- Degradation in Order: Simple and Versatile One-Pot Combination of Two Macromolecular Concepts to Encode Diverse and Spatially Regulated Degradability Functions
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The clever one-pot combination of two macromolecular concepts, ring-opening polymerization (ROP) and step-growth polymerization (SGP), is demonstrated to be a simple, yet powerful tool to design a library of sequence-controlled polymers with diverse and spatially regulated degradability functions. ROP and SGP occur sequentially at room temperature when the organocatalytic conditions are switched from basic to acidic, and each allows the encoding of specific degradable bonds. ROP controls the sequence length and position of the degradability functions, while SGP between the complementary vinyl ether and hydroxyl chain-ends enables the formation of acetal bonds and high-molar-mass copolymers. The result is the rational combination of cleavable bonds prone to either bulk or surface erosion within the same macromolecule. The strategy is versatile and offers higher chemical diversity and level of control over the primary structure than current aliphatic polyesters or polycarbonates, while being simple, effective, and atom-economical and having potential for scalability.
- Fuoco, Tiziana
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- Liquid-phase Oxidation of 1,2-Ethane Diol
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The oxidation rate and the kind of oxidation products in the reaction of 1,2-ethane diol (1) with molecular oxygen in liquid phase at 150 deg C were investigated. 1 has a very low oxidation rate.Cu-, Zn-, Fe-, Co- and Al-acetylacetonates as catalysts increase the reaction rate.The main-products of the investigated reaction are the 1,3-dioxolan (2), the 2-methyl-1,3-dioxolan (3) and the 2-methylol-1,3-dioxolan (4).The formation of formic and acetic acids and of the 1,3-dioxolanes is proved by GC, DC and HPLC.
- Schnurpfeil, D.,Maurer, G.
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- Synthesis of ZSM-22 and Testing Its Catalytic Properties in the Ethylene Oxide Isomerization Reaction
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Abstract: The influence of the key parameters of the synthesis of a TON-type zeolite (ZSM-22) with or without an organic structure-directing agent on its phase composition has been established. The optimal composition of the reaction mixture and the crystallization time of ZSM-22 in the presence of 1,6-diaminohexane under static conditions have been determined. The dynamics of the formation of an impurity ZSM-5 by cocrystallization during the synthesis with stirring has been revealed. For zeolite ZSM-22 synthesized using the template-free procedure, the most important factors affecting the crystallinity and the crystallization time are the synthesis temperature, the amount of seed, and agitation of the reaction mixture. The zeolites synthesized according to the both procedures have been examined in the reaction of isomerization of ethylene oxide to acetaldehyde. Zeolite ZSM-22 obtained without adding the template is not inferior in activity to the zeolite of the same structure prepared in the presence of 1,6-diaminohexane. Moreover, it exhibits higher selectivity of ethylene oxide conversion to acetaldehyde. The complete conversion of ethylene oxide has been observed on ZSM-22 zeolites of both types at a reaction temperature of 400°C, the selectivity of its conversion to acetaldehyde being at least 93%.
- Lazareva,Piryutko,Chernyavskii,Kharitonov
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- Catalysis, kinetic and mechanistical studies for the transformation of ethylene glycol by alumina and silica gel under autogenous pressure and solvent-free conditions
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A kinetic and mechanistical studies of the new pathway for competitive transformation of ethylene glycol by alumina and silica gel have been described. Commercial alumina (Al com), synthetic alumina (Al syn), commercial silica gel (Si com) and synthetic silica gel (Si syn) were used for the transformation of ethylene glycol to a mixture of diethylene glycol, 1,4-dioxane and 2-methyl-1,3-dioxolane via acetaldehyde by heating at 150 °C under autogenous pressure without solvent. The results show that the yield of these three products strongly depends on the nature of the used catalyst and the reaction time.
- Rohand, Taoufik,Tanemura, Kiyoshi
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p. 387 - 394
(2021/06/25)
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- Photocatalytic Synthesis of 1,3-Dioxacyclanes from Diols and Primary Alcohols Effected by a System FeCl3–NaNO2/O2(Air)
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Diols and primary alcohols were subjected to the action of a system FeCl3–NaNO2/O2 (air) under mercury lamp irradiation to synthesize unsubstituted and 2-methyl-1,3-dioxacyclanes: 1,3-dioxolane, 1,3-dioxepane, 1,3-dioxocane, 2-methyl-1,3-dioxolane, 2-methyl-1,3-dioxepane, 2-methyl-1,3-dioxocane. The probable mechanism of the photocatalytic synthesis of 1,3-dioxacyclanes was described by an example of 2-methyl-1,3-dioxolane.
- Makhmutov
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p. 1710 - 1714
(2019/02/14)
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- Synthesis of dioxolanes and oxazolidines by silica gel catalysis
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Abstract: Ethylene glycol condensed with carbonyl compounds in the presence of silica gel or alumina, without solvent and under pressure, affords 1,3-dioxolanes. 2-Amino-2-methylpropanol also condensed with carbonyl compounds in the presence of silica gel or an acid-activated clay, without solvent and under pressure, produces oxazolidines. To explain these results, we propose that the glycol and the aminopropanol react with Br?nsted (H+) and Lewis acid sites (Si and Al) located on the surface of the catalysts, leading to the products via various ionic intermediates.
- Rohand, Taoufik,Savary, Jér?me,Markó, István E.
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p. 1429 - 1436
(2018/06/25)
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- Preparation method of cyclic acetal
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The invention discloses a preparation method of cyclic acetal. The method is characterized in that long-chain polyhydroxy compounds and small-molecular aldehydes are used as the substrates, long-chain weak-polarity molecules are used as the solvent, and the aldehydes are condensed with the hydroxyl groups at two ends of the polyhydroxy compounds under the effect of a catalyst to form the intramolecular cyclic acetal. Compared with a traditional acetal preparation method, the method has the advantages that the property differences of the solvent, reactants and the substrates are utilized to allow the aldehydes to be easy to react with the hydroxyl groups, and the cyclic acetal proportion in the product is high; the conversion rate of the aldehyde compounds reaches above 80%, and the selectivity of the cyclic acetal can reach above 80%.
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Paragraph 0035; 0036; 0037; 0038
(2017/08/29)
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- METHOD OF MANUFACTURING 2-METHYL-1,3-DIOXOLANE IN A SOLID STATE POLYCONDENSATION PROCESS
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The invention relates to a method for producing 2-methyl-1,3-dioxolane from a polyester solid state polymerization system. The method comprises using an acid catalyst to effectuate the conversion of acetaldehyde present within the system to 2-methyl-1,3-dioxolane, which can be readily removed in the ethylene glycol stream.
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Paragraph 13; 14
(2017/06/02)
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- Production of aldehydes from 1,2-alkanediols over silica-supported WO3 catalyst
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Vapor-phase dehydration of several 1,2-alkanediols, such as 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol and 1,2-pentanediol, to produce corresponding aldehydes was investigated over silica-supported WO3 catalyst, which was prepared by impregnation method and then calcined at 320?°C. Higher than 90% yield of aldehydes could be achieved over WO3/SiO2 catalyst at 250?°C with a feed of 20% aqueous 1,2-alkanediol solution. Both Br?nsted and Lewis acid sites exist on WO3/SiO2 catalyst, while Br?nsted acid sites are proposed to be the active species for the formation of aldehyde. High concentrations of H2O were effective for inhibiting the intermolecular reaction and improving the selectivity to aldehydes. The dehydration of different 1,2-alkanediols was compared under different reaction conditions. The reactivity of 1,2-ethanediol was low and the product distribution was several comparing with those of the other 1,2-alkanediols. Cyclic acetal, which was generated by the cyclodehydration of the produced aldehyde with another 1,2-alkanediol, was a main by-product, and the formation of acetal was affected by both the temperature and the carbon-chain length of the 1,2-alkanediols.
- Sun, Daolai,Yamada, Yasuhiro,Sato, Satoshi,Suganuma, Satoshi,Katada, Naonobu
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p. 164 - 171
(2016/09/09)
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- METHOD OF MANUFACTURING 2-METHYL-1, 3-DIOXOLANE IN A SOLID STATE POLYCONDENSATION PROCESS
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The invention relates to a method for producing 2-methyl-1,3-dioxolane from a polyester solid state polymerization system. The method comprises using an acid catalyst to effectuate the conversion of acetaldehyde present within the system to 2-methyl-1,3-dioxolane, which can be readily removed in the ethylene glycol stream.
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Page/Page column 11; 12
(2015/07/07)
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- Cyclodehydration of diethylene glycol over Ag-modified Al2O3 catalyst
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Vapor-phase cyclodehydration of diethylene glycol (DEG) into 1,4-dioxane (DOX) were performed over several solid acid catalysts, such as Al2O3, SiO2-Al2O3, Beta and MFI zeolites. All the catalytic activity gradually decreased with time on stream, especially Beta and MFI zeolites with strong acidic property. The catalysts were modified with silver metal for stabilizing the catalytic activity: Al2O3 modified with 1 wt.% Ag2O showed the best catalytic performance. Characterizations such as XRD, TPD and FTIR were performed for analyzing the carbonaceous compound deposited on the catalysts after reaction and investigating the effect of the addition of Ag2O onto Al2O3. Polyethylene glycol was proposed as the carbonaceous compound by FTIR analysis. The modification of Ag was found to decrease the averaged acid strength of Al2O3, which is supposed to be effective for inhibiting carbon deposition and stabilizing the catalytic activity. It was also found that H2, as a carrier gas, was indispensable for stabilizing the conversion of DEG into DOX. Silver metal would work as a remover of the product on the catalyst surface together with H2 to prevent carbon deposition. Over Al2O3 modified with 1 wt.% Ag2O, a stable DOX selectivity of 90% with a complete conversion was achieved at 250 °C and a contact time of 156.8 g h mol-1.
- Sun, Daolai,Wang, Junjie,Yamada, Yasuhiro,Sato, Satoshi
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p. 422 - 430
(2015/10/28)
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- Replacing conventional carbon nucleophiles with electrophiles: Nickel-catalyzed reductive alkylation of aryl bromides and chlorides
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A general method is presented for the synthesis of alkylated arenes by the chemoselective combination of two electrophilic carbons. Under the optimized conditions, a variety of aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant (-OH, -NHTs, -OAc, -OTs, -OTf, -COMe, -NHBoc, -NHCbz, -CN, -SO2Me), and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture. The reaction displays different chemoselectivity than conventional cross-coupling reactions, such as the Suzuki-Miyaura, Stille, and Hiyama-Denmark reactions. Substrates bearing both an electrophilic and nucleophilic carbon result in selective coupling at the electrophilic carbon (R-X) and no reaction at the nucleophilic carbon (R-[M]) for organoboron (-Bpin), organotin (-SnMe3), and organosilicon (-SiMe2OH) containing organic halides (X-R-[M]). A Hammett study showed a linear correlation of σ and σ(-) parameters with the relative rate of reaction of substituted aryl bromides with bromoalkanes. The small ρ values for these correlations (1.2-1.7) indicate that oxidative addition of the bromoarene is not the turnover-frequency determining step. The rate of reaction has a positive dependence on the concentration of alkyl bromide and catalyst, no dependence upon the amount of zinc (reducing agent), and an inverse dependence upon aryl halide concentration. These results and studies with an organic reductant (TDAE) argue against the intermediacy of organozinc reagents.
- Everson, Daniel A.,Jones, Brittany A.,Weix, Daniel J.
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supporting information; experimental part
p. 6146 - 6159
(2012/05/07)
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- PROCESS FOR THE PRODUCTION OF ETHYLENE GLYCOL
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The present invention provides a process for the production of monoethylene glycol, said process comprising the steps of: (a) reacting ethylene oxide with a ketone in the presence of a solid acidic catalyst to form a ketal; and (b) hydrolysing the ketal with water to form monoethylene glycol, wherein the ketone contains in the range of from 4 to 20 carbon atoms.
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Page/Page column 10-12; 5/7
(2011/02/24)
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- Hydrothermal synthesis of two cationic bismuthate clusters: An alkylenedisulfonate bridged hexamer, [Bi6O4(OH) 4(H2O)2][(CH2)2(SO 3)2]3 and a rare nonamer templated by triflate, [Bi9O8(OH)6][CF3SO 3]5
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This paper reports the synthesis, characterization, and application of two cationic bismuthate clusters by anion templating. The compounds were synthesized under mild hydrothermal treatment and characterized by powder and single-crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. The first material consists of a cationic hexanuclear bismuthate cluster octahedral in geometry and linked by 1,2-ethanedisulfonate molecules. This structure is thermally stable to about 235 °C. In the second compound, discrete cationic nonanuclear bismuthate clusters interact electrostatically with trifluoromethanesulfonate anions to pack into a nearly layered assembly. The material undergoes a transformation to Bi2O3 upon loss of the triflate groups at about 385 °C. Both materials demonstrate the use of sulfonate groups for the anion-directed assembly of these rare cationic inorganic structures. The application of the 3D octahedral bismuth cluster material toward acidic heterogeneous catalysis is also reported.
- Rogow, David L.,Fei, Honghan,Brennan, Daniel P.,Ikehata, Mariko,Zavalij, Peter Y.,Oliver, Allen G.,Oliver, Scott R. J.
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experimental part
p. 5619 - 5624
(2010/08/05)
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- Methyl acetate purification and carbonylation
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Disclosed is a method for removing aldehyde impurities from a methyl acetate supply. The method comprises reacting the methyl acetate supply with a polyol and converting the aldehyde impurities to cyclic acetals. The acetals are subsequently removed from the methyl acetate supply by, e.g., distillation. The purified methyl acetate supply is used for carbonylation to produce acetic acid.
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Page/Page column 5
(2008/12/06)
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- Nucleophilic addition to acetylenes in superbasic catalytic systems: XIV. Vinilation of diols in a system CsF-NaOH
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A new catalytic system CsF-NaOH was developed for the synthesis of mono- and divinyl ethers of alkanediols exceeding in efficiency KOH. The nucleophilic addition of diols to acetylene in the presence of this system occurs both at enhance pressure (without solvent, 140-160°C) and atmospheric pressure (in DMSO medium, 100°C) of acetylene. Conditions were established of a selective preparation in a high yield of divinyl ethers from diols. 2005 Pleiades Publishing, Inc.
- Oparina,Khil'ko,Chernyshova,Shaikhudinova,Parshina,Preiss,Henkelmann,Trofimov
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p. 661 - 666
(2007/10/03)
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- The continuous acid-catalyzed dehydration of alcohols in supercritical fluids: A new approach to the cleaner synthesis of acetals, ketals, and ethers with high selectivity
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We report a new continuous method for forming ethers, acetals and ketals using solid acid catalysts, DELOXAN ASP or AMBERLYST 15, and supercritical fluid solvents. In the case of ether formation, we observe a high selectivity for linear alkyl ethers with little rearrangement to give branched ethers. Such rearrangement is common in conventional syntheses. Our approach is effective for a range of n-alcohols up to n-octanol and also for the secondary alcohol 2-propanol. In the reaction of phenol with an alkylating agent, the continuous reaction can be tuned to give preferential O- or C- alkylation with up to 49% O-alkylation with supercritical propene. We also investigate the synthesis of a range of cyclic ethers and show an improved method for the synthesis of THF from 1,4-butandiol under very mild conditions.
- Gray, William K.,Smail, Fiona R.,Hitzler, Martin G.,Ross, Stephen K.,Poliakoff, Martyn
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p. 10711 - 10718
(2007/10/03)
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- Exchange reaction of linear acetals with ethylene glycol by 13C NMR spectroscopy
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Reaction of linear acetals RCH(OR′)2 (R = H, CH3, C2H5; R′ = CH3, C2H5, C3H7) with ethylene glycol in a neutral medium at 25°C was studied by 13C NMR spectroscopy. The equilibrium compositions of the reaction mixtures and their dependence on the reactant molar ratio were determined. It is shown that under the experimental conditions used dimethoxymethane fails to react with ethylene glycol, and the reactions of the other acetals yield much cyclic acetals, 1,3-dioxolanes. The reaction of 2-methyl-1,3-dioxolane with methanol gives the same products as the reaction of 1,1-dimethoxyethane with ethylene glycol.
- Balashov,Krasnov,Danov,Chernov
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p. 1421 - 1426
(2007/10/03)
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- Synthesis of alkyl-substituted 1,3-dioxolanes by catalytic dehydration of 1,2-glycols
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The kinetics of the acid-catalyzed reactions of dehydration of ethylene glycol and 1,2-propylene glycol to respectively acetaldehyde and propionic aldehyde and of condensation of the aldehydes with the glycols were studied. The dependences of the apparent rate constants on temperature and catalyst concentration were determined. A mathematical model of the reactions studied was proposed.
- Balashov,Danov,Chernov,Kvashennikov
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p. 1418 - 1420
(2007/10/03)
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- Thermolysis of the benzene anion radical 18-crown-6 complex
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The C-O and G-H bonds of 18-crown-6 are activated when 18-crown-6 is complexed with the potassium salt of the benzene anion radical. Evacuated glass bulbs containing the solid anion radical salt of potassium 18-crown-6 benzene anion radical were plunged into a bath at 320 C, resulting in mini-explosions and generating a series of compounds including dioxane, 2-methyl1,3-dioxolane, divinyl ether, hydrogen, methane, and 15-crown-5. Deuterium labeling studies proved that all of these compounds originated from the 18-crown-6. Further, these labeling studies were an aid in discerning the mechanism of the decomposition. Benzene, 1,4-cyclohexadiene, and cyclohexene were also generated. The last two originated from the reaction of the anion radical of benzene with hydrogen.
- Stevenson, Cheryl D.,Morgan, Grant
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p. 7694 - 7697
(2007/10/03)
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- Identification of 1,3-dioxanes and 1,3-dioxolanes as malodorous compounds at trace levels in river water, groundwater, and tap water
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A study of organic compounds imparting odor problems in river waters and groundwaters has been conducted. The Tordera aquifer located in Barcelona and Girona (NE Spain) is the water supply reserve for many seasonally crowded villages on the coast. Closed loop stripping analysis (CLSA) and flavor profile analysis (FPA) have been employed as analytical tools to identify the compounds responsible for the odor complaints. The feasibility of purge-and- trap (P and T) has also been evaluated. The 2-alkyl-5,5-dimethyl-1,3-dioxanes and 2-alkyl-4-methyl-1,3-dioxolanes were the most significant compounds identified in river water and groundwater with a threshold odor of 10 ng/L for 2-ethyl-5,5-dimethyl-1,3-dioxane (2EDD), the most malodorous compound. The analyses were carried out by HRGC/MS, and the synthesized 1,3-dioxanes and dioxolanes were characterized by CI-MS and EI-MS/MS techniques. A company, currently manufacturing saturated and unsaturated polyester resins, located in the upper course of the river, produced these compounds as byproducts during the synthesis of resins. The pollution by dioxanes and dioxolanes affected all the aquifer and slowly diminished to the ppt levels when the company was forced to correctly treat their wastewaters. Additional examples of the presence of dioxanes and dioxolanes in wastewaters of other resin plants and also tap water of Barcelona are shown. A study of organic compounds imparting odor problems in river waters and groundwaters has been conducted. The Tordera aquifer located in Barcelona and Girona (NE Spain) is the water supply reserve for many seasonally crowded villages on the coast. Closed loop stripping analysis (CLSA) and flavor profile analysis (FPA) have been employed as analytical tools to identify the compounds responsible for the odor complaints. The feasibility of purge-and-trap (P&T) has also been evaluated. The 2-alkyl-5,5-dimethyl-1,3-dioxanes and 2-alkyl-4-methyl-1,3-dioxolanes were the most significant compounds identified in river water and groundwater with a threshold odor of 10 ng/L for 2-ethyl-5,5-dimethyl-1,3-dioxane (2EDD), the most malodorous compound. The analyses were carried out by HRGC/MS, and the synthesized 1,3-dioxanes and dioxolanes were characterized by CI-MS and EI-MS/MS techniques. A company, currently manufacturing saturated and unsaturated polyester resins, located in the upper course of the river, produced these compounds as byproducts during the synthesis of resins. The pollution by dioxanes and dioxolanes affected all the aquifer and slowly diminished to the ppt levels when the company was forced to correctly treat their wastewaters. Additional examples of the presence of dioxanes and dioxolanes in wastewaters of other resin plants and also tap water of Barcelona are shown.
- Romero, Jordi,Ventura, Francesc,Caixach, Josep,Rivera, Josep,Gode, Llui Xavier,Ninerola, Josep Ma.
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p. 206 - 216
(2007/10/03)
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- OH radical initiated photooxidation of 2-ethoxyethanol under laboratory conditions related to the troposphere: Product studies and proposed mechanism
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The products formed by the hydroxyl radical-initiated oxidation of 2- ethoxyethanol (CH3CH2OCH2CH2OH) have been investigated by irradiating synthetic air mixtures containing the substrate, methyl nitrite, and nitric oxide at ppm levels in a Teflon bag reactor at room temperature. The decay of reactants and the formation of products were monitored by gas chromatography and mass spectrometry. The major products ethyl formate [HC(O)OCH2CH3], ethylene glycol monaformate [HC(O)OCH2CH2OH], ethylene glycol monaacetate [CH3C(O)OCH2CH2OH], and ethoxyacetaldehyde [CH3CH2OCH2C(O)H] give a quantitative mass balance with the decay of the substrate molecule. The yields of these products were 34 ± 10%, 36 ± 7%, 7.8 ± 2.4%, and 24 ± 13%, respectively, in terms of percent of 2-ethoxyethanol removed by the OH radical. The product distribution is explained by a mechanism involving initial OH attack at the three CH2 groups in 2-ethoxyethanol followed by the subsequent reactions of the resulting alkyl and alkoxy radicals. The decomposition reactions of the alkoxy radicals from 2-ethoxyethanol, which can take place either by C-C or C-O bond breaking, involve preferential C-C cleavage rather than C-O cleavage. Rate coefficients at room temperature for the reactions of OH radicals with ethoxyacetaldehyde and 2-methyl-1,3- dioxolane (CH3CHOCH2CH2O, a minor product) have been determined to be 16.6 x 10-12 and 9.4 x 10-12 cm3 molecule-1 s-1, respectively.
- Stemmler, Konrad,Mengon, Wolfgang,Kerr, J. Alistair
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p. 3385 - 3391
(2007/10/03)
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- Synthesis of 1,4-dioxene from diethylene glycol in the presence of bifunctional copper-containing catalysts. Effect of support on the selectivity of dioxene formation
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In the synthesis of 1,4-dioxene from diethylene glycol in the presence of a bifunctional copper-containing catalyst, the composition of the by-products has been studied and the effect of the support on the overall direction of the reactions has been investigated. It has been established that on Cu/SiO2, 1,4-dioxanone is formed together with dioxene, the yield of the former increasing with an increase in the content of copper in the catalyst. This is due to an increase in the dehydrogenating function of the latter. On the more acidic Cu/Al2O3, 1,4-dioxane is mainly obtained together with, to a lesser degree, methyl-1,3-dioxolane. This is due to the predominance of dehydration reactions followed by isomerization. Dioxene, dioxane, and methyldioxolane are formed on Cu/HNaY, and the yield of the latter increases with an increase in the degree of acidity (degree of decationization) of the zeolite. It is possible to increase the selectivity of dioxene formation substantially with the use of a catalyst with a moderately acidic zeolite, by varying its copper content and by dilution with water vapor. 1996 Plenum Publishing Corporation.
- Gitis,Neumoeva,Isagulyants
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- Transformation of 1,2-diols over perfluorinated resinsulfonic acids (Nafion-H)
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The transformations of 1,2-diols over perfluorinated resinsulfonic acids (Nafion-H) were studied, and correlations were examined between the structures of the investigated diols, the possible dehydration routes and the catalytic properties of Nafion-H. Comparisons were also made between the catalytic properties of Nafion-H and NaHX zeolite. Because of its stronger acidity, Nafion-H functions at temperatures considerably lower than those for the usual dehydrating catalysts, e.g. the zeolites. As is well established for other solid electrophilic catalysts, the dehydration of 1,2-diols mainly proceeds via the pinacol rearrangement. The lower temperatures and the stronger acidity of Nafion-H strongly favour the pinacol rearrangement versus 1,2-elimination. The reaction conditions are also advantageous for the formation of substituted 1,3-dioxolanes in a secondary condensation step between the unreacted diol and the primarily formed carbonyl compounds. Nafion-H gradually deactivates during long use, but it can be partially reactivated by washing with acetone.
- Bucsi,Bucsi, Imre,Molnar,Molnar, Arpad,Bartok,Bartok, Mihaly,Olah,Olah, George A.
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p. 8195 - 8202
(2007/10/02)
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- The electron spin resonance spectra of dioxene radical cations
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The electron spin resonance spectra of the radical cations of dioxene (1a), 2,3-dimethyldioxene (1b), 2,3-diphenyldioxene (1c), and benzodioxane (2) in fluid solution have been observed and analysed, with the help of ENDOR spectroscopy in the case of 1c.It is concluded that in 1c the molecule has overall C2 molecular symmetry.In all four compounds, the pseudo-axial and pseudo-equatorial protons of the methylene groups in the half-chair dioxene rings are distinguished by different hyperfine coupling constants, and simulation of the spectra over a range of temperatures has given the Arrhenius parameters for the ring inversion of 1a, 1b, and 2.Key words: ESR spectra, radical cation, 1,4-dioxene, inversion barrier.
- Davies, Alwyn G.,Shields, Charles J.,Evans, Jeffrey C.,Rowlands, Christopher C.
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p. 1748 - 1752
(2007/10/02)
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- Acyclic Analogs of Nucleosides. Synthesis of Hydroxyalkyl Derivatives of 2-Trifluoromethyl- and 2-Trifluoromethylthiobenzimidazole
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1-(2,3-Dihydroxypropyl)-, 1-(4-hydroxy-2-oxabutyl)-, 1-(3-hydroxymethyl-4-hydroxy-2-oxabutyl)-, 1-(1,5-dihydroxy-3-oxa-2-pentyl)-, 1-(5-hydroxy-3-oxa-2-pentyl)-, and 1-(4,5-dihydroxy-2-oxapentyl)-2-trifluoromethyl- and -2-trifluoromethylthiobenzimidazoles were obtained by condensation of trimethylsilyl derivatives of 2-substituted benzimidazoles with alkylating agents in the presence of SnCl4 or by direct alkylation of the sodium salts of the heterocycles.
- Yavorskii, A. E.,Stetsenko, A. V.,Gogoman, I. V.,Boiko, V. N.,Zavgorodnii, S. G.,et al.
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p. 514 - 518
(2007/10/02)
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- PYROLYTIC TRANSFORMATION OF THE VINYL MONOETHERS OF DIOLS IN THE PRESENCE OF ALKALIS
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The alkaline pyrolysis of the vinyl monoethers of diols takes place at 170-250 deg C and is accompanied by cycloacetalization (ethylene glycol, 1,3-propanediol), by processes involving cleavage of the C-O bonds (diethylene glycol, 1,4-butanediol), and also by the release of hydrogen, carbon dioxide, methane, ethane, acetylene, and C3 to C5 hydrocarbons.Distillation of ethylene glycol vinyl monoether with potassium hydroxide, sodium hydroxide, and lithium hydroxide can result in explosion as a result of the vigorous and exothermic release of gas.
- Trofimov, B. A.,Oparina, L. A.,Parshina, L. N.,Lavrov, V. I.,Grigorenko, V. I.,Zhumabekov, M. K.
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p. 1424 - 1428
(2007/10/02)
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- PHOTOCHEMICAL CHLOROTRIFLUOROETHYLATION OF 1,2-, 1,3-, AND 1,4-DIOLS
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The UV light-initiated reaction of chlorotrifluoroethylene with 1,2-ethanediol (I) proceeds only in the presence of acetone and affords 2-(2-chloro-1,1,2-trifluoroethyl)-2-methyl-1,3-dioxolane (VI).It has been proved that I is first photolyzed to acetaldehyde.Its acetalization in the reaction mixture gives 2-methyl-1,3-dioxolane (V) which then undergoes chlorotrifluoroethylation.The chlorotrifluoro derivative of 1,2-ethanediol XII was prepared by hydrolysis of 4-(2-chloro-1,1,2-trifluoroethyl)-2,2-dimethyl-1,3-dioxolane (XIII). 1,3-Propanediol (II) reacted to give 5-chloro-4,4,5-trifluoro-1,3-pentanediol (XVI).Analogous reaction of 1,4-butanediol (III) and 1,3-butanediol (IV) afforded, in addition to derivatives with chlorotrifluoroethyl group at the hydroxyl-bearing carbon atom (XVII from III, XIX and XX from IV), also the respective bis-chlorotrifluoroethyl derivatives XVIII and XXI as products arising by the 1,5- or 1,6-transfer in the radical intermediates.
- Dedek, Vaclav,Hemer, Ivan
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p. 2743 - 2752
(2007/10/02)
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- Solvent Effects on Equilibria of Addition of Nucleophiles to Acetaldehyde and the Hydrophilic Character of Diols
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Equilibria of addition of water, methanol, methanethiol, ammonia, methylamine, nitromethane, and ethylene glycol to acetaldehyde have been compared in water and in chloroform, and the partition coefficients of reactants and products between the two solvents have been estimated by direct and indirect methods.Single additions of oxygen nucleophiles were found to proceed equally favorably in either solvent, whereas single additions of sulfur, nitrogen, and carbon nucleophiles proceeded much further toward completion in water than in chloroform.Equilibria of acetal formation, involving methanol or ethylene glycol, were somewhat more favorable in chloroform than in water.Reexamination of the vapor pressures of ethylene glycol and related compounds over water indicated that their hydrophilic character was greater than had been supposed.
- Bone, Roger,Cullis, Paul,Wolfenden, Richard
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p. 1339 - 1343
(2007/10/02)
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- Rational Mechanism for Homogeneous Hydrogenation of Carbon Monoxide to Alcohols, Polyols, and Esters
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The products derived from synthesis gas conversion by homogeneous catalysis are concluded to be formed via the key intermediate formaldehyde.The intermediacy of formaldehyde is supported by reaction rate studies, comparison reactions of formaldehyde with synthesis gas, and the trapping of formaldehyde and glycolaldehyde intermediates during a reaction as their ethylene glycol acetals.Although the formation of formaldehyde from synthesis gas is themodynamically unfavorable, it is argued that the concentration of formaldehyde permitted by thermodynamics is more than sufficient for a transient intermediate.The overall mechanism incorporates only step that are already well established in the science of homogeneous catalysis.
- Fahey, Darryl R.
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p. 136 - 141
(2007/10/02)
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- Cyclodimerization of ethylene oxide
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The cyclodimerization of ethylene oxide is carried out using elemental iodine as catalyst and a sulfolane as the diluent to form 1,4-dioxane and 2-methyl-1,3-dioxolane.
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