olefins. Product patterns and rate constants under Ideal Gas conditions were determined by FT-ICR MS. All substrates react with [FeIV(O)(TPFPP+a?￠)]+ by a more or less efficient oxygen atom transfer process. In addition, substrates with low ionization energies react by a charge-transfer channel, which enabled us to determine the electron affinity of [FeIV(O)(TPFPP+a?￠)]+ for the first time. Interestingly, no hydrogen atom abstraction pathways are observed for the reaction of [FeIV(O)(TPFPP+a?￠)]+ with prototypical olefins such as propene, cyclohexene and cyclohexadiene and also no kinetic isotope effect in the reaction rate is found, which suggests that the competition between epoxidation and hydroxylation - in the gas-phase - is in favour of substrate epoxidation. This notion further implies that P450 enzymes will need to adapt their substrate binding pocket, in order to enable favourable aliphatic hydroxylation over double bond epoxidation pathways. The MS studies yield a large test-set of experimental reaction rates of iron(iv)-oxo porphyrin cation radical complexes, so far unprecedented in the gas-phase, providing a benchmark for calibration studies using computational techniques. Preliminary computational results presented here confirm the observed trends excellently and rationalize the reactivities within the framework of thermochemical considerations and valence bond schemes.
- Sainna, Mala A.,Kumar, Suresh,Kumar, Devesh,Fornarini, Simonetta,Crestoni, Maria Elisa,De Visser, Sam P.
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p. 1516 - 1529
(2015/03/04)
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- Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide by Using Bifunctional One-Component Phosphorus-Based Organocatalysts
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Numerous bifunctional organocatalysts were synthesized and tested for the atom-efficient addition of carbon dioxide and epoxides to produce cyclic carbonates. These catalysts are based on phosphonium salts containing an alcohol moiety in the side chain for substrate activation through hydrogen bonding. In the model reaction, converting 1,2-butylene oxide with CO2, 19 catalysts were tested to determine structure-activity relationships. In total, 28 epoxides were converted with CO2 to give the respective cyclic carbonates in yields of up to 99%. Even at 45C, the most active catalyst was able to produce cyclic carbonates selectively in high yields. The carbonates were generally obtained as analytically pure products after simple filtration over silica gel. This single-component catalyst system works under neat and mild reaction conditions and tolerates several useful moieties. Two heads are better than one! Bifunctional organocatalysts are synthesized and tested in the catalytic reaction of epoxides and carbon dioxide to give the respective cyclic carbonates. Product formation is significantly increased by hydrogen-bond donation from the bifunctional phosphonium catalyst.
- Büttner, Hendrik,Steinbauer, Johannes,Werner, Thomas
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p. 2655 - 2669
(2015/09/02)
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- Catalytic epoxidation of olefins in the presence of a vanadyl porphyrin complex
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It was found that vanadyl porphyrin complexes synthesized from petroleum metal porphyrin concentrates stimulated epoxidation during the olefin oxygenation process. The yields of obtained oxiranes turned out to be 38-75%, depending on the olefin structure. An epoxidation mechanism that suggests the formation of a protonated dioxygen adduct as an intermediate during oxygenation of olefins in the presence of vanadyl porphyrin complexes was proposed. An analogy is drawn between the epoxide formation reaction upon the catalytic oxygenation of olefins and the Prilezhaev reaction. MAIK "Nauka/Interperiodica".
- Miralamov,Mamedov
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- Surface-modified mixed oxides containing noble metal and titanium for the selective oxidation of hydrocarbons
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This invention relates to a process for the production of a composition containing gold and/or silver particles, mixed oxides containing titanium and silicon which have been surface-modified, to the compositions producible in this process and to the use thereof in processes for the selective oxidation of hydrocarbons in the presence of oxygen and a reducing agent. The catalytically active compositions exhibit constantly high selectivities and productivities.
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- Sol-gel hybrid materials containing precious metals as catalysts for partial oxidation of hydrocarbons
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The present invention relates to a process for preparing a composition containing gold and/or silver particles and an amorphous, organic/inorganic titanium/silicon mixed oxide, the compositions which can be prepared by this process and their use as catalysts for the selective oxidation of hydrocarbons.
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- Epoxidation of olefins at low temperature using m-chloroperbenzoic acid
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Epoxidation of olefins using m-chloroperbenzoic acid in dichloromethane without catalyst at low temperature is described.
- Srinivasan,Chandrasekharam,Vani,Chida, A. Seema,Singh
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p. 1853 - 1858
(2007/10/03)
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- Catalyst for use in production of epoxide, method for producing the catalyst, and method for producing epoxide
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To provide an epoxide-production-use catalyst that is suitably used for producing an epoxide by partial oxidation of an unsaturated hydrocarbon, a catalyst in accordance with the present invention is obtained by fixing gold fine particles to a carrier containing an oxide containing at least one of titanium and zirconium, and has an acid quantity of not more than 0.1 mmol/g determined by the NH3-TPD method. Such a catalyst for epoxide producing use can be produced by, for instance, fixing gold fine particles to a carrier having an acid quantity of not more than 0.15 mmol/g. The catalyst for epoxide producing use arranged as above is preferably used as a catalyst in partial oxidation of an unsaturated hydrocarbon to produce a corresponding epoxide.
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- A study of the gas-phase reactivity of neutral alkoxy radicals by mass spectrometry: α-Cleavages and Barton-type hydrogen migrations
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The reactivity of neutral alkoxy radicals in the absence of any interfering intermolecular interactions is investigated by means of the recently introduced method of neutral and ion decomposition difference (NIDD) spectra. These are obtained from quantitative analysis of the corresponding neutralization - reionization (NR) and charge reversal (CR) mass spectra. The following trends emerge: alkoxy radicals with short (C1-C3) or branched alkyl chains give rise to α-cleavage products, whereas longer-chained alkoxy radicals undergo 1,5-hydrogen migrations from carbon to oxygen, that is, Barton-type chemistry. This facile rearrangement has been studied in detail for n-pentoxy radicals by isotopic labeling experiments and computation at the Becke 3LYP/6-31G* level of theory. Further, the NIDD spectra of 3-methylpentoxy radicals permit for the first time the identification of the diastereoselectivity of the gas-phase hydrogen migrations. The results from the NIDD method are compared to those from earlier studies in the condensed phase. This new mass spectrometric approach is suggested as a tool for the examination of intramolecular reactions of free alkoxy radicals which can usefully complement theoretical studies.
- Hornung, Georg,Schalley, Christoph A.,Dieterle, Martin,Schroeder, Detlef,Schwarz, Helmut
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p. 1866 - 1883
(2007/10/03)
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- Regio- and stereoselectivity of particulate methane monooxygenase from Methylococcus capsulatus (Bath)
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The regiospecificity and stereoselectivity of alkane hydroxylation and alkene epoxidation by the particulate methane monooxygenase from Methylcoccus capsulatus (Bath) was evaluated over a range of substrates. Oxidation products were identified by conventional GC analysis, and the stereoselectivity of oxidation was determined by a combination of chiral GC and HPLC methods, as well as 1H NMR analysis of the corresponding (R)-2-acetoxy-2-phenylethanoate ester derivatives in the case of alkanol products. Alkane hydroxylation was found to proceed favoring attack at the C-2 position in all cases, and the stereoselectivity for n-butane and n-pentane was characterized by an enantiomeric excess of 46% and 80%, respectively, with preference for the (R)-alcohol noted for both substrates. Epoxides were formed with smaller stereoselectivities. Together, the regio- and stereoselectivity results suggest that an equilibrium of competing substrate binding modes exists. A simple substrate-binding model that incorporates preferential C-2 oxidation with the observed stereoselectivity of alkane hydroxylation is proposed, and hypotheses for the general mechanism are suggested and discussed.
- Elliott, Scan J.,Zhu, Mei,Tso, Luke,Nguyen, H.-Hoa T.,Yip, John H.-K.,Chan, Sunney I.
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p. 9949 - 9955
(2007/10/03)
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- Steric and stereoelectronic control of the mode selectivity as a function of alkene structure in the reaction with dimethyl α-peroxy lactone: Cycloadducts and ene products versus epoxides
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The oxidation of di-, tri-, and tetrasubstituted alkenes 2 by dimethyl α-peroxy lactone (1) affords the cycloaddition, ene, and epoxidation products 3-6. In the presence of methanol, additionally the trapping products 7 are obtained. The observed dichotomy in the product distribution requires two different paths for this reaction, namely a path via an open, stretched 1,6 dipole and another path for epoxidation. Both paths arise from an SN2 attack of the double bond of the alkene 2 on the peroxide bond of the α-peroxy lactone 1, the first unsymmetrical (end-on attack), leading to the 1,6 dipole A, and the second symmetrical (central attack) with respect to the approach of the double bond, leading to epoxidation. The 1,6 dipole is postulated to afford the cycloadducts, of which the thermodynamically favored diastereomers are obtained, and the ene products. In the epoxidation, the α-lactone released after oxygen transfer oligomerizes to the polyester 8 or in the presence of methanol is trapped as α-methoxy acid 9. The reaction is regioselective both with respect to the attacked oxygen atom of the α-peroxy lactone 1, as revealed by the trapping products 7, as well as with respect to the attacking carbon atom for unsymmetrical alkenes 2c,d, as displayed by the ene products 5 and 6. The former regioselectivity is dictated by the inherent polarization of the peroxide bond through the carbonyl group which makes the alkoxy oxygen the more electrophilic one toward nucleophilic attack, while for the latter the incipient positive charge of the open 1,6 dipole is better stabilized by the more substituted carbon atom of the end-on attacking unsymmetrical alkene. The preferred reaction mode has been found to be sensitive to the structure of the alkene and the difference in reactivity has been explained in terms of steric and stereoelectronic factors. Thus, for the sterically less hindered cis-di- and trisubstitued alkenes the path along the open 1,6 dipole is favored (stereoelectronic control), while the more sterically demanding trans-di- and tetrasubstituted alkenes react by the epoxidation mode (steric control).
- Adam, Waldemar,Blancafort, Lluis
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p. 4778 - 4787
(2007/10/03)
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- Isomerization and Decomposition of 2,3-Dimethyloxirane. Studies with a Single-Pulse Shock Tube
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The isomerizations and decompositions of cis- and trans-2,3-dimethyloxirane were studied behind reflected shocks in a pressurized driver single-pulse shock tube over the temperature range 900-1150 K and overall densities of ca. 3*1E-5 mol/cm3.In addition to a cis trans structural isomerization, four isomerization products, methyl ethyl ketone, isobutyraldehyde, ethyl vinyl ether, and 2-butene-3-ol, were obtained under shock heating.A large number of decomposition products were also obtained.The major ones in decreasing order of abundance were CO, C2H4, C2H6, and CH4.In a similar manner to the decomposition of oxirane and methyloxirane, the free-radical reactions in the present system are initiated by a direct decomposition of a thermally excited methyl ethyl ketone which is produced in the course of the isomerization.A reaction scheme composed of 41 species and 65 elementary reactions accounts for the product distribution over the entire temperature range of this investigation provided decomposition channels of thermally excited isomers are included in the scheme.The rate constants obtained for the isomerization reactions are in good agreement with the values extrapolated from low temperatures.First-order Arrhenius rate parameters for the formation of the various reaction products are given and a sensitivity analysis for their production is summarized.
- Lifshitz, Assa,Tamburu, Carmen
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p. 10251 - 10260
(2007/10/02)
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- 8-HYDROXY-SUBSTITUTED ISOCOUMARINS BY LITHIATION OF BENZENE DERIVATIVES PROMOTED BY β-FUNCTIONALISED ALKYL GROUPS. A REGIOSELECTIVE AND SIMPLE SYNTHESIS OF OOSPOLACTONE
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3-(3-hydroxyphenyl)-2-butanone (obtained in 3 steps from 3-bromophenol and 3-chloro-2-butanone) was ketalised with ethylene glycol and protected at the phenolic OH as the methoxymethyl ether.The intermediate diacetal thus obtained underwent hydrogen-metal exchange with n-butyllithium; the metallated intermediate, after carbonation, methanolysis of acetal groups and elimination of methanol, regioselectively afforded the title compound (8-hydroxy-3,4-dimethylisocoumarin).
- Ramacciotti, Alessio,Fiaschi, Rita,Napolitano, Elio
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p. 111 - 114
(2007/10/02)
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- Purification and Characterization of the Alkene Monooxygenase from Nocardia corallina B-276
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Alkene monooxygenase from the propene utilizer Nocardia corallina B-276 was separated into three components, and all components were purified to homogeneity and their properties were examined.The epoxidase, with a molecular mass of 95 kDa, was considered to catalyze the oxidation of the substrate propene to propylene oxide.It consisted of 53- and 35-kDa subunits, which contained approximately 2-mol of non-heme iron per mole of protein.The reductase, molecular mass 40 kDa, was found to contain an FAD and an Fe2O2 cluster.A third protein, which we have called the coupling protein, with a mass of 14 kDa, appears to function as a regulator of activity.The purified Amo system required NADH as an electron donor, and catalyzed alkene epoxidation only.Acetylene, a specific inhibitor for methane monooxygenase, did not inhibit the AMO activity.
- Miura, Akira,Dalton, Howard
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p. 853 - 859
(2007/10/02)
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- Epoxide formation in the reactions of the nitrate radical with 2,3-dimethyl-2-butene, cis- and trans-2-butene and isoprene
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Epoxide formation in the nighttime reaction of NO3 with 2,3-dimethyl-2-butene, cis- or trans-2-butene or isoprene was studied in a 480 l reaction chamber with in situ FTIR spectroscopy as analytical technique. Most experiments were carried out at either 20 Torr in argon or at 740 Torr in synthetic air. In the case of 2,3-dimethyl-2-butene the epoxide formation was studied in the range 20-740 Torr using either argon or air as diluent gas and its O2 dependence was studied in N2/O2 mixtures with O2 concentrations in the range 1.7 x 1015-4.9 x 1018 molec cm-3, at a total pressure of 740 Torr. In the experiments performed at 20 Torr in argon, epoxides were found in all reactions as main products. The measured molar yields were 95.3% for 2,3-dimethyl-2-butene, 50% for cis- and trans-2-butene and 20% for isoprene. In the experiments performed at 740 Torr air, epoxides were below the detection limit in the case of cis- and trans-2-butene and isoprene, whereas a yield of 17.4% of the epoxide was measured in the 2,3-dimethyl-2-butene experiments. Possible reaction mechanisms explaining the experimental results are discussed. Epoxide formation in the nighttime reaction of NO3 with 2,3-dimethyl-2-butene, cis- or trans-2-butene or isoprene was studied in a 480 l reaction chamber with in situ FTIR spectroscopy as analytical technique. Most experiments were carried out at either 20 Torr in argon or at 740 Torr in synthetic air. In the case of 2,3-dimethyl-2-butene the epoxide formation was studied in the range 20-740 Torr using either argon or air as diluent gas and its O2 dependence was studied in N2/O2 mixtures with O2 concentrations in the range 1.7 × 1015-4.9 × 1018 molec cm-3, at a total pressure of 740 Torr. In the experiments performed at 20 Torr in argon, epoxides were found in all reactions as main products. The measured molar yields were 95.3% for 2,3-dimethyl-2-butene, 50% for cis- and trans-2-butene and 20% for isoprene. In the experiments performed at 740 Torr air, epoxides were below the detection limit in the case of cis- and trans-2-butene and isoprene, whereas a yield of 17.4% of the epoxide was measured in the 2,3-dimethyl-2-butene experiments. Possible reaction mechanisms explaining the experimental results are discussed.
- Skov,Benter Th.,Schindler,Hjorth,Restelli
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p. 1583 - 1592
(2007/10/03)
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- REMPI-MS and FTIR Study of NO2 and Oxirane Formation in the Reactions of Unsaturated Hydrocarbons with NO3 Radicals
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The yields of NO2 and oxirane have been studied as a function of pressure in the reactions of NO3 with selected unsaturated hydrocarbons.NO2 yields were determined using a flow system with double resonance REMPI-MS technique in the range 1-30 mbar, argon being the buffer gas.The yields of oxiranes were studied using in situ FTIR technique in a static system in the pressure range 30-1000 mbar.With styrene, oxirane formation was also determined by REMPI-MS.The experiments revealed that the NO2 yields decreased strongly with pressure in the case of aliphatic dienes and styrene, whereas only a negligible pressure dependence of NO2 formation was observed with alkenes or cyclic dienes.These results were confirmed for 2,3-dimethyl-2-butene and for isoprene in the FTIR experiments in which the corresponding oxirane yields were measured at up to 1000 mbar of argon.Air as buffer gas reduced oxirane formation.In the reaction of cis-2-butene and trans-2-butene with NO3 similar yields of trans-2,3-dimethyloxirane were obtained.This finding is taken as the most direct evidence for the NO3 radical addition to the carbon double bond in alkenes in the primary reaction step in agreement with previous assumptions.
- Benter, Th.,Liesner, M.,Schindler, R. N.,Skov, H.,Hjorth, J.,Restelli, G.
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p. 10492 - 10496
(2007/10/02)
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- Iron(I)-induced diastereoselective C-H bond activation in nonrigid molecules
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The Fe(I)-mediated introduction of a terminal C - C double bond by gas-phase dehydrogenation of 3-methylpentan-2-one is subject to diastereoselective discrimination of the hydrogen atoms of C(4). This unprecedented effect in gas-phase organometallic chemistry results most likely from the formation of chairlike intermediates bearing an axial or an equatorial methyl substituent, depending on the relative configuration of C(3) in the acyclic substrate. The latter reaction path is favored by a factor of 1.5, and a kinetic isotope effect kH2/kHD = 2.13 is associated with the reductive elimination of molecular hydrogen.
- Schr?der, Detlef,Schwarz, Helmut
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p. 8818 - 8820
(2007/10/02)
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- Reactions Involving Hot O(3P) Atoms and Isomeric 2-Butene
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The low-pressure gas-phase investigation is reported on the reactions involving high-energy O(3P) atoms with cis- and trans-butene.Gas chromatographic analysis of stable hydrocarbon end products revealed a complex spectrum of compounds containing carbonyl, epoxide, and alcohol groups.The large distribution of alcohol products was a distinct feature in these hot atom systems, indicating that OH radical formation was important.These analyses revealed differences in the internal energy levels of the reaction intermediates formed through the greater pressure dependence exhibited by the degree of stereospecific addition of oxygen atoms to trans-butene then reaction with cis-butene and through the greater degree of internal rearrangement and carbon-carbon bond scission exhibited by the trans intermediate.Direct measurements using on-line mass spectrometry also revealed that CO product signals were 14.6 times higher from reactions with cis-butene than with trans-butene, indicating greater reactivity of the cis ?-bond toward oxygen atom attack.Similarly, these direct analyses revealed that OH product signals were 1.7 times higher from reactions with cis-butene, suggesting that in addition to direct H abstraction an indirect pathway involving mutual interaction with the substrate's ?-bond may have contributed, in part, to those OH products observed in these studies.Kinetic energy moderator studies supported this hypothesis through the different moderator dependencies exhibited by the OH product signals seen to arise from high-energy oxygen atom reactions with the two stereoisomers.
- Ferrieri, Richard A.,Wolf, Alfred P.
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p. 4747 - 4752
(2007/10/02)
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- Oxidation Chemistry of Propene in the Autoignition Region: Arrhenius Parameters for the Allyl + O2 Reaction Pathways and Kinetic Data for Initiation Reactions
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The oxidation of propene has been studied at a total pressure of 60 Torr between 400 and 520 deg C, and a detailed product analysis made in the initial stages of reaction over a wide range of mixture composition.Mechanisms for the formation of the products are discussed.The initial rates of formation of hexa-1,5-diene (HDE) and carbon monoxide are used to obtain A8 = 109.66 +/- 0.35 dm3 mol-1 s-1 and E8 = 78.6 +/- 4.5 kJ mol-1, the former giving from the known value of k1 CH2=CHCH2* + CH2=CHCH2* -> CH2=CHCH2CH2CH=CH2 (1).CH2=CHCH2* + O2 -> CO + products.Arrhenius parameters are also given for alternative pathways of the allyl + O2 reaction.All involve high energy barriers.From measurements of the accelerating effect of small amounts of additives CH3CHO, HCHO, HDE and propene oxide, rate constants at 480 deg C are obtained (for the first three) for the initiation reaction (21) RH + O2 -> R + HO2.Very few independent data for this type of reaction are available.The accelerating effect of propene oxide is ascribed to an exothermic isomerisation product which is not thermally stabilised at 60 Torr and undergoes homolysis to radical fragments.HDE is shown to have a spectacular accelerating effect on propene oxidation and values of k21n/k10 = 1050 +/- 200 at 480 deg C is obtained.C3H6 + O2 -> CH2=CHCH2* + H2O.HDE + O2 -> *CH2CH=CHCH2CH=CH2 + H2O.
- Stothard, Nigel D.,Walker, Raymond W.
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p. 2621 - 2630
(2007/10/02)
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- Oxirane Formation in the Reaction of NO3 Radicals with Alkenes
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Chemical Kinetics / Mass Spectrometry / Radicals.Mass spectra of products formed in the reaction between NO3 and cis-2-butene, isobutene, 2-methyl-2-butene and 2,3-dimethyl-2-butene at 298 K and p = 3-10 mbar were obtained, using a fast flow system with molecular beam sampling.The spectra indicate formation of an oxirane in each reaction.Within experimental error the oxirane yields in the reaction of cis-2 butene and of 2,3-dimethyl-2-butene were identical (90+/-10)percent.The rate of oxirane formation was found to obey the rate equation for the reaction: NO3 + alkene oxirane + NO2. (1) Good agreement was obtained for the rate constants of reaction (1) determined from the rate of oxirane formation and those determined in earlier works from the consumption of reactants.
- Wille, U.,Rahman, M. M.,Schindler, R. N.
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p. 833 - 835
(2007/10/02)
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- Stereocontrolled Oxazolidinone Formation by the Addition of 4,5-Disubstituted Iminodioxolane to Oxirane via a Spiro Compound
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4,5-Disubstituted 2-imino-1,3-dioxolanes readily add to oxiranes in the presence of AlCl3, furnishing 1,3-oxazolidin-2-ones in a stereospecific manner, where the configurations of oxiranes and iminodioxolanes are responsible for the configuration of products and the feasibility of the addition, respectively.A preliminary adduct, a spiro compound intermediate, is isolated, and its decomposition to oxazolidinone is demonstrated.
- Baba, Akio,Seki, Kenji,Matsuda, Haruo
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p. 2684 - 2688
(2007/10/02)
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- The Synthesis of Oxiranes and Oxetanes from 1,2- or 1,3-Halohydrins Using Organoantimony(V) Alkoxide
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Tetraphenylstibonium methoxide (1) is an effictive reagent for the synthesis of oxiranes and oxetanes from the corresponding 1,2- and 1,3-halohydrins, respectively.As the reaction conditions are neutral, oxiranes bearing an ester moiety were obtained intact without undergoing solvolysis.In addition, oxetanes, whose preparation was not generally facile, were formed in good yields under mild conditions (60-80 deg C).
- Fujiwara, Masahiro,Hitomi, Kazuhisa,Baba, Akio,Matsuda, Haruo
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p. 106 - 109
(2007/10/02)
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- Arrhenius Parameter for the Addition of HO2 Radicals to (E)-But-2-ene over the Range 400 - 520 deg C
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Studies have been made of the addition of HO2 radicals to (E)-but-2-ene in the temperature range 400 - 520 deg C, by use of the co-oxidation of (E)-but-2-ene and propene in the presence of tetramethylbutane as a source of HO2 radicals.From measurements of the relative yields of 2,3-dimethyloxirane and methyloxirane and the known Arrhenius parameters for reaction (6), values of A7 = 108.61 +/- 0.30 dm3 mol-1 s-1 and E7 = 50.0 +/- 4 kJ mol-1 have been obtained. .The values are compared with data for HO2 addition to other alkenes.The excellent correlation between the activation energy for addition and the ionisation energy of the alkene is used to provide a kinetic data base for HO2 addition to alkenes over the range 600-1000 K, where the reactions are of major importance.From studies of the relative yields of 2,3-dimethyloxirane and (Z)-but-2-ene from (E)-but-2-ene + H2 + O2 mixtures, further evidence is presented to show that the decomposition of hydroperoxyalkyl radicals, such as CH3CH(OOH)CHCH3, into alkene + HO2 is at most a minor process compared with formation of an oxirane + OH radical.
- Stothard, Nigel D.,Walker, Raymond W.
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p. 2115 - 2119
(2007/10/02)
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- Stopped-Flow Studies of the Mechanisms of Ozone-Alkene Reactions in the Gas Phase: trans-2-Butene
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The reaction of ozone with trans-2-butene has been studied in the gas phase at 294 K and 530 Pa (4 Torr) by using a stopped-flow reactor coupled to a photoionization mass spectrometer.The concentrations of reactants and products were determined as a function of reaction time.A mechanism is proposed to account for the observed products: CH3CHO, H2CO, CO2, CH4, CF3C(O)C(H)(OH)CH3, H2C=C=O, H2O, 2-butanone, 2,3-epoxybutane, CH3C(O)C(O)CH3, and HC(O)C(O)H.This work again indicates that simple "hot" ester hypothesis needs to be critically reconsidered for gas-phase ozonolysis.
- Martinez, Richard I.,Herron, John T.
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p. 4644 - 4648
(2007/10/02)
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- USING THE COMPARISON OF STERIC VERSUS ELECTRONIC EFFECTS TO INFER MECHANISTIC INFORMATION IN STEPWISE ELECTROPHILIC ADDITION REACTIONS INVOLVING THREE-MEMBERED CYCLIC INTERMEDIATES
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Correlations of IP's versus relative reactivities or formation constants of reactions of alkenes with ArSCl, MeCO3H, Ag(1+), or HgCl2 reveal that complexation reactions show steric dependence, that additions with the first step rate-determining are sterically independent, and that those with the second step rate-determining are sterically dependent.
- Nelson, Donna J.,Soundararajan, Raman
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p. 6207 - 6210
(2007/10/02)
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- Selective Epoxidation of Olefins by Oxo(V) Alkylpreoxides. On the Mechanism of the Halcon Epoxidation Process
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Novel vanadium(V) alkylperoxy complexes with the general formula VO(OOR)(R'-OPhsal-R'') (II) were synthesized and characterized by physicochemical methods.These complexes most probably have a pentagonal pyramidal structure, with an axial vanadyl group and, in the pentagonal plane, three positions occupied by the Schiff base planar ligand and two positions occupied by a bidendate alkylperoxy group which is presumably weakly coordinatively bonded to the metal by the alkoxy oxygen atom.These complexes are very effective reagents for the selective transformation of olefins into epoxides, with yields ranging from 40percent for 1-octene to 98percent for tetramethylethylene.The reactivity of olefins is sensitive to steric hindrance and increases with the olefin nucleophilicity.The epoxidation of olefins by complexes II is steroselective, inhibited by water, alcohols, and basic ligands or solvents, and accelerated in polar nondonor solvents.Kinetic studies showed that the olefin coordinates to the metal prior to the decomposition of the metal-olefin complex in the rate-determining step.Competitive epoxidation of several olefins vs. cyclohexene showed that the more strongly coordinated olefins exert an inhibiting effect on the epoxidation of the less strongly coordinated ones.These data, which are similar to those of the Halcon catalytic epoxidation process, are consistent with a pseudocyclic peroxy metalation mechanism.
- Mimoun, Hubert,Mignard, Michel,Brechot, Philippe,Saussine, Lucien
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p. 3711 - 3718
(2007/10/02)
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- CHIMIE ORGANOMETALLIQUE SOUS HAUTE PRESSION: REACTION DES CHLOROCETONES AVEC L'HYDRURE DE TRIBUTYLETAIN
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High-pressure reaction of tributyltin hydride with several chloroketones (3-chloro-2-butanone, 4-chloro-2-butanone, 5-chloro-2-pentanone, 6-chloro-2-hexanone and 7-chloro-2-heptanone) led to the formation of chloroalkoxytins or cyclic ethers.An ionic mechanism, starting with nucleophilic attack at the carbonyl group, is proposed to explain the formation of the reaction products.
- Degueil-Castaing, M.,Maillard, B.,Rahm, A.
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- EPOXIDATION OF 2-BUTENE BY ORGANIC HYDROPEROXIDES.
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The authors report the results of a study of epoxidation of 2-butene by organic hydroperoxides ( alpha -methylbenzyl, alpha , alpha -dimethylbenzyl, and tert-butyl) in presence of hydrocarbon-soluble molybdenum compounds. Alkylbenzenes (toluene, ethylbenzene, and isopropylbenzene) were used as solvents. It is shown that a comparison of the reactions of 2-butene epoxidation by various organic hydroperoxides ( alpha -methylbenzyl, alpha , alpha -dimethylbenzyl, and tert-butyl) shows that under the given conditions approximately equal degrees of conversion of these hydroperoxides are attained, i. e. , they are virtually equal in activity, while selectivity for 2-butene oxide formation is somewhat lower when alpha , alpha -dimethylbenzyl hydroperoxide is used.
- Farberov,Bondarenko,Obukhov,Srednev,Vasil'eva
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p. 134 - 138
(2007/10/02)
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- Evidence for molecular complexes in the mechanism of additions of iodine monochloride to alkenes
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Immediately upon mixing ICl and 2,3-dimethyl-2-butene in CCl4 at 25 deg C a new absorption band due to an alkene - ICl molecular complex appears at 295 +/- 5 nm and decreases rapidly with time.The rate law under conditions of (alkene)0 >> (ICl)0/dt = kexpt(alkene)(ICl)3/AD(alkene)>3 where KAD is the equilibrium constant for the formation of a 1:1 alkene - ICl molecular complex.The addition of ICl to the Z and E isomers of 2-butene and 1-phenylpropene occurs by anti-stereospecific addition.The negative enthalpy of activation for the addition of ICl to 2,3-dimethyl-2-butene is evidence that one or more complexes are involved on the reaction coordinate prior to the rate-determining step.On the basis of analysis of the enthalpy changes during the reaction, it is proposed that both a 1:1 and a 1:2 alkene - ICl molecular complex is involved in the mechanism prior to the rate-determining step.
- Schmid, George H.,Gordon, James W.
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p. 2526 - 2534
(2007/10/02)
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- RATE CONSTANTS FOR THE FORMATION OF OXIRANES BY γ-SCISSION IN SECONDARY β-t-BUTYLPEROXYALKYL RADICALS
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Rate constants for the title reactions have been determined from the ratios of oxirane to peroxide obtained in the reductons of β-bromoalkyl t-butyl peroxides with tributyltin hydride.At ca. 298 K the rate constants are 0.32, 1.12, 1.96, 2.0 and 6.2E6 s-1 for β-t-butylperoxy derivatives of trinorbornan-2-yl (exo) cyclohexyl, 1-methylpropyl , cyclopentyl and 1-ethylbutyl, respectively.The results are discussed in terms of steric and electronic effects in the transition state leading to ring closure of the radicals.
- Bloodworth A. J.,Courtneidge, J. L.,Davies, Alwyn G.
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p. 523 - 528
(2007/10/02)
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- VANADIUM(V) PEROXO COMPLEXES. NEW VERSATILE BIOMIMETIC REAGENTS FOR EXPOXIDATION OF OLEFINS AND HYDROXYLATION OF ALKANES AND AROMATIC HYDROCARBONS.
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Novel covalent vandium(V) oxo peroxo complexes of general formula VO(O//2)(O-N)LL prime and anionic complexes with the general formula left bracket VO(O//2)(Pic)//2 right bracket ** minus A** plus L were synthesized and characterized by physicochemical methods and X-ray crystallography. The crystal structure of VO(O//2)(Pic) multiplied by (times) 2H//2O (Ia) revealed a pentagonal-bipyramidal environment, with a significant hydrogen bonding between the peroxo moiety and the equatorial water molecule. Protonated type II complexes (A** plus equals H** plus ) are dissociated in an aqueous solution and have an acidic nature (pK//a equals 1. 8) but are undissociated in a nonprotic solution, with a presumably peracid-like oxohydroperoxo structure. It is shown that vanadium peroxo complexes are effective oxidants in nonprotic solvents under mild conditions. They transform olefins to epoxides and cleavage products in a nonsteoroselective fashion (cis-2-butene gave a mixture of cis and trans epoxides). More interestingly, they hydroxylate aromatic hydrocarbons to phenols and alkanes to alcohols and ketones.
- Mimoun,Saussine,Daire,Postel,Fischer,Weiss
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p. 3101 - 3110
(2007/12/18)
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- EPOXIDATION REACTIONS CATALYZED BY IRON PORPHYRINS. OXYGEN TRANSFER FROM IODOSYLBENZENE.
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The epoxidation of olefins by iodosylbenzene is catalyzed by synthetic iron porphyrins. With (chloro-5, 10, 15, 20 -tetraphenylporphyrinato) iron(III) (FeTPPCl), cyclohexadiene oxide was produced in 93% yield and with (chloro-5, 10, 15, 20-tetra-o-tolyporphyrinato) iron (III) (FeTTPCl), cycloctene oxide was produced in 84% yield. Cis olefins were found to be more reactive than trans olefins. Thus, whereas cis-stilbene was epoxidized by FeTPPCl/iodosylbenzene in 77% yield, trans-stilbene was unreactive under these conditions. The degree of cis/trans selectivity was a sensitive function of substitution of the porphyrin periphery. With (chloro-5, 10, 15, 20-tetramesitylporphyrinato)iron(III), the relative reactivity of cis-and trans-cyclododecene was 8. 92:1. Similarly, the less reactive cis double bond of trans, trans, cis-cyclododecatriene could be selectively epoxidized by this catalyst. Trans 1,2-disubstituted double bonds showed similar reactivities. These results suggest an approach of the double bond from the side of iron-bound oxygen and parallel to the prophyrin plane. A mechanism involving formation of an oxygen transfer from a reactive iron-oxo intermediate is proposed for this reaction.
- Groves,Nemo
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p. 5786 - 5791
(2007/10/02)
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- Oxymetallation. Part 16. Modified Procedures for Reducing Peroxymercurials: Conversion of Non-terminal Alkenes into Secondary Alkyl t-Butyl Peroxides
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Various procedures for reducing PhCH(OOBut)CH2HgO2CCF3 or PhCMe(OOBut) have been investigated in an attempt to optimize yields of the mercury-free peroxides.Effects of varying the concentration of borohydride and the mode of mixing, and of including a phase transfer catalyst, have been assessed for the two phase system of alkaline NaBH4 and dichloromethane and reductions have been carried out in a single phase by using Bu4NBH4 in dichloromethane.The t-butyl peroxymercurials t)CH(HgX)R> derived from cis- and trans-but-2-ene, cis- and trans-hex-3-ene, cyclopentene, cyclohexene, and norbornene have been reduced under the optimum conditions of slowly adding base-pretreated peroxymercurials in dichloromethane to a large excess of alkaline NaBH4.Product analyses support the idea that the reactions proceed via β-peroxyalkyl radicals t)CHR>, but show that, except for the norbornyl derivative, epoxides are the dominant products; cyclopentyl, cyclohexyl, and exo-norbornyl t-butyl peroxides have been isolated in yields of 2, 13, and 37 percent, respectively.Better, but still modest, yields (24-36 percent) have been obtained for butan-2-yl, hexan-3-yl, and cyclopentyl t-butyl peroxides by silver trifluoroacetate-assisted t-butyl perhydrolysis of the alkyl bromides, but competing dehydrobromination lowered the yield (6 percent) of the cyclohexyl compound.Vastly improved yields (ca. 60 percent) of butan-2-yl, cyclopentyl, and cyclohexyl t-butyl peroxides have been achieved by reduction of the corresponding peroxymercurials with neat Bu3SnH.
- Bloodworth, A. J.,Courtneidge, J. L.
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p. 1797 - 1806
(2007/10/02)
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- A FACILE METHOD FOR OXYTELLURATION OF OLEFINS
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Treatment of olefins with phenyltellurium(II) or (IV) species in alcohol at room to reflux temperature for 1-24 h produces the corresponding (2-alkoxyalkyl)phenyltellurium dihalides in good yields, the reaction being trans-stereoselective and highly regioselective.
- Uemura, Sakae,Fukuzawa, Shin-ichi,Toshimitsu, Akio,Okano, Masaya
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p. 1177 - 1180
(2007/10/02)
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- Gas-Phase Acid-Induced Nucleophilic Displacement Reactions. 5. Quantitative Evaluation of Neighboring-Group Participation in Bifunctional Compounds
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A previous radiolytic study on the stereochemistry of gas-phase nuclephilic displacement on several classes of positively charged intermediates, formed from the attack of gaseous acids (CH5+, C2H5+, CH3FCH3+, etc.) on suitable substrates, is now completed with the assessment of the detailed mechanism and the relative extent of the other major reaction pathways accompanying them.The analysis of the stereoisomeric distribution of the neutral end products allows a quantitative evaluation of the gas-phase neighboring-group participation in such systems.A participating-group ability trend of OH >> Br >/= Cl is found, which is appreciably dependent on the nature of the leaving group and the configuration of the starting substrate.The evaluation of the adjacent-group "effective concentration" in these gaseous systems provides the first direct evidence for a gas-phase anchimerically assisted ionic reaction, involving a three-membered ring formation.The results obtained in the gas phase differ significantly from those concerning related solvolytic processes.
- Angelini, Giancarlo,Speranza, Maurizio
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p. 3800 - 3806
(2007/10/02)
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- The Mechanism of Ozone-Alkene Reactions in the Gas Phase. A Mass Spectrometric Study of the Reactions of Eight Linear and Branched-Chain Alkenes
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The stable products of the low-pressure (4 - 8 torr (1 torr = 133.33 Pa)) gas-phase reactions of ozone with ethene, propene, 2-methylpropene, cis-2-butene, trans-2-butene, trans-2-pentene, 2,3-dimethyl-2-butene, and 2-ethyl-1-butene have been identified by using a photoionization mass spectrometer coupled to a stirred-flow reactor.The products observed are characteristic of (i) a primary Criegee split to an oxoalkane (aldehyde or ketone) and a Criegee intermediate, (ii) reactions of the Criegee intermediates such as unimolecular decomposition, secondary ozonide formation, etc., and (iii) secondary alkene chemistry involving OH and other free-radical products formed by the unimolecular decomposition of the Criegee intermediates.The secondary OH - alkene - O2 reactions account for a significant fraction of the alkene (CnH2n) consumed and lead to characteristic products such as Cn dioxoalkanes nH2n + 30)>, Cn acyloins nH2n + 32)>, and Cn alkanediols nH2n + 34)>.Cn oxoalkanes and Cn epoxyalkanes observed at m/e (CnH2n + 16) are probably formed primarily via epoxidation of the alkene by O3.A general mechanism has been proposed to account for the observations.
- Martinez, Richard I.,Herron, John T.,Huie, Robert E.
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p. 3807 - 3820
(2007/10/02)
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- Oxygenation with Molecular Oxygen. Thermal and Photochemical Epoxidation of Propylene in the Presence of Sulfur Dioxide in Acetonitrile at Ambient Temperature
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Irradiation of a mixture of propylene and sulfur dioxide in acetonitrile at ice-cold temperature causes absorption of molecular oxygen and gives propylene oxide as the sole volatile product.Also, in the absence of light, the addition of nitrile or nitrate salts to a mixture of sulfur dioxide and propylene in acetonitrile under oxygen at room temperature leads to the smooth formation of propylene oxide as the only volatile product.Both reactions show quite similar solvent dependence and are retarded by the additives with ionization potentials lower than ca. 9.5 eV.The main byproduct is poly(propylenesulfonate).The mechanisms of the epoxidation reactions are discussed.
- Sasaki, Tadahiro
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p. 3882 - 3886
(2007/10/02)
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- Gas-Phase Acid-Induced Nucleophilic Displacement Reactions. Stereochemistry of Inter- and Intramolecular Substitutions at Saturated Carbon
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The stereochemistry of gas-phase nucleophilic displacement by water on a number of positively charged intermediates was investigated under different experimental conditions.The ionic intermediates were generated in the gas phase at atmospheric pressure by attack of radiolytically formed Broensted (CH5+, C2H5+) and Lewis (C2H5+, CH3FCH3+) acids on selected mono- and bifunctional substrates.Isolation and identification of their neutral substituted products allowed us to demonstrate that, under the used experimental conditions, gas-phase acid-induced inter- and intramolecular nucleophilic displacement reactions occur via predominant (64-98percent) inversion of configuration at the reaction center.The yield and the stereoisomeric distribution of the substituted products were found to depend on either the nature of the gaseous acid used to generate the charged intermediates or the concentration of the added base (NH3 or H2O).Product distribution from bifunctional substrates is characterized by the presence of minor amounts of substituted derivatives retaining the original configuration of their neutral precursors.Their formation is ascribed to the occurence of an extensive neighboring group participation effect (an HO-3 process) on the displacement reaction, resulting in a double inversion of the reaction centers.A mechanistic model is proposed for gas-phase nucleophilic substitutions at atmospheric pressures, and compared with those from the related low-pressure ICR (ion cyclotrone resonance mass spectrometry) and solution-chemistry studies.
- Speranza, Maurizio,Angelini, Giancarlo
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p. 3115 - 3120
(2007/10/02)
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- Linear-reactor-infrared-matrix and Microwave Spectroscopy of the cis-2-Butene Gas-phase Ozonolysis
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Investigation of the formation of complex products in the gas-phase ozonolysis of cis-2-butene by linear-reactor-infrared-matrix and linear-reactor-microwave spectroscopy is reported.The following species have been unequivocally detected: secondary 2-butene ozonide, acetic acid, peracetic acid, glycolaldehyde, dimethyl ketene, the simple mixed anhydrides of formic and acetic acid, 2,3-epoxy-butane and 2-butanone, besides polyatomic products alredy known.In contrast, the primery ozonide has been detectable neither by LR.-MW. nor by LR.-IR.Observation of both stereoisomeric epoxides and kinetic modelling are used to support the intermediate formation of the O'Neal-Blumstein radical CH3CH(O2)CH(O)CH3 and the existence of a reaction channel in which the two carbon atoms of the C,C double bond of the olefin remain connected.As the dominant reaction path a mechanism with a Criegee type split into methyldioxirane (ethylidene peroxide) and acetaldehyde is considered and subsequently proposed to explain formation of many complex products by either unimolecular or bimolecular processes of the peroxide.For the reactions considered, thermochemical estimates of reaction enthalpies and activation data are included.Kinetic modelling for a partial reaction mechanism involving at least two different paths of decay of the O'Neal-Blumstein biradical into Criegee-type intermediates and the 2,3-epoxy-butanes is discussed.
- Kuehne, Heinz,Forster, Martin,Hulliger, Juerg,Ruprecht, Heidi,Bauder, Alfred,Guenthard, Hans-Heinrich
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p. 1971 - 1999
(2007/10/02)
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- ETUDE ANALYTIQUE DE LA REACTION D'OXYDATION DE BASSE TEMPERATURE DU BUTANE EN PRESENCE DE METHYLAMINES
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Studied by static method the reaction is followed by measuring the derivative of the pressure variations as a function of time and by analysis of methanol, ethanol, acetone, nitromethane, 2,3 epoxy butane, 1,2 epoxy butane, butanone, 2-butanol and carbon oxide and dioxide by gas-chromatography.The methylamines are analysed by colorimetry through pH measurements.The analyses are mainly performed in the slow branched-chains reaction zone and followed as a function of the butane concentration and for increasing amounts of each of the three additives.A relevant explanation of the nitromethane formation in presence of methylamines enable us to enlighten some interesting features of the reaction mechanism.
- Lemahieu Joseph,Antonic, Stanislas
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p. 337 - 342
(2007/10/02)
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- Process for preparing aldehydes from oxirane compounds
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Aldehydes are prepared by reacting an oxirane compound with hydrogen peroxide in the presence of a boron compound.
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2-Halogenoalkoxytributyltin compounds have been prepared from tributylethoxytin and 1,2-halohydrins. The thermal degradation and its mechanism are investigated. These reactions offer a convenient way to prepare epoxides.
- Delmond, Bernard,Pommier, Jean-Claude,Valade, Jacques
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