925669-95-0Relevant articles and documents
REMPI-MS and FTIR Study of NO2 and Oxirane Formation in the Reactions of Unsaturated Hydrocarbons with NO3 Radicals
Benter, Th.,Liesner, M.,Schindler, R. N.,Skov, H.,Hjorth, J.,Restelli, G.
, p. 10492 - 10496 (1994)
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.
Gas-phase dehydration of vicinal diols to epoxides: Dehydrative epoxidation over a Cs/SiO2 catalyst
Kim, Tae Yong,Baek, Jayeon,Song, Chyan Kyung,Yun, Yang Sik,Park, Dae Sung,Kim, Wooyoung,Han, Jeong Woo,Yi, Jongheop
, p. 85 - 99 (2015/09/28)
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.
Isomerization and Decomposition of 2,3-Dimethyloxirane. Studies with a Single-Pulse Shock Tube
Lifshitz, Assa,Tamburu, Carmen
, p. 10251 - 10260 (2007/10/02)
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.
Epoxide formation in the reactions of the nitrate radical with 2,3-dimethyl-2-butene, cis- and trans-2-butene and isoprene
Skov,Benter Th.,Schindler,Hjorth,Restelli
, p. 1583 - 1592 (2007/10/03)
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.
Stereocontrol of the Red Light Induced Photoepoxidation of 2-Butenes by Nitrogren Dioxide in Solide Ar
Nakata, Munetaka,Frei, Heinz
, p. 7670 - 7677 (2007/10/02)
Photooxidation of cis-2-butene was initiated in an inerrt gas matrix by exciting cis-2-butene*NO2 pairs at red, yellow, and green wavelengths .Chemical reaction was monitored by FT-IR spectroscopy, and emission from an Ar ion or a tuned CW dye laser was used for photolysis.As in the case of the trans-2-butene + NO2 reaction reported earlier, 2,3-epoxybutane was the only final oxidation product observed upon direct photolysis of reactant pairs.While in the case of the trans-2-butene reaction stereochemical retention was complete, we found in the cis case 85percent of the epoxide with retained configuration when conducting the reaction at low matrix concentration.This fraction decreased with increasing reactant to matrix ratio.Infrared bands of two conformers of a butyl nitrile radical were observed concurrently with the epoxide, one syn, the other anti with respect to conformation (CH3 groups) about the central CC bond.A correlation was found between the syn to anti nitrile radical and the cis to trans epoxide ratios, suggesting a common transient precursor.It is most probably an oxirane biradical, whose conformation determines the stereochemistry of the epoxide product.The photolysis wavelength dependence of the product growth kinetics was studied, and relative reaction efficiencies so obtained are shown to give insight into aspects of the dynamics of the reaction that relate to the observed product and stereospecificity.The two trapped butyl nitrite radical conformers were found to photodissociate under exposure to long-wavelength visible light with complete conformer specificity.The anti conformer gave trans-2-butene oxide and NO at a threshold wavelength of 613 nm, while the syn form was found to decompose to 2-methylpropanal and NO upon 573 nm and shoter wavelength irradiation.
Oxygen Donation by an Intermadiate in the Reaction of 3CF2 with O2
Rahman, M.,McKee, Michael L.,Shevlin, Philip B.,Sztyrbicka, Renata
, p. 4002 - 4007 (2007/10/02)
Reaction of 3CF2, produced by reaction of arc-generated carbon atoms with CF3, with oxygen in the presence of alkenes oxygenates to epoxides, which are formed stereospecifically, and carbonyl compounds.The reaction is postulated to involve the intermediacy of difluorodioxirane, which transfers oxygen stereospecifically to the alkene.Ab inito calculations demonstrate that the difluorodioxirane is more stable than the corresponding carbonyl oxide to the dioxirane should be rapid.The results of these calculations are compared to those on the parent CH2O2 system.Reaction of carbon atoms with oxigen and alkenes in the absence of CF3 gives nonstereospecific epoxidation presumably through the intermediacy of O atoms.
Diethoxytriphenylphosphorane: A Mild, Regioselective Cyclodehydrating Reagent for Conversion of Diols to Cyclic Ethers. Stereochemistry, Synthetic Utility, and Scope
Robinson, Philip L.,Barry, Carey N.,Kelly, Jeffery W.,Evans, Slayton A.
, p. 5210 - 5219 (2007/10/02)
Diethoxytriphenylphosphorane, Ph3P(OEt)2, prepared by reaction of triphenylphosphine and diethyl peroxide, is a "hydrolytically active" dioxyphosphorane which promotes mild cyclodehydration (40-110 deg C) of diols to cyclic ethers in neutral media.The regioselectivity in the closure of (S)-(+)-propane-1,2-diol and (R)-(-)-pentane-1,4-diol with Ph3P(OEt)2 is high (81-82 percent) while the cyclodehydration of (S)-(+)-phenylethane-1,2-diol gives racemized (+/-)-styrene oxide.Simple 1,2-, 1,4-, and 1,5-diols afford good yields of the cyclic ethers but 1,3-propanediol and 1,6-hexanediol give mainly 3-ethoxy-1-propanol and 6-ethoxy-1-hexanol, respectively with Ph3P(OEt)2.Tri- and tetra-substituted 1,2-diols afford the relatively stable 1,3,2-dioxaphospholanes (or ?-dioxyphosphoranes) in the presence of Ph3P(OEt)2, and, depending on conditions, the 1,3,2-dioxaphospholanes are selectively converted to epoxides, ketones or allylic alcohols.The carbonyl compounds arise from 1,2-hydride and 1,2-methyl migrations; the allylic alcohols are derived from thermolytic eliminations. trans-1,2-Cyclohexanediols afford essentially quantitative yields (>95 percent) of the cyclohexene oxides while cis-1,2-cyclohexanediol gives the stable 1,3,2-dioxaphospholane with Ph3P(OEt)2 which decomposes under thermal conditions to cyclohexanone (90 percent).Ph3P(OEt)2 is extremely useful for conversion of "sensitive" 1,2-diols to acidic and /or thermally labile epoxides as demonstrated by the quantitative conversion of 9,10-dihydro-trans-9,10-phenanthrenediol to 9,10-dihydrophenanthrene oxide and 2α,10-pinanediol to 2α,10-epoxypinane.
CHIMIE ORGANOMETALLIQUE SOUS HAUTE PRESSION: REACTION DES CHLOROCETONES AVEC L'HYDRURE DE TRIBUTYLETAIN
Degueil-Castaing, M.,Maillard, B.,Rahm, A.
, p. 49 - 56 (2007/10/02)
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.
VANADIUM(V) PEROXO COMPLEXES. NEW VERSATILE BIOMIMETIC REAGENTS FOR EXPOXIDATION OF OLEFINS AND HYDROXYLATION OF ALKANES AND AROMATIC HYDROCARBONS.
Mimoun,Saussine,Daire,Postel,Fischer,Weiss
, p. 3101 - 3110 (2007/12/18)
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.
EPOXIDATION REACTIONS CATALYZED BY IRON PORPHYRINS. OXYGEN TRANSFER FROM IODOSYLBENZENE.
Groves,Nemo
, p. 5786 - 5791 (2007/10/02)
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.
