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Martina H Stenzel - One of the best experts on this subject based on the ideXlab platform.
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a detailed on line ft nir and 1h nmr spectroscopic investigation into factors causing inhibition in Xanthate mediated vinyl acetate polymerization
Macromolecular Chemistry and Physics, 2004Co-Authors: Arnaud Favier, Thomas P Davis, Christopher Barnerkowollik, Martina H StenzelAbstract:Potential sources of inhibition have been investigated via in situ Fourier transform - near infra-red (FT-NIR) and off-line H-1 NMR spectroscopy in the RAFT/MADIX bulk polymerization of vinyl acetate (VA) in the presence of an O-isopropyl Xanthate, i.e. methyl (isopropoxycarbonothioyl)sulfanyl acetate. The very high reactivity of the vinyl acetate propagating radical makes it very vulnerable to oxygen, by-products generated during the Xanthate synthesis, and stabilizers present as impurities. These impurities induce strong and variable inhibition periods in the polymerization. In addition, the MADIX process, using Xanthates as reversible chain transfer agents, has been confirmed to be an efficient method for living VA polymerization. Congruent data are obtained when the monomer consumption with time is followed via both H-1 NMR and in situ FT-NIR spetroscopy. The Xanthate-mediated polymerization of VA exhibits no retardation effects and excellent control of the molecular weight distribution can be achieved, leading to poly(VA) of molecular weights exceeding 50 000 g . mol(-1) with relatively low polydispersities.
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a detailed on line ft nir and 1h nmr spectroscopic investigation into factors causing inhibition in Xanthate mediated vinyl acetate polymerization
Institute for Future Environments; Science & Engineering Faculty, 2004Co-Authors: Arnaud Favier, Thomas P Davis, Christopher Barnerkowollik, Martina H StenzelAbstract:Potential sources of inhibition have been investigated via in situ Fourier transform - near infra-red (FT-NIR) and off-line 1H NMR spectroscopy in the RAFT/MADIX bulk polymerization of vinyl acetate (VA) in the presence of an O-isopropyl Xanthate, i.e. methyl (isopropoxycarbonothioyl)sulfanyl acetate. The very high reactivity of the vinyl acetate propagating radical makes it vulnerable to oxygen, by-products generated during the Xanthate synthesis, and stabilizers present as impurities. These impurities induce strong and variable inhibition periods in the polymerization. In addition, the MADIX process, using Xanthates as reversible chain transfer agents, has been confirmed to be an efficient method for living VA polymerization. Congruent data are obtained when the monomer consumption with time is followed via both 1H NMR and in situ FT-NIR spectroscopy. The Xanthate-mediated polymerization of VA exhibits no retardation effects and excellent control of the molecular weight distribution can be achieved, leading to poly(VA) of molecular weights exceeding 50 000 g · mol-1 with relatively low polydispersities.
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Xanthate mediated living polymerization of vinyl acetate a systematic variation in madix raft agent structure
Macromolecular Chemistry and Physics, 2003Co-Authors: Martina H Stenzel, Lyndal Cummins, Evan G Roberts, Philipp Vana, Thomas P Davis, Christopher BarnerkowollikAbstract:Eight Xanthates were synthesized to induce living free radical polymerization of vinyl acetate. Four compounds, methyl (4-methoxyphenoxy)carbonothioylsulfanyl acetate, methyl (methoxycarbonothioyl)sulfanyl acetate, methyl (ethoxycarbonothioyl)sulfanyl acetate and methyl (isopropoxycarbonothioyl)sulfanyl acetate were identified as suitable MADIX/RAFT agents, yielding low polydispersity (PDI < 1.2) poly(vinyl acetate) of molecular weights exceeding 5 × 104 g · mol−1. All suitable MADIX/RAFT agents exhibited extended periods of inhibition (0.3 h < tinh < 10 h) and moderate rate retardation. The ability of these compounds to control vinyl acetate polymerization can be correlated with the electron density on the central carbon atom of the Xanthate. Electrospray ionization mass spectrometric analysis was performed to complete the investigation on the new MADIX/RAFT agents.
Christopher Barnerkowollik - One of the best experts on this subject based on the ideXlab platform.
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a detailed on line ft nir and 1h nmr spectroscopic investigation into factors causing inhibition in Xanthate mediated vinyl acetate polymerization
Macromolecular Chemistry and Physics, 2004Co-Authors: Arnaud Favier, Thomas P Davis, Christopher Barnerkowollik, Martina H StenzelAbstract:Potential sources of inhibition have been investigated via in situ Fourier transform - near infra-red (FT-NIR) and off-line H-1 NMR spectroscopy in the RAFT/MADIX bulk polymerization of vinyl acetate (VA) in the presence of an O-isopropyl Xanthate, i.e. methyl (isopropoxycarbonothioyl)sulfanyl acetate. The very high reactivity of the vinyl acetate propagating radical makes it very vulnerable to oxygen, by-products generated during the Xanthate synthesis, and stabilizers present as impurities. These impurities induce strong and variable inhibition periods in the polymerization. In addition, the MADIX process, using Xanthates as reversible chain transfer agents, has been confirmed to be an efficient method for living VA polymerization. Congruent data are obtained when the monomer consumption with time is followed via both H-1 NMR and in situ FT-NIR spetroscopy. The Xanthate-mediated polymerization of VA exhibits no retardation effects and excellent control of the molecular weight distribution can be achieved, leading to poly(VA) of molecular weights exceeding 50 000 g . mol(-1) with relatively low polydispersities.
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a detailed on line ft nir and 1h nmr spectroscopic investigation into factors causing inhibition in Xanthate mediated vinyl acetate polymerization
Institute for Future Environments; Science & Engineering Faculty, 2004Co-Authors: Arnaud Favier, Thomas P Davis, Christopher Barnerkowollik, Martina H StenzelAbstract:Potential sources of inhibition have been investigated via in situ Fourier transform - near infra-red (FT-NIR) and off-line 1H NMR spectroscopy in the RAFT/MADIX bulk polymerization of vinyl acetate (VA) in the presence of an O-isopropyl Xanthate, i.e. methyl (isopropoxycarbonothioyl)sulfanyl acetate. The very high reactivity of the vinyl acetate propagating radical makes it vulnerable to oxygen, by-products generated during the Xanthate synthesis, and stabilizers present as impurities. These impurities induce strong and variable inhibition periods in the polymerization. In addition, the MADIX process, using Xanthates as reversible chain transfer agents, has been confirmed to be an efficient method for living VA polymerization. Congruent data are obtained when the monomer consumption with time is followed via both 1H NMR and in situ FT-NIR spectroscopy. The Xanthate-mediated polymerization of VA exhibits no retardation effects and excellent control of the molecular weight distribution can be achieved, leading to poly(VA) of molecular weights exceeding 50 000 g · mol-1 with relatively low polydispersities.
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Xanthate mediated living polymerization of vinyl acetate a systematic variation in madix raft agent structure
Macromolecular Chemistry and Physics, 2003Co-Authors: Martina H Stenzel, Lyndal Cummins, Evan G Roberts, Philipp Vana, Thomas P Davis, Christopher BarnerkowollikAbstract:Eight Xanthates were synthesized to induce living free radical polymerization of vinyl acetate. Four compounds, methyl (4-methoxyphenoxy)carbonothioylsulfanyl acetate, methyl (methoxycarbonothioyl)sulfanyl acetate, methyl (ethoxycarbonothioyl)sulfanyl acetate and methyl (isopropoxycarbonothioyl)sulfanyl acetate were identified as suitable MADIX/RAFT agents, yielding low polydispersity (PDI < 1.2) poly(vinyl acetate) of molecular weights exceeding 5 × 104 g · mol−1. All suitable MADIX/RAFT agents exhibited extended periods of inhibition (0.3 h < tinh < 10 h) and moderate rate retardation. The ability of these compounds to control vinyl acetate polymerization can be correlated with the electron density on the central carbon atom of the Xanthate. Electrospray ionization mass spectrometric analysis was performed to complete the investigation on the new MADIX/RAFT agents.
Thomas P Davis - One of the best experts on this subject based on the ideXlab platform.
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a detailed on line ft nir and 1h nmr spectroscopic investigation into factors causing inhibition in Xanthate mediated vinyl acetate polymerization
Macromolecular Chemistry and Physics, 2004Co-Authors: Arnaud Favier, Thomas P Davis, Christopher Barnerkowollik, Martina H StenzelAbstract:Potential sources of inhibition have been investigated via in situ Fourier transform - near infra-red (FT-NIR) and off-line H-1 NMR spectroscopy in the RAFT/MADIX bulk polymerization of vinyl acetate (VA) in the presence of an O-isopropyl Xanthate, i.e. methyl (isopropoxycarbonothioyl)sulfanyl acetate. The very high reactivity of the vinyl acetate propagating radical makes it very vulnerable to oxygen, by-products generated during the Xanthate synthesis, and stabilizers present as impurities. These impurities induce strong and variable inhibition periods in the polymerization. In addition, the MADIX process, using Xanthates as reversible chain transfer agents, has been confirmed to be an efficient method for living VA polymerization. Congruent data are obtained when the monomer consumption with time is followed via both H-1 NMR and in situ FT-NIR spetroscopy. The Xanthate-mediated polymerization of VA exhibits no retardation effects and excellent control of the molecular weight distribution can be achieved, leading to poly(VA) of molecular weights exceeding 50 000 g . mol(-1) with relatively low polydispersities.
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a detailed on line ft nir and 1h nmr spectroscopic investigation into factors causing inhibition in Xanthate mediated vinyl acetate polymerization
Institute for Future Environments; Science & Engineering Faculty, 2004Co-Authors: Arnaud Favier, Thomas P Davis, Christopher Barnerkowollik, Martina H StenzelAbstract:Potential sources of inhibition have been investigated via in situ Fourier transform - near infra-red (FT-NIR) and off-line 1H NMR spectroscopy in the RAFT/MADIX bulk polymerization of vinyl acetate (VA) in the presence of an O-isopropyl Xanthate, i.e. methyl (isopropoxycarbonothioyl)sulfanyl acetate. The very high reactivity of the vinyl acetate propagating radical makes it vulnerable to oxygen, by-products generated during the Xanthate synthesis, and stabilizers present as impurities. These impurities induce strong and variable inhibition periods in the polymerization. In addition, the MADIX process, using Xanthates as reversible chain transfer agents, has been confirmed to be an efficient method for living VA polymerization. Congruent data are obtained when the monomer consumption with time is followed via both 1H NMR and in situ FT-NIR spectroscopy. The Xanthate-mediated polymerization of VA exhibits no retardation effects and excellent control of the molecular weight distribution can be achieved, leading to poly(VA) of molecular weights exceeding 50 000 g · mol-1 with relatively low polydispersities.
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Xanthate mediated living polymerization of vinyl acetate a systematic variation in madix raft agent structure
Macromolecular Chemistry and Physics, 2003Co-Authors: Martina H Stenzel, Lyndal Cummins, Evan G Roberts, Philipp Vana, Thomas P Davis, Christopher BarnerkowollikAbstract:Eight Xanthates were synthesized to induce living free radical polymerization of vinyl acetate. Four compounds, methyl (4-methoxyphenoxy)carbonothioylsulfanyl acetate, methyl (methoxycarbonothioyl)sulfanyl acetate, methyl (ethoxycarbonothioyl)sulfanyl acetate and methyl (isopropoxycarbonothioyl)sulfanyl acetate were identified as suitable MADIX/RAFT agents, yielding low polydispersity (PDI < 1.2) poly(vinyl acetate) of molecular weights exceeding 5 × 104 g · mol−1. All suitable MADIX/RAFT agents exhibited extended periods of inhibition (0.3 h < tinh < 10 h) and moderate rate retardation. The ability of these compounds to control vinyl acetate polymerization can be correlated with the electron density on the central carbon atom of the Xanthate. Electrospray ionization mass spectrometric analysis was performed to complete the investigation on the new MADIX/RAFT agents.
Samir Z Zard - One of the best experts on this subject based on the ideXlab platform.
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the Xanthate route to amines anilines and other nitrogen compounds a brief account
ChemInform, 2016Co-Authors: Beatrice Quicletsire, Samir Z ZardAbstract:An overview of a convergent, modular route to protected amines, anilines, and related compounds hinging on the degenerate radical addition-transfer of Xanthates is presented. Emphasis is placed on the importance of the stabilization of the starting radical by imides and other structures. 1 Introduction 2 The Degenerate Xanthate Transfer Process and Examples of Amine Synthesis 3 Stabilization of Radicals by Imides. Initial Observations and the Radical Aminomethylation of Alkenes 4 More Elaborate Phthalimide-Substituted Xanthates 5 Polyamines and β-Lactams 6 Anilines and Related Derivatives 7 Further Synthetic Variations 8 Outlook and Perspectives
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The Xanthate route to organofluorine derivatives. A brief account
Organic and Biomolecular Chemistry, 2016Co-Authors: Samir Z ZardAbstract:The present account summarises routes to organofluorine derivatives based on the chemistry of Xanthates developed in the author's laboratory. It concerns mostly radical pathways, but a few ionic transformations are also discussed. The degenerative reversible transfer of Xanthates allows radical addition even to unactivated alkenes and tolerates numerous functional groups, in particular common polar groups such as ketones, esters, amides, carbamates, nitriles etc. Since the fluorine atoms can be placed on the alkene or the Xanthate partner or on both, this opens a convergent approach to a vast array of otherwise inaccessible organofluorine structures that could be of interest to the pharmaceutical and agrochemical industries and to materials science.
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Radical Instability in Aid of Efficiency: A Powerful Route to Highly Functional MIDA Boronates
2015Co-Authors: Béatrice Quiclet-sire, Samir Z ZardAbstract:The inability of the sp3 boron in MIDA boronates to stabilize an adjacent radical makes possible the efficient addition of a wide array of Xanthates to vinyl MIDA boronate, leading to highly functionalized and diverse aliphatic organoboron structures. The lack of radical stabilization also allows the exchange of the Xanthate in the adducts with a bromine. In one case, the bromine was substituted to generate a cyclopropyl MIDA derivative
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the degenerative radical transfer of Xanthates and related derivatives an unusually powerful tool for the creation of carbon carbon bonds
Topics in Current Chemistry, 2006Co-Authors: Beatrice Quicletsire, Samir Z ZardAbstract:This review summarises recent work on the dithiocarbonyl group transfer reaction. Xanthates, in particular, have proved to be extremely useful for both inter- and intra-molecular additions. The broad applicability of the intermolecular addition to unactivated olefins opens tremendous opportunities for synthesis, since various functional groups can be brought together under mild conditions and complex structures can be rapidly assembled. The presence of the Xanthate in the product is also a powerful asset for further modifications, by both radical and non-radical pathways. Of special importance is the access to highly substituted aromatic and heteroaromatic derivatives and the synthesis of block polymers through a controlled radical polymerisation mediated by various dithiocarbonyl agents (RAFT and MADIX processes).
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a practical modification of the barton mccombie reaction and radical o to s rearrangement of Xanthates
Tetrahedron Letters, 1998Co-Authors: Beatrice Quicletsire, Samir Z ZardAbstract:Abstract The CO bond in Xanthates derived from carbohydrates can be reductively cleaved by heating in 2-propanol in the presence of equimolar amounts of dilauroyl peroxide, added in small portions; if benzene is used as the solvent, an O - to S - rearrangement of the Xanthate occurs.
Arnaud Favier - One of the best experts on this subject based on the ideXlab platform.
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a detailed on line ft nir and 1h nmr spectroscopic investigation into factors causing inhibition in Xanthate mediated vinyl acetate polymerization
Macromolecular Chemistry and Physics, 2004Co-Authors: Arnaud Favier, Thomas P Davis, Christopher Barnerkowollik, Martina H StenzelAbstract:Potential sources of inhibition have been investigated via in situ Fourier transform - near infra-red (FT-NIR) and off-line H-1 NMR spectroscopy in the RAFT/MADIX bulk polymerization of vinyl acetate (VA) in the presence of an O-isopropyl Xanthate, i.e. methyl (isopropoxycarbonothioyl)sulfanyl acetate. The very high reactivity of the vinyl acetate propagating radical makes it very vulnerable to oxygen, by-products generated during the Xanthate synthesis, and stabilizers present as impurities. These impurities induce strong and variable inhibition periods in the polymerization. In addition, the MADIX process, using Xanthates as reversible chain transfer agents, has been confirmed to be an efficient method for living VA polymerization. Congruent data are obtained when the monomer consumption with time is followed via both H-1 NMR and in situ FT-NIR spetroscopy. The Xanthate-mediated polymerization of VA exhibits no retardation effects and excellent control of the molecular weight distribution can be achieved, leading to poly(VA) of molecular weights exceeding 50 000 g . mol(-1) with relatively low polydispersities.
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a detailed on line ft nir and 1h nmr spectroscopic investigation into factors causing inhibition in Xanthate mediated vinyl acetate polymerization
Institute for Future Environments; Science & Engineering Faculty, 2004Co-Authors: Arnaud Favier, Thomas P Davis, Christopher Barnerkowollik, Martina H StenzelAbstract:Potential sources of inhibition have been investigated via in situ Fourier transform - near infra-red (FT-NIR) and off-line 1H NMR spectroscopy in the RAFT/MADIX bulk polymerization of vinyl acetate (VA) in the presence of an O-isopropyl Xanthate, i.e. methyl (isopropoxycarbonothioyl)sulfanyl acetate. The very high reactivity of the vinyl acetate propagating radical makes it vulnerable to oxygen, by-products generated during the Xanthate synthesis, and stabilizers present as impurities. These impurities induce strong and variable inhibition periods in the polymerization. In addition, the MADIX process, using Xanthates as reversible chain transfer agents, has been confirmed to be an efficient method for living VA polymerization. Congruent data are obtained when the monomer consumption with time is followed via both 1H NMR and in situ FT-NIR spectroscopy. The Xanthate-mediated polymerization of VA exhibits no retardation effects and excellent control of the molecular weight distribution can be achieved, leading to poly(VA) of molecular weights exceeding 50 000 g · mol-1 with relatively low polydispersities.
