Lamellar zirconium phosphonates containing pendant sulphonic acid groups

The versatile sulphonic acid group has been introduced into the family of interlamellar anchored materials. Zirconium bis-3-sulphopropylphosphonate is an example of an aliphatic acid. Zirconium bis-2-(sulphophenyl)ethylphosphonate is an example with an aromatic sulphonic acid group. In general, the sulphonic acids are not as crystalline as the carboxylic acid analogs. This is probably due to the relatively large size of the sulphonic acid group compared to the available cross sectional area of the layer face. The aliphatic compounds are more crystalline than the aromatics, as is expected from size considerations. The sulphonic acid group in both crystalline and semi-crystalline examples is accessible to reaction with bases. A few preliminary experiments have demonstrated the utility of these compounds as both strong acid ion exchangers and Bronsted acid catalysts. The layered sulphonic acid—zirconium 3-sulphopropylphosphonate—is thermally stable to well over 200°C. This indicates good potential for applications in Bronsted catalysis. This stability compares favorably with organic resin based sulphonic acids.The sulphonic acid class of interlamellar anchored materials have now been established. Both aliphatic and aromatic examples have been prepared. The utility of the sulphonic acids has been demonstrated with the typical reactions of this functional group. Specifically, the acids have been shown to be strong acid cation exchangers and a Bronsted acid catalyst. In addition, we have begun to develop an insight into the structural ramifications of these compounds. The size constraints of the zirconium phosphate type backbone are evident. Further, the thermal stability of this group of compounds is encouraging relative to its applications potential.     

Mass spectral fragmentation pattern of 2,2′-bipyridyls. Part VIII. 2,2′-Bipyridyl-5-carboxylic Acid and 2,2′-bipyridyl-5-sulphonic acid

The mass spectra of 2,2′-bipyridyl-5-carboxylic acid and 2,2′-bipyridyl-5-sulphonic acid obtained by electron impact are described. The principal initial fragmentation routes from the molecular ion of the carboxylic acid involve loss of CO, CN^˙, HCN, CO₂, OH^˙ and H₂O. From the molecular ion of the sulphonic acid the principal fragmentations are accompanied by loss of HCN, O₃, SO₂ and SO₃.     

Ion pair chromatography on reversed-phase layers

The results of investigations with ion pair chromatography on RP₂, RP₈ and RP₁₈ thin layers are described. Heptane sulphonic acid is used as ion pair former. The best results are achieved on RP₁₈-layers with the counter ion in the mobile phase.     

The Chromatographic Behavior of some Hydrophilic Dyes and Dye Intermediates on Thin Layers of Strong and Weak Ion Exchangers

Abstract

The chromatographic behavior of some polar organic dyes and dye intermediates on thin layers of various forms of cationic and anionic exchange resins has been investigated. The results of this study indicate that the stationary ion and the mobile ion of both types of exchangers greatly affect both the level of tailing and the R_f values of the adsorbed compounds. It is also clear from this study that these resins are more suitable for evaluating the relatively simple dyes containing an SO₃Na group than the higher molecular weight polyazo direct dyes used on cellulosic substrates, and that the Li⁺ and H⁺ forms of the cation exchangers work better than their counterparts. On the other hand, cationic dye molecules require the use of anion exchangers, with the ^?OAc form giving better chromatograms than the C104^? form.     

Thermoreversible polyaniline gels

Polyaniline (PANI) forms thermoreversible gels in different sulphonic acids e.g. dinonyl napthalene sulphonic acid (DNNSA), dinonylnapthalene disulphonic acid (DNNDSA), ± camphor ‐ 10 ‐ sulphonic acid (CSA) and dodecyl sulphonic acid (DSA) when processed from the formic acid medium. The surfactant concentration has been varied from weight fraction of PANI (W_PANI)=0.05−0.60. In most cases at W_PANI=0.05−0.40 compositions fibrillar network structures are observed from SEM study. They also exhibit reversible first order phase transition during both heating and cooling in DSC. The melting temperature and the gelation temperature increases with increase in surfactant concentration of the gel. From the WAXS pattern it is concluded that crystallization of the surfactant tails anchored from the nitrogen atom of PANI through its SO₃ H head group is responsible for gelation. The conductivity of all the gels with increase in PANI concentration showed a maximum with composition. The maximum conductivity is ∼0.01 S/cm, for W_PANI=0.22. The conductivity variation has been explained by considering it as a function of both interchain and intrachain contributions.     

Mass spectral studies of alkylbenzenesulphonic acids through their S-benzylisothiouronium salts

The mass spectra of alkylbenzenesulphonic acids in the form of their S-benzylisothiouronium salts have been studied. These S-benzylisothiouronium salts dissociated into two parent reactant ions: (i) alkylbenzenesulphonic acid and (ii) S-benzylisothiourea. The characteristic fragmentation patterns of alkylbenzenesulphonic acids (0-5 substituted alkyls) were studied and compared with those of the parent hydrocarbons. The intensity of the molecular ion peak decreased with the increase in the molecular weight of the sulphonic acids. Desulphonation as well as loss of the alkyl group was observed in all the spectra. Migration of the alkyl group from S to O, followed by degradation, was also observed in all the spectra studied.     

1,3-THIAZOLIDINIC AND 2,4,5,6-TETRAHYDRO-1,3-THIAZINIC SPIROCHROMENES AND MEROCYANINES. SYNTHESIS,REACTIVITY AND PHOTOCHROMIC PROPERTIES

Abstract

The acid catalyzed rate for hydrolysis of methylphosponfluoridic acid has been determined at several hydrogen ion concentrations and temperatures. The acid hydrolysis is second order (in acid and substrate). Assumed rate expressions, observed rate constants, and hydrogen ion concentrations were used to calculate the thermodynamic equilibrium constant (K _a=0.56) and rate constants for acid catalysis. The activation energy E _a has been determined as 18.3 Kcal/mole. Finally, the acid catalyzed deuterolysis was determined to be about 1.47 times the rate of hydrolysis. The data suggest a two-step mechanism consisting of a rapid proton transfer, followed by slow hydration of the protonated complex.     

Modelling free-radical copolymerization kinetics—evaluation of the pseudo-kinetic rate constant method, 1. Molecular weight calculations for linear copolymers

The moment equations for binary copolymerization in the context of the terminal model have been solved numerically for a batch reactor operating over a wide range of conditions. Calculated number- and weight-average molecular weights were compared with those found using pseudo-kinetic rate constants with the method of moments and with the instantaneous property method for homopolymerization. With the pseudo-kinetic rate constant method under polymerization conditions where number-average molecular weights (M̄_n) are below about 10³ the error in calculating M̄_n exceeds 5%. The error increases rapidly with decrease in molecular weight for M̄_n < 10³. M̄_n measured experimentally for polymer chains (homo- and copolymers) have error limits of greater than ±5% at the 95% confidence level. Therefore, for all practical purposes, the pseudo-kinetic rate constant method is valid for M̄_n greater than 10³. Errors in calculating weight-average molecular weights (M̄_w) or higher averages are always smaller than those for M̄_n when applying the pseudo-kinetic rate constant method. The assumptions involved in molecular weight modelling using the pseudo-kinetic rate constant approach are thus proven to be valid, and therefore it is recommended that the pseudo-kinetic rate constant method be employed with the instantaneous property method to calculate the full molecular weight distribution and averages for linear chains synthesized by multicomponent chain growth polymerization.     

A model study for coatings containing hexamethoxymethylmelamine

Using a model reaction we have studied the crosslinking chemistry of hydroxy-functional polymers and hexamethoxymethylmelamine. The transetherification of optically active monofunctional alcohols and hexamethoxymethylmelamine was monitored with polarimetry and ¹H-NMR. The reaction rate constants for both the forward (k₁) and the backward (k_?1) reaction of the sulphonic-acid-catalyzed alcoholysis were determined. Primary and secondary alcohols showed the same reaction rate and activation energy (E_a = 96 kJ/mol) for the forward reaction. However, the backward reaction in the equilibrium is considerably slower for primary alcohols than for secondary alcohols, with activation energies of E_a = 96 and 79 kJ/mol, respectively. When amine salts of sulphonic acids are used as catalysts, the E_a is increased from 97 to 116 kJ/mol in the case of primary alcohols. In concentrated aprotic solutions the reaction order in acid is 2.5. The same order in acid is found for the alcoholysis of acetaldehyde diethyl acetal. All the results strongly support the statement that the crosslinking reaction proceeds by an Sn-1 mechanism. The results of this model study are compared with results obtained in network-forming reactions. The important role of the evaporation of the condensation product methanol is discussed.     

Liquid secondary ion mass spectrometry analysis of permethylated,n-hexylamine derivatized oligosaccharides. Application to baculovirus expressed mouse interleukin-3

Reductive amination with n-hexylamine followed by permethylation was used as a procedure for the liquid secondary ion mass spectrometry (LSIMS) analysis of Asn-linked oligosaccharides. Initial experiments with this procedure were performed on maltoheptaose. These experiments show that exhaustive methylation at the newly formed secondary nitrogen forms a quaternary ammonium salt. When this is subjected to positive ion LSIMS, an abundant M⁺ ion is observed. This procedure was applied to the Asn-linked oligosaccharides released from human transferrin and ribonuclease-B. The reductively aminated, permethylated mixture of oligosaccharides from ribonuclease-B afforded a positive ion LSI mass spectrum in which M⁺ ions for Mans_5–9GlcNAc₂ could be assigned. The positive ion LSI mass spectrum obtained from the mixture of oligosaccharides isolated from human transferrin showed M⁺ ions that could be assigned to both monosialylated and disialylated biantennary complex type oligosaccharides. Reductive amination followed by permethylation of the Asn-linked oligosaccharides isolated from baculovirus expressed mouse interleukin-3 produced in Bombyx mori gave a positive ion LSI mass spectrum in which the oligosaccharides could be assigned the monosaccharide composition Man_2–4[Fuc]GlcNAc₂ and Man₂GlcNAc₂. These are believed to be dimannose, trimannose, and tetramannose chitobiose core oligosaccharides, three of which are fucosylated.     

Cationic Polymerization of Cyclic Sulfides

Abstract

The mechanism of the cationic polymerization of several thietanes and of propylene sulfide under the influence of triethyloxonium tetrafluoroborate in methylene chloride is described. The thietane polymerizations stop at limited conversions because of a termination reaction occurring between the reactive chain ends (cyclic sulfonium salts) and the sulfur atoms of the polymer chain. The maximum conversions obtained under identical conditions differ markedly for the different monomers. Ratios of rate constants of propagation (k_p) to rate constants of termination (k_t) have been calculated. The differences in k _p/k_t. values for the different monomers are explained in terms of differences in basicity and differences in steric hindrance of the monomers compared to the corresponding polymers. In the case of propylene sulfide it is proposed that the main termination reaction is the formation of 12-membered ring sulfonium salts by an intramolecular reaction of the third sulfur of the growing polymer chain with the reactive chain end (three-membered ring sulfonium salt). This terminated polymer is able to reinitiate the polymerization, for example, by reaction of a monomer molecule at the exocyclic carbon atom of the sulfonium salt function. The cyclic tetramer of propylene sulfide is formed in this reaction. After complete polymerization, formation of cyclic tetramer continues, probably via a backbiting mechanism. In methylene chloride as solvent, the absolute value of the rate constant of propagation for 3,3-dimethylthietane changes with changing concentration of initiator and by adding different amounts of indifferent electrolyte to the reaction mixture. From these changes, and assuming that the value of the dissociation constant of the growing chain-ends is close to values of dissociation constants of low molecular weight sulfonium salts, separate rate constants for propagation via free ions and ion-pairs were calculated. The propagation constant of free ions is about 70 times higher than that of ion pairs in methylene chloride at 20°C. Free ions and ion pairs are nearly equally reactive in nitrobenzene.     

On the Beckmann rearrangement of ketoximes: A kinetic study in trifluoromethanesulfonic acid

The formation and the destruction of an intermediate involved in the Beckmann rearrangement of 2,4,6‐trimethylacetophenone oxime have been studied in concentrated trifluoromethanesulfonic acid by kinetic and spectroscopic measurements. Observed (k_obs) and thermodynamic rate constants (k^o) have been estimated and the values compared with the ones obtained in perchloric, sulfuric, and methanesulfonic acids. In the range 80–100 wt% of sulfuric acid, combined analysis of k_obs and k^o rates shows a specific catalysis due to [H₂SO₄] species. In trifluoromethanesulfonic acid, lower rate constants, compared to the values in sulfuric acid, have been observed which differ at 99 wt% by a factor of 10³ ca. The catalytic effect of different strong acids, the structure of the intermediate inferred from Raman and NMR spectra, and the role of the ion‐pairs involved in the reaction are discussed. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 417–426, 2004     

Aquation of (N,Ndimethylformamide) pentaamminecobalt (III) perchlorate in aqueous perchlorate media

The first-order rate constants for aquation of Co(NH₃)₅(DMF)³⁺ were determined in aqueous perchlorate media. The rate constants were independent of hydrogen ion concentration and ionic strength, but decreased with increasing perchlorate ion concentration. Proton magnetic resonance studies showed that dimethylformamide was not hydrolyzed to formic acid and dimethylamine in the aquation step. Mass-spectrometer studies showed that cobalt–oxygen bond breaking occurred in 98 percent, or more, of the aquation acts. Enthalpies and entropies of activation were determined. It was concluded that aquation occurred by an I_d mechanism.     

Polymerization of acrylonitrile initiated by ceric ion–citric acid redox system

Heterogeneous polymerization of acrylonitrile initiated by ceric ammonium sulfate–citric acid (C.A.) redox system is reported at 35 ± 0.2°C under nitrogen atmosphere. The rate of monomer disappearance is found to be proportional to [C.A.]⁰, [Ce⁴⁺]^0.63, and [Monomer]^1.59. The rate of ceric ion disappearance is directly proportional to ceric ion concentration but independent of monomer concentration. The initial rate was independent of [H₂SO₄]. The molecular weight of polyacrylonitrile increases with increasing monomer concentration and decreasing ceric ion concentration. Activation energy was found to be 27.9 kJ/mol.     

苄基磺酸接枝MCM-41介孔分子筛的合成与表征

在采用溶胶-凝胶法合成纯硅MCM-41基础上，经过两步后合成处理，在纯硅MCM-41上接枝苄基磺酸，并通过X射线衍射、低温氮气吸附、红外光谱、元素分析、热重分析和酸度滴定，对所得样品进行了表征。结果表明，经过苯甲醇、氯磺酸两步接枝处理，苄基及磺酸成功地接入MCM-41上，并保持MCM-41的介孔结构，接枝后的磺酸型MCM-41比表面积和孔容均减小，分别为 976 m²·g^-1和0.42 cm³·g^-1，酸量为4.2 mmol·g^-1。     

Hydrolysis of oligosaccharides by polyelectrolytes

The hydrolysis of maltotriose, maltose, cellobiose and gentiobiose, at a concentration of 1% (w/v), have been investigated in 0.20 N sulphuric acid and 0.2 N polystyrene sulphonic acid. The apparent rate constants determined by high pressure liquid chromatography are compared and their dependence on temperature is given. The thermodynamic parameters of reaction with both acids are deduced. The catalytic effect of the polyacid, expressed by the ratio of the rate constants at a given temperature, is discussed in terms of the condensation of the counterions.     

Tin in the world of today

An ion exchanger on the basis of cellulose containing 1,2-dihydroxybenzene-3,5-disulphonic acid (Tiron) as a functional group was synthesized applying the principle of the reactive dye stuffs “Remazol” (TM of Hoechst AG). The capacity was 0.2 mmol/g, the exchange equilibrium with Fe³⁺-ions was reached within 3 min. The distribution coefficients K _d for Cu²⁺, Hg²⁺, Fe³⁺ and the alcaline earth ions were determined for the region pH 0–3. Tiron contains two kinds of functional groups, phenolic groups in orthoposition and sulphonic acid groups in meta-position. Fe³⁺ ions are bound relatively strongly by chelate formation, whereas alkaline earth ions are bound only by the sulphonic acid groups, in the sequence Ba²⁺ > Ca²⁺ > Sr²⁺ > Mg²⁺.     

Preparation and characterization of polysiloxane-poly(butyl acrylate-styrene) composite latices and their film properties

Gamma ray induced seeded emulsion co-polymerization of styrene and butyl acrylate was carried out in the presence of polymerizable polysiloxane seed latex which was obtained by the ring opening co-polymerization of octamethyl cyclotetrasiloxane (D₄) and tetramethyl tetravinyl cyclotetrasiloxane (VD₄) catalyzed by dodecylbenzene sulphonic acid (DBSA). A series of polysiloxane seed latices with different molecular weight, vinyl content, and particle size were used. The conversion-time curve showed that the polymerization rate was accelerated much by the seed latex. The obtained composite latices also showed good storage stability, mechanical stability and high electrolyte resistance ability. The morphology of the composite latex particles was found to be a quite uniform fine structure by transmission electron microscope (TEM). The graft polymerization between polymerizable polysiloxane and butyl acrylate or styrene was confirmed by the Fourier transform infrared spectroscopy (FT-IR) and the graft efficiency was also studied. The influence of seed content, molecular weight, vinyl content of the polysiloxane and seed latex particles size to the mechanical performance, water absorption ratio, surface properties, transparency and UV resistance of the latex films, was also investigated.     

Thermodynamic aspects of the Ru(III)—EDTA—ascorbate—molecular oxygen system for the oxidation of saturated and unsaturated organic compounds

The activation and thermodynamic parameters corresponding to rate and equilibrium constants, respectively, for the homogeneous oxidation of the saturated substrates, cyclohexane to cyclohexanol, cyclohexanol to cis-1,3-cyclohexane diol and olefin, cyclohexene to epoxide by Ru(III)—EDTA—ascorbateO₂ system were determined by measuring the various rates and equilibrium constants at four different temperatures in the range 288–313 K and μ = 0.1 M KNO₃ in a 50% (V/V) mixture of 1,4-dioxane and water in acidic medium. The kinetics of the oxidation of these substrates at each particular temperature was studied as a function of the concentration, the substrates, hydrogen ion, catalyst, ascorbic acid and molecular oxygen. The orders of the reaction in cyclohexanol and cyclohexene concentrations are one, and those in cyclohexane and hydrogen ion concentration are fractional and inverse first-order, respectively. For all substrates the reaction is first order with respect to the concentrations of molecular oxygen, ascorbic acid and catalyst. The source of the oxygen atom transferred to the substrates was confirmed by ¹⁸O₂ isotope studies in which the ¹⁸O was incorporated in the oxidized products. The kinetics and solvent isotope effect were studied for the oxidation of C₆H₁₂, C₆D₁₂, C₆H₁₁OH and C₆D₁₁OD. The order of the reactivity observed in the oxidation of the substrates studied is cyclohexene > cyclohexanol > cyclohexane. A comparison of the rates of oxidation of the substrates and the corresponding activation parameters with the catalytic systems Ru(III)—EDTAO₂ and Ru(III)—EDTA—ascorbateH₂O₂ indicated that activation parameters become more favourable in the presence of ascorbic acid, where the system acts as a mono-oxygenase and the activation energies are drastically reduced. Highly negative entropies are associated with all oxygen atom transfer reactions, indicating that the oxidation process is associative in nature.