Reactivity and catalytic activity of cationic lonomers for the nucleophilic substitution reactions

Polystyrene-based crosslinked cationic ionomers containing ammonium or phosphonium chlorides (AxRCI and PxBuCI) were reacted with decyl methanesulfonate. The kinetic data were correlated with the swelling behavior of the ionomers and the solution viscosity of the corresponding linear ionomers. The reactivity of the ionomers was independent of the particle size of the ionomer beads, indicating no diffusion control of the reaction. The solvent and the ion content of the ionomers greatly affect the reactivity. In nonpolar solvents with a low acceptor number, A_N, such as toluene, the aggregation of ionic groups with an increasing ion content reduces the reactivity. A solvent with a high value of A_N, such as chloroform, led a very low reactivity independent of the ion content. Aprotic polar solvent, such as acetonitrila, promoted the dissociation of the ionic groups and furnished a relatively high reactivity independent of the ion content. Several catalytic substitution reactions were carried out under liquid-solid-solid triphase conditions. The kinetic results were accounted for in terms of slow nucleophile transport and fast chemical reaction within the ionomer particles. © 1994 John Wiley & Sons, Inc.     

Spectrophotometric resolution of ternary mixtures of pseudoephedrine hydrochloride, dextromethorphan hydrobromide, and sodium benzoate in syrups using wavelength selection by net analyte signals calculated with hybrid linear analysis

Hybrid linear analysis (HLA), as a recent factor-based multivariate calibration technique, was applied for the spectrophotometric determination of ternary mixtures of pseudoephedrine hydrochloride (PSU), dextromethorphan hydrobromide (DXT), and sodium benzoate (BNZ). The utilized HLA was assisted by a wavelength selection procedure which was based on the calculation of the net analyte signal (NAS) regression plot in any considered wavelengths window for each test sample, in addition to a moving window strategy for searching the region with maximum linearity of NAS regression plot (minimum error indicator (EI)). HLA was applied because it was simpler to adapt to the NAS regression plot methodology, and also used less factors than partial least squares (PLS). An orthogonal array design was applied for formation of calibration and prediction sets in the concentration ranges 0-7500 μmol L⁻¹ for PSU, 0-300 μmol L⁻¹ for DXT, and 0-1400 μmol L⁻¹ for BNZ. The method had the ability to select wavelength regions that minimize the effect of non-linearity of the spectral data, in addition to that of non-modeled interferences. The application of the selected wavelength regions improved the obtained relative standard error of predictions for PSU, DXT, and BNZ, respectively, from 5.24, 8.67, and 5.48% to 2.19, 5.21, and 3.62% (using lower number of factors). To check the ability of the proposed method in selection of linear regions of spectra, a test for detecting non-linear regions of spectral data in multivariate spectroscopic assays was also described. Additives in the commercial syrup samples did not interfere with their determinations. The method was successfully applied for the determination of pseudoephedrine HCl, dextromethorphan HBr, and sodium benzoate in cough suppressant syrup samples.     

Facile conversion of amides and lactams to selenoamides and selenolactams using tetraethylammonium tetraselenotungstate

Chloroiminium salts generated in situ from amides and lactams using (COCl)₂ or POCl₃ react very readily with the new selenium transfer reagent, tetraethylammonium tetraselenotungstate, (Et₄N)₂WSe₄, 1, to afford the corresponding selenoamides and selenolactams in excellent yields under mild reaction conditions.     

Condensed tetrazolo-1,3,5-triazines. 4. Synthesis of salts of 5-aminotetrazolo[1,5-a]-1,3,5-triazin-7-one

2-Amino-4-azido-1,3,5-triazin-6(1H)-ones were synthesized by successive substitution of the trinitromethyl groups in 2-amino-4,6-bis(trinitromethyl)-1,3,5-triazines under the influence of azide and nitrite ions. Interaction of 2-amino-4-azido-1,3,5-triazin-6(1H)-ones with bases led to the azido-tetrazole tautomeric conversion give salts of 5-aminotetrazolo[1,5-a]-1,3,5-triazin-7-one. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1211–1219, August, 2006.     

HPLC post column derivatization of aromatic amines usingN-methyl-9-chloroacridinium triflate

An HPLC post column chemical derivatization procedure based on the interaction between an acridinium triflate and amines to form highly colored derivatives on-line is described for the determination of aromatic amines. Benzocaine and butesin, local anesthetic agents that contain the aromatic amine group, were used as model compounds. Reversed-phase HPLC conditions were developed for both the separation of analytes and the reaction between analytes and the acridinium triflate in the system. Three-dimensional knitted teflon shape coils and the internal diameter and length of the coils were important parameters in reducing band broadening and background noise.N-Methyl-9-chloroacridinium triflate was shown to be applicable to the determination of primary aromatic amines, selected secondary aromatic amines, hydrazides, and hydrazines. Application of the on-line chemical derivatization procedure to the analysis of pharmaceutical dosage forms containing procainamide (primary aromatic amine), isoniazid (hydrazide), and hydralazine (hydrazine) is also described.     

Thermodynamic properties of the gaseous barium silicates BaSiO2 and BaSiO3

In the present study, the stability of gaseous barium silicates was confirmed by the high temperature mass spectrometry. On the basis of equilibrium constants measured for gas-phase reactions, the standard formation enthalpies were determined for gaseous barium silicates as (−510 ± 15) kJ · mol⁻¹ and (−884 ± 18) kJ · mol⁻¹ at 298 K; standard atomization enthalpies as (1637 ± 17) kJ · mol⁻¹ and (2318 ± 20) kJ · mol⁻¹ at 298 K for BaSiO₂ and BaSiO₃, respectively. Based on the results obtained the critical analysis of the literature data was carried out.     

Synthesis of an N-glycan decasaccharide of the hybrid type

A hybrid-type N-glycan decasaccharide GlcNAcMan₇GlcNAc₂ was synthesized from the pentasaccharide GlcNAcMan₂GlcNAc₂ as an advanced intermediate and an acyl-protected pentamannosyl donor. Benzyl mannoside was regioselectively benzoylated and glycosylated at OH-3 and OH-6 with a dimannoside to give the 3,6-branched pentamannoside. Coupling of the two pentasaccharides furnished the target decasaccharide in 60% yield. Deprotection of the base labile functions furnished a hybrid-type N-glycan decasaccharide functionalized for the conjugation with peptides or proteins.     

NMR位移试剂Eu(fod)~4^-对锍盐^1H和^1^3C NMR的影响

合成了八种新的四氟硼酸二甲基苯基锍，用元素分析和核磁共振对其结构进行了表征。研究了以CDCl~3为溶剂，NMR位移试剂Eu(fod)~4^-对所合成锍盐的^1H和^1^3C NMR的影响。结果表明，Eu(fod)~4^-是一个对锍盐非常有效的位移试剂，且Eu(fod)~4^-对二甲基苯基锍盐之甲基的^1H和^1^3C NMR的位移呈线性关系。     

Apparent molal volumes of aqueous solutions of bis-tetraalkylammonium salts at 25°C: Methylene-group contribution to the limiting molal volume

Densities of aqueous solutions of a series of polymethonium chloride and bromide salts (CH₃)₃–N–(CH₂)_n–N–(CH₃)₃X₂ have been measured at 25°C. Apparent molal volumes have been calculated, and methylene-group contributions to the limiting apparent molal volumes °_v have been estimated. Constant values of the methylene-group contribution of 16.5 and 17.0 cm³-mole^–1 were obtained for the bromide and chloride salts, respectively. These values are consistent with methylene-group contributions reported for other series of organic electrolytes.     

Activities of Individual Ions From Infinite Dilution to Saturated Solutions

A new procedure, which provides a closer approximation for the junction potentials than the Henderson equation, is tested to reduce new emf data for the chloride ion in CsCl solutions and previously measured data for individual ions in aqueous solutions of KCl, NaCl, and NaBr. The liquid junction potential is calculated from numerical integration of its basic equation without assuming constant mobility or using concentrations instead of activities. The mean ionic activity coefficients of the salts, obtained from the activity coefficients of the individual ions, show good agreement with values reported in the literature. The activity coefficients of the individual chloride ion at 25°C in aqueous solutions of CsCl up to 3 molal and in KCl solutions were measured using a chloride ion-selective electrode. It has been confirmed that the activity of the chloride ion is equal to the activity of the cation in CsCl solutions and, contrary to the prediction of hydration theory, it is higher than the activity of the cation in aqueous KCl solutions. The New Hydration Theory has been developed to overcome the shortcomings of the older hydration theory and has been used to smooth the experimental activity coefficients of the individual ions in aqueous solutions and to extrapolate them up to the saturated solution.