Download or read book Soluble Polymer supported Catalysts and Initiators written by Uche K. Anyanwu and published by . This book was released on 2005 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies of Soluble Polymer supported Organocatalysts written by Yun-Chin Yang and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer-supported reagents and catalysts have been extensively studied in the past few decades as they not only facilitate separation and isolation of products after reactions but also enable reuse of reagents/catalysts. In particular, chemistry using polymer-supported organocatalysts has the advantage of avoiding the use of sometimes toxic transition metals. Since organocatalysts are often used at high mol% loading in catalytic reactions, immobilizing organocatalysts on polymers for recycling and reusing makes chemistry using organocatalysts attractive in larger scale syntheses. Chapter II of this dissertation focuses on using variable temperature 31P NMR spectroscopy to study and compare the dynamic behavior of silver complexes prepared from soluble polymer-supported phosphines and electronically similar low molecular weight phosphine ligands. The phosphine-silver complexes supported on terminally functionalized polyisobutylene (PIB) and poly(ethylene glycol) show similar kinetic behavior compared to their low molecular weight counterparts. However, the dynamic behavior of phosphine-silver complexes supported as pendent groups on a linear polystyrene is difficult to study because of significant line-broadening on 31P NMR spectra. Chapter III of this dissertation aims at examining the recyclability and reusability of PIB-supported phosphines as organocatalysts and reagents. PIB-supported alkyldiphenyl- and aryldiphenylphosphines were prepared and used as recyclable organocatalysts in addition and allylic amination reactions. The PIB-bound phosphines were useful reagents in aza-Wittig and Mitsunobu reactions. The PIB-bound phosphine oxides formed either from adventitious oxidation or during the course of reactions can be reduce to PIB-phosphines for reuse. Chapter IV of this dissertation describes preliminary studies on soluble polymer-supported N-heterocyclic carbene (NHC) organocatalysts. PIB- and polyethylene oligomer (PE_Olig)-supported NHC adducts were synthesized and the corresponding polymer-supported NHC catalysts were generated in situ in lactide polymerization and phenyl isocyanate trimerization reactions. The PIB-bound NHC catalyst generated in situ was not recyclable in a lactide polymerization. However, PIB- and PEOlig-bound NHC precatalysts showed modest recyclability in lactide polymerization and phenyl isocyanate trimerizations.
Download or read book Polymeric Materials in Organic Synthesis and Catalysis written by Michael R. Buchmeiser and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 582 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book to describe the synthesis and characterization of the materials used in polymer-supported synthesis. The authors cover not only the classical polymers and their use in homogeneous, heterogeneous and micellar catalysis, but also such new developments as "enzyme-labile linkers", illustrating how to simplify the purification process and avoid waste. The result is a wealth of useful information -- for beginners and experts alike - in one handy reference, removing the need for difficult and time-consuming research among the literature.
Download or read book Supported Catalysts from Polymers to Gold Nanoparticles Supports written by William J. Sommer and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In today's world, the need to limit the use of nonrenewable resources and the importance of recycling has been recognized. One important contribution of chemists toward the general goal of limiting their use is to find catalysts that can be reused and recycled thereby limiting the need for expensive metal precursors and metal waste. Strategies to recycle catalysts are multifold and range from the employment of soluble polymers as catalyst supports to the use of membrane-encapsulated catalyst. The use of soluble polymers as a support not only offers the advantage of being soluble under the catalytic reaction conditions but also, to be removable by changing the conditions of the surrounding media. Despite the great potential of these soluble supported catalysts, their use is very limited in today's synthesis. In addition, no set of rules have been established to guide the synthesis of efficient supported catalysts. In order to establish a "tool box" for the synthesis of supported catalysts, the study of several parameters such as the choice of the support and the choice and the stability of the catalyst are necessary. To establish this set of rules, a limited number of catalytic transformations, were studied. These catalytic reactions are the Heck-Mizoroki, Suzuki-Miyaura and Sonogashira coupling reactions. These transformations became fundamental for the synthesis of drugs and materials. The first and second chapters provide background information by describing and evaluating the main supports that were previously used for catalysts and the two main catalysts that are used in this thesis, the palladium pincer complex and the palladium N-heterocyclic complex. In chapter 3, the synthesis of a soluble polymer supported catalyst is described. The polymer chosen for the study is poly(norbornene), and the catalyst is a 1,3-disubstituted benzene ligand with sulfurs in the side-chains able to chelate to the metal center, better known as pincer ligand. These ligands are abbreviated by the three atoms that coordinate to the metal center, in this study, SCS. The metal used for the investigation of the activity of this supported pincer is palladium. The importance of the nature of the linkage on the stability of the Pd-SCS pincer complex has been reported in the literature, leading to the synthesis of Pd-SCS pincer complex tethered to the polymer via an ether and an amide linkage. The synthesized poly(norbornene) supported Pd-SCS pincer complexes were evaluated using the Heck transformation of iodobenzene with n-butyl acrylate. Kinetic studies and leaching tests using poly(vinyl pyridine) and mercury were carried out resulting in the conclusion that the active species during the catalysis is not the palladium pincer complex but a leached palladium (0) species. In chapter 4, Pd-PCP pincer complexes with the ether and amide tether were synthesized. Kinetic and poisoning studies were carried out resulting in a similar conclusion. Furthermore, 31P NMR experiments were conducted to investigate the unstability of the complex. Following this study, in-situ XAS as well as computational calculations were carried out. The conclusion from this investigation argues that triethylamine is a key ingredient for the decomposition of the Pd-PCP complex. The overall conclusion from these two different studies is thta Pd(II) pincer complexes decomposes during the Heck reaction when triethylamine is used for the coupling of iodobenzene to n-butyl acrylate in DMF at 120°C. Stemming from this investigation, a reported more stable complex, Pd-NHC, was tethered onto poly(norbornene). The system was evaluated using Suzuki-Miyaura, Heck and Sonogashira reactions. Similar poisoning and kinetic studies were utilized to investigate the stability of the supported NHC Pd complexes. The result of this investigation suggests that supported Pd-NHC complexes are stable under Suzuki-Miyaura and Sonogashira but decompose under Heck conditions. However, when the system was recycled, a decrease in activity for the Suzuki-Miyaura transformation and solubility was observed. In chapter 6, gold monolayer protected clusters (MPC) were investigated as potential candidates as supports. To examine the potential of MPC as a support, a NHC-Pd complex was graphted onto the particles. To functionalize the gold nanoparticles, a new method was developed. Using azide moieties added to the gold nanoparticles, the catalyst was added via microwave assisted 1,3 dipolar cycloaddition. The system was evaluated using Suzuki-Miyaura transformations under microwave conditions. The system exhibited quantitative conversions for a variety of substrates. However, when the system was recycled, aggregation of the particles and decrease in catalytic activity was observed. In summary, this thesis describes the synthesis and evaluation of poly(norbornene) supported Pd-pincer and Pd-NHC complexes and of gold nanoparticles supported Pd-NHC complex. It also detail the combination of kinetic and poisoning studies developed to evaluate a potential supported catalyst.
Download or read book Polymer Supported Organic Catalysts written by Narendra Chauhan and published by CRC Press. This book was released on 2024-07-26 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer-supported organic catalysts are largely insoluble in most reaction solvents, which allows for easy recovery and recycling of the catalysts. They are generally stable, readily available, and environmental friendly, so they have attracted the interest of many synthetic chemists in the industrial and academic fields. In this book, different types of polymer-supported catalysts based on peptides, polystyrene, polyethers, poly(acrylic acid), poly(ethylene imine), poly(2-oxazoline), poly(isobutylene), poly(norbornene), etc., as well as metals are included with their synthetic organic synthesis applications. It is believed that this work will be of interest to organic chemists, material scientists, chemical engineers, polymer scientists and technologists.
Download or read book Immobilized Catalysts written by Andreas Kirschning and published by Springer Science & Business Media. This book was released on 2004-11-22 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: R. Haag, S. Roller: Polymeric Supports for the Immobilisation of Catalysts .- J. Horn, F. Michalek, C.C. Tzschucke, W. Bannwarth: Non-Covalently Solid-Phase Bound Catalysts for Organic Synthesis .- Y. Uozumi: Recent Progress in Polymeric Palladium Catalysts for Organic Synthesis .- D.E. Bergbreiter, J. Li: Applications of Catalysts on Soluble Supports .- B. Desai, C.O. Kappe: Microwave-Assisted Synthesis Involving Immobilized Catalysts .- A. Kirschning, G. Jas: Applications of Immobilized Catalysts in Continuous Flow Processes .- N. End, K.-U. Schöning: Immobilized Catalysts in Industrial Research and Application .- N. End, K.-U. Schöning: Immobilized Biocatalysts in Industrial Research and Production
Download or read book Polymer Supported Chemical Reactions written by P. Hodge and published by iSmithers Rapra Publishing. This book was released on 1991 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer supported chemical reactions may include those using supported substrates, reagents and catalysts, and this report describes all three types. In all cases the most frequent reason for the use of a polymeric support will be the ease of separation of the supported and the low molecular c099 species. An additional indexed section containing several hundred abstracts from the Rapra Polymer Library database provides useful references for further reading.
Download or read book Hairy Particles written by Xiaoming Jiang and published by . This book was released on 2010 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the synthesis and studies of polymer brush-supported organocatalysts and asymmetric mixed homopolymer brushes grafted on particles. The brushes were synthesized from initiator-functionalized particles by surface-initiated "living" radical polymerizations. Polymer brush-supported organocatalysts were designed to combine the advantages of both soluble polymer- (high activity) and crosslinked insoluble polymer-supported catalysts (recyclability). Chapter 1 describes the synthesis of a polymer brush-supported 4-N, N-dialkylaminopyridine (DAAP) catalyst from initiator-functionalized latex particles by surface-initiated nitroxide-mediated radical polymerization (NMRP). The hairy particles efficiently catalyzed the acylation of secondary alcohols and Baylis-Hillman reaction and were recycled [greater or lesser than] six times with no or negligible decrease in the reaction yield. Chapter 2 presents the synthesis of a thermosensitive polymer brush-supported DAAP by surface-initiated atom transfer radical polymerization (ATRP) from silica particles with addition of a free initiator. Both hairy particles and the free copolymer formed from the free initiator were used as catalysts for hydrolysis of nitrophenyl acetate at various temperatures. Below the lower critical solution temperature (LCST), the activity of hairy particles was very close to that of the free copolymer. LCST transitions exerted different effects on the reactions catalyzed by hairy particles and the free copolymer. Chapters 3 and 4 present the studies of the effects of chain length disparity and grafting density on phase morphology of mixed brushes grafted on silica particles. A series of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes with a fixed PtBA molecular weight and various PS molecular weights were grown from silica particles functionalized with a monochlorosilane-terminated asymmetric difunctional initiator (Y-initiator) by sequential ATRP and NMRP. The total grafting densities of these brushes were 0.6 -- 0.7 chains/nm2. The morphology of mixed brushes evolved from isolated PS nanodomains, to short PS cylinders, to a nearly bicontinuous nanostructure, and a two-layered nanostructure with the change of chain length disparity of two homopolymers. To study the grafting density effect, a set of high density asymmetric mixed brushes with total grafting densities of 0.9 -- 1.2 chains/nm2 was prepared from triethoxysilane-terminated Y-initiator-functionalized silica particles. The feature sizes of the patterns formed from high density mixed brushes were much smaller than those of lower density mixed brushes.
Download or read book Phase Selectively Soluble Polymers for Homogeneously Supported Catalysts written by Shayna D Sung and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Soluble polymer supports that could be used in thermomorphic and latent biphasic systems have been prepared and analyzed for their potential application as supports for facilitated synthesis and catalysis. Phase selective solubilities were evaluated using polymers tagged with either visible dyes or fluorescent probes. Heptane/DMF, heptane/90% ethanol-water, heptane/ethyl acetate, heptane/ ethanol and heptane/tert-butanol solvent mixtures were all studied as examples of thermomorphic orlatent biphasic systems. A range of polymers, including poly-(tert-butylstyrene)(PTBS), poly(alkylsiloxanes) (PAS), poly(dodecylvinylpyrrolidone) (PDVP), poly(didodecylvinylpyrrolidone (PDDVP), poly (isobutylene) (PIB), poly (octadecylacrylate)s (PODA), and poly(octadecyl methacrylate)s (PODMA), were tested for hydrophobic phase selective solubility. The results of these studies were compared to prior work with polar and nonpolar poly (N-alkylacrylamide)s and polystyrene. Together with this prior work, these results have indicated that a wide range of polymers and solvent mixtures can be used for the recycling of soluble polymer-bound catalysts, reagents and sequestrants using either thermomorphic or latent biphasic separation strategies. Synthetic routes to terminally functionalized polyisobutylene oligomers, usefulas supports in synthesis and catalysis, are also discussed and described. Suchhydrocarbon polymers serve as highly soluble nonpolar analogs of well known poly(ethylene glycol) supports for synthesis and catalysis with the difference that the polymers are separated after a reaction by an extraction with alkane solvent. The synthesis of two polyisobutylene-supported phase transfer catalysts (PTC)are also described. These PTCs utilize the robust triazole functionality as a key synthetic step towards the preparation of the catalytic species. N alkylation of a PIB-supported triazole provides a direct route to the preparation of a PTC. Preparation of a tertiary phosphoninium salt containing a terminal alkyne allows simple attachment of the PTC to a PIB-supported azide via a triazole linker using Sharpless' Cu (I) [3 + 2] cycloaddition. These materials are active in catalyzing solid-liquid PTC and can be easily recycled by liquid-liquid extraction techniques.
Download or read book Supported Aqueous phase Catalysis for Atom Transfer Radical Polymerization written by Ravi Aggarwal and published by . This book was released on 2010 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atom transfer radical polymerization (ATRP) which utilizes transition metal based catalysts is a versatile methodology for the synthesis of a wide spectrum of polymers with controlled architectures. However, high concentrations of soluble catalyst required in an ATRP process makes the final polymer colored and toxic. Thus, the catalyst removal/reduction/recycling remains a challenge in the field of ATRP. Supported catalysts on insoluble solids such as silica gel, polystyrene beads, etc. have been used in ATRP to facilitate the catalyst recovery and recycling. However, the ability of the supported catalysts to mediate a polymerization is substantially reduced due to their reduced mobility and leaching problems. In this thesis, we report a series of novel and recyclable physisorbed CuBr2/N, N, N', N'' -pentamethyldiethylene-triamine supported catalytic systems operating in conjunction with hydration. Supported aqueous-phase catalysis (SAPC) for ATRP was evaluated for different inorganic (Na-clay, silica and zeolite) and organic (polysaccharides) supports. The hydrated physisorbed supported catalysts were used for the polymerization of benzyl methacrylate and methyl methacrylate using an activator generated electron transfer ATRP process. The catalyst was effectively retained on the surface of supports through hydration as was verified by UV-Vis measurements. The supported catalyst was easily removed from the polymerization by simple filtration process affording a colorless polymer solution. The polymerizations produced high conversion and colorless polymers with moderately narrow polydispersity indices (PDI). The catalyst maintained high activity during the recycling experiments. We also investigated the kinetic and mechanistic behavior of these solid supported polymerization systems. Based on split kinetics experiments and UV-Vis studies it was believed that the activation and deactivation processes took place at the diffused hydrated interface between the solid support and organic phase. The branched (stars and graft) polymers were also synthesized using Na-clay supported catalyst. The produced polymers had narrow PDI and good initiator efficiencies. The functionality of the star polymers was confirmed using 1H NMR and dilute solution properties. The synthesis of graft-copolymer was confirmed by 1H NMR and atomic force microscopy. This thesis demonstrates the successful use of SAPC for ATRP to produce contamination free linear and branched polymers with moderately narrow PDI and high recycling efficiency.
Download or read book The Use of Soluble Polymer supports in Catalysis and Synthesis written by Yunshan Liu and published by . This book was released on 1998 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Selection of a soluble polymeric support for the Wilkinson catalyst written by Charles Cross Wear and published by . This book was released on 1977 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polymeric Reagents and Catalysts written by Warren T. Ford and published by . This book was released on 1986 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Examines recent advances in the use of polymeric reagents and catalysts with a special emphasis on new compounds, synthetic methods, and industrial processes. Brings these advances to the attention of those who are involved in organic synthesis and desire a more thorough understanding of polymers and polymeric reagents. Contains comprehensive chapters devoted to polymeric oxidizing agents, Wittig reagents, and synthesis of cross-linked polymeric templates for chiral recognition. Presents opportunities for invention and use of many new polymeric reagents and catalysts.
Download or read book Crown Ethers and Phase Transfer Catalysis in Polymer Science written by Lon J. Mathias and published by Springer. This book was released on 1984-02 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase transfer catalysis or interfacial catalysis is a syn thetic technique involving transport of an organic or inorganic salt from a solid or aqueous phase into an organic liquid where reaction with an organic-soluble substrate takes place. Over the past 15 years there has been an enormous amount of effort invested in the development of this technique in organic synthe sis. Several books and numerous review articles have appeared summarizing applications in which low molecular weight catalysts are employed. These generally include either crown ethers or onium salts of various kinds. While the term phase transfer catalysis is relatively new, the concept of using a phasetrans fer agent (PTA) is much older~ Both Schnell and Morgan employed such catalysts in synthesis of polymeric species in the early 1950's. Present developments are really extensions of these early applications. It has only been within the last several years that the use of phase transfer processes have been employed in polymer synthesis and modification. Similarly, the use of polymer-bound phase transfer agents is also a recent development. These and related areas have nonetheless enjoyed explosive growth as mea sured by the number of publications and the variety of applica tions which have appeared. Several reviews dealing with these l 6 polymer-related investigations have been published.
Download or read book Coordination Polymerization written by Charles C. Price and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edwin J. Vandenberg, a long time researcher at the Research Center of Hercules Incorporated, was the 1981 winner of the American Chemical Society Award in Polymer Chemistry, sponsored by the Witco Chemical Corp. Following is the citation of the accomplishments which led to this award. "In recognition of his pioneering research that advanced polymer science and that led to the discovery and development of isotactic polypropylene, epichlorohydrin and propylene oxide elastomers, new polymerization catalysts, and the hydrogen method of controlling molecular weights of Ziegler polyolefins." It was my pleasure to arrange a symposium to celebrate this award at the Atlanta Meeting of the American Chemical Society on March 30, 1981. In considering the broad range of Vandenberg's contributions to polymer chemistry, it was decided to choose the subject of "Coordination Polymerization" for the symposium. This area is both one to which Vandenberg has made major contributions and one of great industrial and scientific interest. Since Vandenberg has been involved in coordination polymerization in both ring-opening and a-olefin type polymerizations, both were covered in the symposium, whose program follows. 1. "The Polymerization of 1,2-Epoxides Catalyzed by the Condensation Products of Metal-Containing Compounds with Alkylphosphates", T. Nakata, Research Laboratories, Osaka Soda Co., Ltd., 9 Otakasu-cho, Amagasaki City, Hyogo Pref. 660, Japan.
Download or read book Ring Opening Metathesis Polymerisation and Related Chemistry written by Ezat Khosravi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the last ASI in Turkey in Sept. 1995, the olefin metathesis has made remarkable strong developments with an incredible speed in various directions. New catalyst systems have been developed which have resulted in the synthesis of novel materials. Other fascinating developments have been the new catalysts for stereoselective metathesis and catalysts with considerable functional group tolerance. These new catalysts in addition to Ring Opening Metathesis Polymerisation (ROMP) and Acyclic Diene Metathesis (ADMET) are now powerful tools for Ring Closing Metathesis (RCM) and have found many applications in the synthesis of natural products. A lot of information has been established about all aspects of the olefin metathesis and there is a vast literature concerning the process, covering the initiators, mechanistic features and applications of this reaction in organic and polymer synthesis. The NATO ASI on rd th ROMP and Related Chemistry took place in Polanica-Zdroj, Poland during 3 to 15 Sept. 2000, to highlight the developments in this area and to discuss the prospects and visions for the year 2000 and beyond. The aims of the ASI were: to provide a platform for dissemination of knowledge; to promote communication between people who have a serious interest in this field of chemistry; to help establishing international scientific contacts and to provide an opportunity for the scientists with an appropriate scientific background to learn of recent developments in this field of science. There were 15 lecturers and 67 participants in this NATO ASI.
Download or read book Polymer supported Catalysts written by LeRoy Carl Kroll and published by . This book was released on 1974 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:
