Alkyl Vinyl Ethers Research Articles

Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

Abstract. An important fraction of secondary organic aerosol (SOA) formed by atmospheric oxidation of diverse volatile organic compounds (VOC) has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006), we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI) formed during the ozonolysis reaction, which were CH2O2 (mass 46) for alkyl vinyl ethers (AVE) and C2H4O2 (mass 60) for ethyl propenyl ether (EPE). In the present work, we extend our previous study to another enol ether (ethyl butenyl ether EBE) and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene). Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS). SOA filter samples were collected and chemically characterized off-line by ESI(+)/TOF MS and ESI(+)/TOF MS/MS, and elemental compositions were determined by ESI(+)/FTICR MS and ESI(+)/FTICR MS/MS. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study. Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI) formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74) for ethyl butenyl ether (EBE), trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8O2 (mass 88) for \\textit{trans}-4-octene. Analogous fragmentation pathways among the oligomers formed by gas-phase ozonolysis of the different alkenes and enol ethers in our present and previous study, characterized by successive losses of the respective CI-like chain unit as a neutral fragment, indicate a similar principal structure. In this work, we confirm the basic structure of a linear oligoperoxide – [CH(R)-O-O]n – for all detected oligomers, with the repeated chain unit CH(R)OO corresponding to the respective major CI. The elemental compositions of parent ions, fragment ions and fragmented neutrals determined by accurate mass measurements with the FTICR technique allow us to assign a complete structure to the oligomer molecules. We suggest that the formation of the oligoperoxidic chain units occurs through a new gas-phase reaction mechanism observed for the first time in our present work, which involves the addition of stabilized CI to organic peroxy radicals. Furthermore, copolymerization of CI simultaneously formed in the gas phase from two different unsaturated compounds is shown to occur during the ozonolysis of a mixture of \\textit{trans}-3-hexene and ethyl vinyl ether (EVE), leading to formation of oligomers with mixed chain units C3H6O2 (mass 74) and CH2O2 (mass 46). We therefore suggest oligoperoxide formation by repeated peroxy radical-stabilized CI addition to be a general reaction pathway of small stabilized CI in the gas phase, which represents an alternative way to high-molecular products and thus contributes to SOA formation.

Coordination Copolymerization of Polar Vinyl Monomers H2CCHX

Rising to the challenge: Neutral phosphinosulfonate PdII complexes were recently demonstrated to be versatile catalysts even for the challenging insertion copolymerization of polar functionalized vinyl comonomers H2CCHX, such as acrylonitrile, vinyl acetate, and alkyl vinyl ethers (see scheme, MA=methyl acrylate).

Living cationic polymerization of dihydrofuran and its derivatives

Cationic polymerization of 2,3-dihydrofuran (DHF) and its derivatives was examined using base-stabilized initiating systems with various Lewis acids. Living cationic polymerization of DHF was achieved using Et1.5AlCl1.5 in toluene in the presence of THF at 0 °C, whereas it has been reported that only less controlled reactions occurred at 0 °C. Monomer-addition experiments of DHF and the block copolymerization with isobutyl vinyl ether demonstrated the livingness of the DHF polymerization: the number–average molecular weight of the polymers shifted higher with low polydispersity as the polymerization proceeded after the monomer addition. Furthermore, this base-stabilized cationic polymerization system allowed living polymerization of ethyl 1-propenyl ether and 4,5-dihydro-2-methylfuran at −30 and −78 °C, respectively. In the polymerization of 2,3-benzofuran, the long-lived growing species were produced at −78 °C. The obtained polymers have higher glass transition temperatures compared to poly(acyclic alkyl vinyl ether)s. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4495–4504, 2008

Synthesis of poly(vinyl ether) plastics for optical use by cationic copolymerization of tricyclodecyl vinyl ether with n‐butyl vinyl ether

Cationic copolymerizations of 8-vinyloxytricyclo[5.2.1.02,6]decane (TCDVE; tricyclodecane unit-containing vinyl ether) with n-butyl vinyl ether (NBVE) as a linear alkyl vinyl ether were undertaken in toluene solvent with living cationic initiators and BF3OEt2 as a non-living initiator. The Tg's of the copolymers of TCDVE and NBVE [poly(TCDVE-ran-NBVE)] was controlled by changing the copolymer composition. The copolymers showed similar transparency to those of polymethyl methacrylate (PMMA) and polycarbonate (PC), which are conventional optical plastics, and even lower specific gravity and water absorption than PMMA and PC. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Copolymerization of Ethylene and Alkyl Vinyl Ethers by a (Phosphine- sulfonate)PdMe Catalyst

The neutral complex (PO−OMe)PdMe(py) (1, PO−OMe = 2-[bis(2-OMe−Ph)phosphino]-4-methylbenzenesulfonate) polymerizes ethylene to a linear polymer with 1−10 branches/103 carbons (mostly methyl) and vinyl and 2-olefin unsaturated end groups. Complex 1 copolymerizes ethylene and alkyl vinyl ethers (CH2CHOR, 2a−c: R = tBu (a), Et (b), Bu (c)) in toluene at 60−100 °C to linear copolymers containing up to 7 mol % of vinyl ether. Addition of CH2CHOR lowers the polymerization rate and the polymer molecular weight. The copolymer structures are similar to that of homopolyethylene generated under the same conditions. The major comonomer units are −CH2CH(OR)CH2− (I) and CH3CH(OR)CH2− (II). The ethylene/CH2CHOR copolymers can be converted to hydroxy- and bromo-polyethylene. The results of control experiments argue against cationic and radical mechanisms for the copolymerization, and an insertion mechanism is proposed. The reaction of base-free (PO−OMe)PdMe with CH2CHOEt yields the adduct (PO−OMe)PdMe(CH2CHOEt), which undergoes 1,2-insertion to generate (PO−OMe)PdCH2CH(OEt)Me.

CAN‐Catalyzed Three‐Component Reaction Between Anilines and Alkyl Vinyl Ethers: Stereoselective Synthesis of 2‐Methyl‐1,2,3,4‐tetrahydroquinolines and Studies on Their Aromatization.

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A concise effective deprotection of spiro 3-cyclic thiaza ketal of steroidal 1,4-dien-3-one

An effective deprotective method of spiro 3-cyclic thiaza ketal of steroidal 1,4-dien-3-ones using alkyl vinyl ether in the presence of protic acid followed by the treatment of aqueous alkali was described. This novel protocol could be fulfilled under mild condition with high yield. The mechanism mediated by a carbonium ion formed in situ was clarified by the capture of the cleaved fragment.

CAN-catalyzed three-component reaction between anilines and alkyl vinyl ethers: stereoselective synthesis of 2-methyl-1,2,3,4-tetrahydroquinolines and studies on their aromatization

The CAN-catalyzed reaction between anilines and vinyl ethers at room temperature provides a convenient and efficient access to 4-alkoxy-2-methyl-1,2,3,4-tetrahydroquinolines. This reaction is stereoselective, favouring a cis arrangement for the alkoxy and methyl groups, and involves a three-component process that leaves a molecule of alcohol as the only side product. 2-Methylquinoline derivatives were efficiently prepared from 4-alkoxy-2-methyl-1,2,3,4-tetrahydroquinolines by Pd–C-promoted dehydrogenation.

Formation of secondary organic aerosol and oligomers from the ozonolysis of enol ethers

Abstract. Formation of secondary organic aerosol has been observed in the gas phase ozonolysis of a series of enol ethers, among them several alkyl vinyl ethers (AVE, ROCH=CH2), such as ethyl, propyl, n-butyl, iso-butyl, t-butyl vinyl ether, and ethyl propenyl ether (EPE, C2H5OCH=CHCH3). The ozonolysis has been studied in a 570 l spherical glass reactor at ambient pressure (730 Torr) and room temperature (296 K). Gas phase reaction products were investigated by in-situ FTIR spectroscopy, and secondary organic aerosol (SOA) formation was monitored by a scanning mobility particle sizer (SMPS). The chemical composition of the formed SOA was analysed by a hybrid mass spectrometer using electrospray ionization (ESI). The main stable gas phase reaction product is the respective alkyl formate ROC(O)H, formed with yields of 60 to 80%, implying that similar yields of the corresponding excited Criegee Intermediates (CI) CH2O2 for the AVE and CH3CHO2 for EPE are generated. Measured SOA yields are between 2 to 4% for all enol ethers. Furthermore, SOA formation is strongly reduced or suppressed by the presence of an excess of formic acid, which acts as an efficient CI scavenger. Chemical analysis of the formed SOA by ESI(+)/MS-TOF allows to identify oligomeric compounds in the mass range 200 to 800 u as its major constituents. Repetitive chain units are identified as CH2O2 (mass 46) for the AVE and C2H4O2 (mass 60) for EPE and thus have the same chemical compositions as the respective major Criegee Intermediates formed during ozonolysis of these ethers. The oligomeric structure and chain unit identity are confirmed by HPLC/ESI(+)/MS-TOF and ESI(+)/MS/MS-TOF experiments, whereby successive and systematic loss of a fragment with mass 46 for the AVE (and mass 60 for EPE) is observed. It is proposed that the oligomer has the following basic structure of an oligoperoxide, -[CH(R)-O-O]n-, where R=H for the AVE and R=CH3 for the EPE. Oligoperoxide formation is thus suggested to be another, so far unknown reaction of stabilized Criegee Intermediates in the gas phase ozonolysis of oxygen-containing alkenes leading to SOA formation.

New method of production of vinyl ether by vapor phase intramolecular dehydration of glycol ether over solid catalysts

We found that the intramolecular dehydration of glycol ether (2-alkoxyethanol or 2-aryloxyethanol) to vinyl ether (alkyl vinyl ether or aryl vinyl ether) occurs when glycol ether is made contacted with metal oxide catalysts in the vapor phase. The catalytic performance of SiO 2 catalyst alone was very low. Both the conversion of 2-alkoxyethanol and the selectivity for alkyl vinyl ether was markedly increased by the addition of cesium oxide to SiO 2. The high activity and selectivity are considered to be due to the presence of both weak acid sites and weak base sites on the modified SiO 2.

Calculation of the Arrhenius Parameters for the Pyrolysis of Some Alkyl Vinyl Ethers Using Mopac

Calculation of the Arrhenius Parameters for the Pyrolysis of Some Alkyl Vinyl Ethers Using Mopac

Hydrophosphination of alkoxyalkenes catalyzed by transition metal complexes

Diphenylphosphine adds to alkyl vinyl ethers in the presence of Ni(II) and Pd(II) complexes with a high regioselectivity, leading to exclusive formation of the corresponding Markownikoff adducts which were isolated as 1-alkoxyalkyl(diphenyl)phosphine oxides via oxidation with hydrogen peroxide.

Generation of quinone methide from aminomethyl(hydroxy)arenes precursors in aqueous solution

o-Quinone methides (QMs) are an important reactive intermediate for organic synthetic and biological standpoints of view. Photochemical and thermal transformation of N, N-dialkyl-9-aminomethyl-10-phenanthrols and their naphthalene analogs, which act as QM precursors, has been studied. These precursors readily reacted with alkyl vinyl ethers to give 2-alkoxydibenzo[ f, h]chroman and 2-alkoxybenzo[ f]chroman, respectively. Thermal and photochemical generation of QM was accelerated by the presence of water molecule in reaction solvents and by the formation of anionic micelle and vesicle.

Nucleophilic Addition to Acetylenes in Superbasic Catalytic Systems: XIII. Fluoride Cesium Containing Systems, Efficient Catalysts for Alkanols Vinylation

New catalytic systems CsF-MOH (M = Li, Na) were developed for the synthesis of alkyl vinyl ethers comparable in efficiency to cesium alcoholates. The addition of primary and secondary alcohols to acetylene occurs in the presence of these systems at the atmospheric (DMSO, 100°C) or at enhanced (without solvent, 135–140°C) acetylene pressure and affords alkyl vinyl ethers in up to 93% yield.

Preparation of sulfonated crosslinked PTFE- graft-poly(alkyl vinyl ether) membranes for polymer electrolyte membrane fuel cells by radiation processing

New polymer electrolyte membranes having sulfonic acid groups for polymer electrolyte membrane fuel cell applications were prepared by simultaneous radiation-induced grafting method. The poly(tetrafluoroethylene) (PTFE) films, crosslinked by electron-beam radiation at molten temperature, were used as substrates for grafting of two alkyl vinyl ether monomers, propyl vinyl ether ( nPVE) and isopropyl vinyl ether ( iPVE), under controlled grafting conditions followed by sulfonation reactions. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), water contact angle and Fourier transform infrared (FT-IR) were used to characterize the crosslinked PTFE (cPTFE) and grafted cPTFE films. The degree of grafting was found to be dependent on the grafting parameters such as irradiation temperature and Lewis acid catalyst, in which in the presence of Lewis acid catalyst or at a temperature close to the boiling point of each monomer, the grafting reaction significantly accelerated even when the relatively low dose was irradiated. Finally, the grafted cPTFE films were sulfonated in a chlorosulfonic acid solution. In spite of the lower ion-exchange capacity (0.75 mmol/g), the membrane synthesized in this study showed a proton conductivity as high as the Nafion 112.

A Tandem Nucleophilic Addition, Defluorination and Destannylation. Stereospecific Synthesis of Trifluoromethylated Alkyl and Aryl Vinyl Ethers.

AbstractFor Abstract see ChemInform Abstract in Full Text.

19F and 13C spectra of fluorinated and partially fluorinated vinyl alkyl ethers

Fluorine, hydrogen, and 13C NMR spectral data have been obtained for vinyl alkyl ethers containing fluorines. Some of the molecules are perfluorinated and others include hydrogen, bromine, and chlorine substituents. New generalizations regarding F F spin–spin coupling are developed and used, along with previously recognized correlations, in the confirmation of structures and the assignments of resonances. 13C spectroscopy, especially the analysis of 13C 19F coupling, is critical in several of the structure determinations. Chlorine isotope effects on fluorine chemical shifts are observed when the chlorine and fluorine are attached to the same carbon, and are also used in the structure analyses. Long-range couplings between fluorines in the vinyl group and fluorines in the alkyl group are interpreted in terms of molecular geometry which allows certain of the alkyl fluorines to “touch” the fluorines cis and gem to the ether oxygen but not the fluorine trans to the oxygen. Two bond 13C 19F coupling across the vinyl double bond is found to vary dramatically with the electronegativity of the vinyl substituents in the ethers, in accordance with previous observations for olefins.

Atom‐Economic Synthesis of Tertiary 2‐Alkoxyethylphosphine Sulfides.

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Vinyl ether-modified poly(hydrogen silsesquioxanes) as dielectric materials

Vinyl ether-modified poly(hydrogen silsesquioxanes) or PHSQ were prepared via a platinum-catalyzed hydrosilylation reaction of PHSQ with an alkyl vinyl ether (VE) in toluene. The product formed in a near quantitative yield and its composition was characterized by multinuclear magnetic resonance spectroscopy. Multi-detector size exclusion chromatography revealed that relative to the PHSQ starting material, the PHSQ–VEs increased in molecular weight and radius of gyration, and the relationship between intrinsic viscosity and molecular weight suggested a branched structure. Thermal analyses indicated a cure onset around 100 °C; an onset of thermal decomposition at ca. 230 °C; and mass loss completed by 550 °C. Evolved gas analysis from thermogravimetric experiments revealed the initial elimination of the ethylene linkage, followed by cleavage of the carbon–carbon bonds. The materials prepared by pyrolysis at 425 °C were porous. Nitrogen porosimetry measured an increase in microporosity—from 0.187 to 0.295 cm3 g−1 (<5 nm)—when the VE content was increased from 10 to 50 wt%. The PHSQ–VEs were spin-coated onto silicon wafers and cured either at 400, 425, or 450 °C. The dielectric constant of the spin-coated films ranged from 2.3 to 3.0, and the modulus was between 2.2 and 12.9 GPa depending on material composition.

Photosensitive copolymers with various types of azobenzene side groups synthesized by living cationic polymerization

Well-defined photoresponsive polymers of vinyl ethers with various azo side groups were synthesized via living cationic copolymerization using Et1.5AlCl1.5 in the presence of an ester as an added base. Despite the apparently undesirable structures, too basic or bulky, of azo-containing monomers for cationic polymerization, all copolymerizations with an alkyl vinyl ether proceeded with livingness to yield the product polymers with extremely narrow MWDs (Mw/Mn = 1.06−1.13). It should be noted that living polymers were produced even from a monomer with the dimethylamino group. The different azo groups in the product copolymers permitted reversible photo-responsive isomerization at a specific wavelength related to the structure of the azo group.