Presence Of Acid Catalyst Research Articles

Chelating ion-exchange properties of 2-hydroxy-4-methoxyaceto-phenoneoxime-thiourea-trioxane resins

The resin (HMOTT') prepared by condensation of 2-hydroxy-4-methoxyacetophenoneoxime and thiourea with trioxane in the presence of acid catalyst, proved to be a selective chelating ion-exchange resin for certain metals. Chelating ion-exchange properties of this resin were studied for Cu 2+, Ni 2+, Co 2+, Mn 2+, Zn 2+, Fe 3+ and UO 2 2+ ions. A batch-equilibration method was employed in the study of the selectivity of metal-ion uptake involving the measurement of the distribution of a given metal ion between the resin sample and a solution containing the metal ion. The study was carried out over a wide pH range and in media of various ionic strengths. The resin showed a higher selectivity for Co 2+, Fe 3+ and UO 2 2+ ions than for Mn 2+, Co 2+ and Zn 2+ ions.

Study on ketalization reaction of poly(vinyl alcohol) by ketones. IV. Reaction between poly(vinyl alcohol) and aliphatic ketones and behavior of polyvinylketal in water

AbstractKetalization reaction of poly(vinyl alcohol) (PVA) by aliphatic ketones, dimethylsulfoxide (DMSO) as solvent, under the presence of acidic catalyst, in homogeneous system was carried out and the synthesis of polyvinylketals were successfully performed. The equilibrium constant at 40°C is ca. 0.07 in the case of methyl n‐propyl ketone (nPK) and methyl n‐butyl ketone (nBK), but is ca. 0.05 in the case of methyl i‐propyl ketone (iPK) and ca. 0.01 in the case of methyl i‐butyl ketone (iBK) and methyl t‐butyl ketone (tBK), respectively. Moreover, the ketalization degree of polyvinylketal by iBK and tBK reached to only ca. 35 mol % as the maximum. It seems that these were due to steric hindrance of bulky side chain of ketones. But the heat of reaction is 7.5 kcal/mol in all aliphatic ketones, it seems to proceed the same ketalization reaction mechanism. Films prepared from the polyvinylketals were soaked in water and degree of swelling, solubility, and hydrolysis of films were measured. The reaction of film with water, in acidic side, at first the film swells, and then, as the deketalization reaction proceeds, the film dissolves in water. The dissolution time is controlled by the kind of ketones, ketalization degree, and pH of water which reveals that deketalization reaction proceeds proportional to proton concentration. It is more difficult to dissolve highly ketalized polyvinylketals obtained by propyl ketones and butyl ketones than that by acetone. The hydrolysis of polyvinylketal film proceeds in the order as follows: acetone > MEK > nPK > iPK ≒ nBK > iBK > tBK. This phenomenon seems to be affected by hydrophobicity of the film surface which depends upon the kind of the original ketones.

ChemInform Abstract: Reaction of Hexamethyldisiloxane with 2‐Ethoxy‐1,3‐dioxolane.

AbstractThe reaction of hexamethyldisiloxane (II) with 2‐ethoxy‐1,3‐dioxolane to give the products (III) ‐ (VI) is studied in detail.

A Facile and Convenient Synthesis of (E,E)-4-Trifluoroacetyl-1,3-butadienyl Sulfides by Acid Catalyzed Reaction of 2,4-Diethoxy-6-trifluoromethyl-3,4-dihydro-2H-pyran with Thiols

Abstract (E,E)-4-Trifluoroacetyl-1,3-butadienyl sulfides are prepared from 2,4-diethoxy-6-trifluoromethyl-3,4-dihydro-2H-pyran with thiols in the presence of acid catalysts.

Reaction of hexamethyldisiloxane with 2-ethoxy-1,3-dioxolane

The reaction of hexamethyldisiloxane with 2-ethoxy-1,3-dioxolane is described. It is shown that cleavage of the endo- and exocyclic carbon-oxygen bonds of the ortho ester occurs under mild conditions (16–20‡C) in the presence of acidic catalysts with the formation of 2-(trimethylsiloxy)ethyl formate, the subsequent transformation of which leads to ethyl formate, trimethylethoxysilane, and 1,2-bis(trimethylsiloxy)ethane.

Salicylic acid‐biuret‐trioxane terpolymer resins and their ion‐exchange properties

AbstractTerpolymer resins (SBT) were synthesized by the condensation of salicylic acid and biuret with trioxane in the presence of acid catalyst and using varied molar ratios of reacting monomers. Terpolymer resin compositions have been determined on the basis of their elemental analysis and the number average molecular weights of these resins were determined by conductometric titration in non‐aqueous medium. The viscosity measurements carried out in DMF indicate normal behaviour. IR spectra were studied to elucidate the structure. TGA data were analysed to estimate the characteristic thermal parameters. The terpolymer resins have been further characterized by reflectance spectra in solid state, absorption spectra in non‐aqueous medium, X‐ray diffraction and electrical conductivity. Chelation ion‐exchange properties have also been studied employing the batch equilibration method.

Epoxy groups on grafted polypropylene. II. Reaction with amines

AbstractEpoxy groups attached to isotactic polypropylene in form of 2,3‐epoxypropylmethacrylate grafts were reacted with low molecular secondary amines. Secondary heterocyclic amines exhibit high reaction rates in this process. The bonding of less basic amines is accelerated in the presence of acid catalysts. The mechanism is discussed of amine‐acid couple influence upon the epoxy group present in heterogeneous system on the surface of solid polymer.

Improvement of various properties of fiber surfaces containing crosslinked polyethylene glycols

AbstractModification of a variety of fabric and fibrous surfaces was achieved by insolubilization thereon of crosslinked polythylene glycols (called POLYTHERM) to impart several useful properties: thermal storage and release, improved resiliency and resistance to oily soiling, static charge, pilling, wear life, and marked increases in hydrophilicity among them. Moreover, these improved properties were durable because up to 70% of the crosslinked polyol was retained after 50 launderings. Such modification was achieved by using average molecular weights of the polyols ranging from 600 to 20,000 by crosslinking with polyfunctional methylolamides (such as DMDHEU) in the presence of acid catalysts by a conventional pad‐dry‐cure textile finishing procedure. The role of crosslink density of the polyol in determining textile properties was determined by evaluation of films derived from crosslinking the polyols and comparison of selected properties.

Catalytic methods of synthesizing polybenzazoles. Review

The review is concerned with the analysis of the published data on the synthesis of polybenzazoles (polybenzoxazoles, polybenzimidazoles, polybenzthiazoles) in presence of acid catalysts. It is shown that all the main methods of synthesizing polybenzazoles — “Marvel reaction”, “Iwakura reaction” two-stage polycyclocondensation, high temperature polycyclocondensation in organic solvents, reductive polyheterocyclization—contain in themselves elements of catalytic polycyclocondensation. From a number of examples it is shown that the use of acid catalysts allows one not only to lower the temperature and shorten the duration of synthesis of the polybenzazoles but also to obtain polymers with an essentially new complex of properties.

Study on ketalization reaction of polyvinylalcohol by ketones. III. Reaction between polyvinylalcohol and methyl ethyl ketone and behavior of polyvinylketal in water

AbstractKetalization reaction of polyvinylalcohol (PVA) by methyl ethyl ketone (MEK), dimethyl‐sulfoxide (DMSO) as solvent, under the presence of acidic catalyst, in homogeneous system was carried out, and the synthesis of polyvinylketal with any ketalization degree was successfully performed. The reaction mechanism of PVA with MEK is identical with that with acetone: for both cases, the equilibrium constant is ca. 0.07 at 40°C and the heat of reaction is 7.5 kcal/mol. Films prepared from the polyvinylketal were soaked in water and degree of swell, solubility, and hydrolysis of films were measured. The reaction of film with water, in acidic side, easily proceeds, and at first the film swells; then, as deketalization reaction proceeds, the film dissolves in water. With polyvinylketal of the ketalization degree of above 15 mol %, dissolution time is controlled by both ketalization degree and pH of water, which reveals that deketalization reaction proceed proportionally to proton concentration at 37°C. On the other hand, in the neutral condition where hydrolysis does not proceed at all, polyvinylketal of ketalization degree of 10–40 mol % dissolves in water at 0°C. The polyvinylketal obtained by MEK is more stable in water than that from acetone since MEK has hydrophobicity.

ChemInform Abstract: Oxidative Rearrangement of Aryl Ethyl Ketones to Alkyl 2‐Arylpropanoates by Lead(IV) Acetate.

AbstractOxidative rearrangement of the propiophenones (I) in trialkyl orthoformate (II) proceeds via 1,2‐aryl migration to give the esters (III).

Solid-state polyamidation of hexamethylenediammonium adipate in the presence of acid catalysts. I. Preparation of the catalyst containing monomer

Journal of Polymer Science Part C: Polymer LettersVolume 25, Issue 9 p. 363-367 Article Solid-state polyamidation of hexamethylenediammonium adipate in the presence of acid catalysts. I. Preparation of the catalyst containing monomer Constantine D. Papaspyrides, Constantine D. Papaspyrides Laboratory of Special Chemical Technology, Department of Chemical Engineering, National Technical University of Athens, 42 Patission Street, Athens 106 82, GreeceSearch for more papers by this author Constantine D. Papaspyrides, Constantine D. Papaspyrides Laboratory of Special Chemical Technology, Department of Chemical Engineering, National Technical University of Athens, 42 Patission Street, Athens 106 82, GreeceSearch for more papers by this author First published: September 1987 https://doi.org/10.1002/pol.1987.140250901Citations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume25, Issue9September 1987Pages 363-367 RelatedInformation

Thermomechanochemical depolymerization of dextrans in aqueous phase

This article centers on the depolymerization of dextrans under the action of thermomechanical forces induced by rapid passage of concentrated dextran solutions through capillaries and homogenizing valves. Viscosity measurements combined with theoretical equations related to the properties of the dextran solutions led us to characterize the flexibility of dextrans chains in water. The influences of temperature and pressure gradient through the restrictions on the extent of depolymerization are described. The thermomechanical treatment is particularly effective in the presence of acid catalysts.

ChemInform Abstract: Anomeric Xanthates: A New Activation of the Anomeric Center for Rapid Glycosylation.

Abstract In recent years, glycosides, especially di- and oligosaccharides, have become substances of interest owing to their biochemical and pharmacological importance as antibiotics and antigens and many reports have appeared concerning the synthesis of these complex molecules1. Synthesis generally involved the preparation of two poly - functional partners; the hydroxyl component, prepared by selective blocking of a monosaccharide unit and the electrophilic partner, generated from an activated species. Various methods of activation of the anomeric center have been devised giving generally very good results. Oligosaccharides have been obtained from halogenoses, orthoesters2, imidates3, acetates4 in the presence of acidic catalysts or heavy metal salts5, as well as from thiomethyl glycosides as a glycosyl donor and methyl triflate or dimethyl-(methylthio)-sulfonium triflate as a promoter6. More complex heteroatomic activating groups have been developed such as N,N-dialkyldithiocarbamates7, phosphorodithioa...

Study on ketalization reaction of polyvinylalcohol by ketones. I. Reaction between polyvinylalcohol and acetone

AbstractKetalization reaction of polyvinylalcohol (PVA) by acetone, dimethylsulfoxide (DMSO) as solvent, under the presence of acidic catalyst, in homogeneous system was carried out and the synthesis of polyvinylketal with any ketalization degree was successfully performed. This reaction proceeds in bimolecular reaction, the equilibrium constant is ca. 0.07 at 40°C and roughly 10−5 less compared with the acetalization reaction between PVA and aldehydes. Synthesis in aqueous media is difficult. However, the heat of reaction for both cases is 7.5 kcal/mol and both reactions are considered to proceed in an identical reaction mechanism. Ketalization reaction starts from isotactic OH portion and proceeds finally to syndiotactic OH portion, however, 100% ketalization is extremely difficult. The effects of water on reaction was confirmed both from theoretical and experimental viewpoints, and even though the presence of water lowers the degree of ketalization, it was observed that the presence of water below 0.1 mol against 1 mol of PVA will not significantly affect final ketalization degree. Polyvinylketals thus obtained are soluble in DMSO, dimethylformamide (DMF), and alcohols.

Reverse osmosis and fine structure of decrystallized acrylic acid grafted nylon 6 membranes

AbstractNylon 6 film and acrylic acid grafted nylon 6 (GN) membrances were reacted with paraformaldehyde and lactic acid in the presence of acid catalysts. Decrystallized nylon 6 (DN) and decrystallized grafted nylon 6 (DGN) membranes were thus obtained. The cross sections of GN and DGN membranes were observed by a transmission electron microscope. Branch poly(acrylic acid) penetrated toward the center of the membrane and deposited homogeneously within the membrane as the extent of grafting exceeded about 100%. The reverse osmosis of DN and DGN membranes was investigated. The water permeability through the membranes was improved by the decrystallization reaction. DGN membranes with more than 100% grafting show high values of the salt rejection (Rs) as compared with DN and DGN membranes with about 50% grafting, especially at the region of the high hydraulic permeability coefficient of water (K). The relationships among Rs, K, and the volume fraction of water (H) are discussed by considering the results of the decrystallization reaction and electron microscopy.

Oxidative rearrangement of aryl ethyl ketones to alkyl 2-arylpropanoates by lead(IV) acetate

Treatment of the propiophenones p-R′C6H4COCH2Me (1; R′= H, Me, Bui, Ph, Br) with lead(IV) acetate in trialkyl orthoformate in the presence of acid catalyst is found to give alkyl esters of 2-arylpropanoic acids (2) in good to excellent yields via 1,2-aryl migration in (1). Hydrolysis of (2) leads to the corresponding acids, some of which are important pharmaceutical compounds. The rate of aryl migration increases when the substituent R′ is an electron-releasing group such as methyl, isobutyl, or phenyl. The rate of rearrangement of the dimethyl acetals of (1; R′= H, Bui, Ph) is nearly the same as that of (1). Such rearrangement hardly occurs in the absence of acid catalyst. A reaction pathway involving the formation of a monoalkoxylead(IV) compound, and its decomposition accompanied with aryl migration is discussed.

Anomeric Xanthates: A New Activation of the Anomeric Center for Rapid Glycosylation

Abstract In recent years, glycosides, especially di- and oligosaccharides, have become substances of interest owing to their biochemical and pharmacological importance as antibiotics and antigens and many reports have appeared concerning the synthesis of these complex molecules1. Synthesis generally involved the preparation of two poly - functional partners; the hydroxyl component, prepared by selective blocking of a monosaccharide unit and the electrophilic partner, generated from an activated species. Various methods of activation of the anomeric center have been devised giving generally very good results. Oligosaccharides have been obtained from halogenoses, orthoesters2, imidates3, acetates4 in the presence of acidic catalysts or heavy metal salts5, as well as from thiomethyl glycosides as a glycosyl donor and methyl triflate or dimethyl-(methylthio)-sulfonium triflate as a promoter6. More complex heteroatomic activating groups have been developed such as N,N-dialkyldithiocarbamates7, phosphorodithioates8 and 2-benzothiazolyl9 derivatives, the latter providing an efficient glucosylation method.

Products characterization of tung oil–phenol reactions based on analysis of a model reaction

AbstractA method of determining the molecular species composition distributions of products obtained by reaction of tung oil with various phenols in the presence of acid catalyst has been studied. Methyl α‐eleostearate was used as a model substance in place of tung oil. The product composition analysis of methyl α‐eleostearate reactions with phenols was done by HLC. From these results, the molecular weight distributions and molecular species composition distributions of the reaction products were calculated according to a statistical procedure. Good agreement was found between the calculated and experimental molecular weight distribution, which enabled prediction of the molecular species composition distribution.

Influence of acid catalysts on the solid-state polyamidation of dodecamethylenediammonium adipate

Solid-state polyamidation is an alternative route for polyamide synthesis. Solid-state polyamidation of dodecamethylenediammonium adipate was studied in the presence of acid catalysts. Boric acid proved to be the most effective catalyst, followed by sulphuric acid, so that—even at high reaction rates—the reaction was maintained in the solid state throughout the process. On the other hand, phosphoric acid showed a clearly weaker action resulting eventually in a transition of the process from the solid to the melt state, in accordance with noncatalysed behaviour. In general, catalyst concentration plays a considerable role in the catalytic effectiveness obtained.