Acidity Constants of Supported Salts of Heteropoly Acids Using a Methodology Related to the Potentiometric Mass Titration Technique

Using a potentiometric mass titrationmethod, the pK_a values of 12-molybdophosphoric acid (MPA) and 12-tungstophosphoric acid (TPA) were determined in aqueous solution and as a solid suspension in acetonitrile. The results were compared with the earlier reported values obtained using other methods like calorimetry and adsorption (Cal-ad). The acidity values in terms of pK_a and the number of acid sites were determined for the ammonium salts of MPA and TPA, and ammonium salts incorporated with vanadium and ammonium salts impregnated on a ZrO₂ support. The effect of the amount of the salt or acid in the suspension of acetonitrile on the potentiometric titration behavior was also studied and it was found that 0.1 g of the substance gives a good neutralization jump in the titration curve.     

Adsorption of gaseous formaldehyde and carboxylic acids by ammonium-ion-exchanged alpha-zirconium phosphate

Ammonium-ion-exchanged alpha-Zr(HPO(4))(2)H(2)O (alpha-ZrP) was obtained as a single phase with the interlayer distance of 9.4 A by the ion-exchange of proton with ammonium ion. The ammonium ion-exchanged alpha-ZrP could adsorb ill-smelling gases, such as formaldehyde and carboxylic acids (formic acid, acetic acid, propionic acid, and butyric acid). The adsorption amounts of carboxylic acids increased in the order, butyric acid相似文献   

Electron-beam graft-modified membranes with externally controlled flux

Pre-irradiation grafting as a means to modify commerical poly(vinylidene fluoride) (PVDF) membranes has been studied. The membranes prepared were weak cation-exchange membranes (acrylic acid functionality), anion-exchange membranes (trimethyl ammonium functionality) and temperature-sensitive membranes (N-isopropyl amide functionality). Different graft loads were obtained by varying reaction time, radiation dose and in the case of acrylic acid the graft solution composition. The trimethyl ammonium chloride functionality was obtained by grafting vinyl benzyl chloride onto a PVDF membrane and aminating the benzyl chloride groups in a 45% trimethyl amine–water solution. For a membrane grafted with 9 wt% acrylic acid the flux increased approximately 70 times when the pH was decreased from 6 to 2. For a membrane with 5 wt% trimethyl ammonium functionality the flux increased both when pH was decreased below 3 and increased above 11. For a membrane grafted with 18 wt% N-isopropyl acrylamide a sharp increase of flux was observed when the temperature was raised above 32°C.     

Method of separating uranium from iron and thorium

Acid leaching of uranium deposits is not a selective process. Sulfuric acid solubilizes iron(III) and half or more of the thorium depending on the mineralog of this element. In uranium recovery by solvent extraction process, uranium is separated from iron by an organic phase consisting of 10 vol% tributylphosphate(TBP) in kerosine diluent. Provided that the aqueous phase is saturated with ammonium nitrate or made 4–5 M in nitric acid prior to extraction. Nitric acid or ammonium nitrate is added to the leach solution in order to obtain a uranyl nitrate product. Leach solutions containing thorium(IV) besides iron are treated in an analogous fashion. Uranium can be extracted away from thorium using 10 vol% TBP in kerosine diluent. The aqueous phase should be saturated with ammonium nitrate and the pH of the solution lowered to 0.5 with sufficient amount of sulfuric acid. In other words, the separation of uranium and thorium depends on the way the relative distributions of the two materials between aqueous solutions and TBP vary with sulfuric acid concentration. Thorium is later recovered from the waste leach liquor, after removal of sulfate ions. Uranium can be stripped from the organic phase by distilled water, and precipitated as ammonium diuranate.     

Analysis of oligodeoxynucleotides by negative-ion matrix-assisted laser desorption mass spectrometry

Thirty compounds were tested in combination with ammonium acetate for the ability to desorb and ionize oligodeoxynucleotides by ultraviolet matrix-assisted laser desorption mass spectrometry. Negative ion yields using matrices such as 2,5-dihydroxybenzoic acid and 3-hydroxy-4-methoxybenzaldehyde are enhanced by the addition of ammonium salts at a molar ratio of 1:1, pH 7. 3-Hydroxy-4-methoxybenzaldehyde was tested with 12 different ammonium, alkylammonium, and pyridinium salts for the ability to cocrystallize with oligodeoxynucleotides and to improve desorption and ionization. Ions of oligodeoxynucleotides 9, 10, and 11 nucleotides in length were observed with a matrix of 3-hydroxy-4-methoxybenzaldehyde and ammonium acetate, pH 7, at a mass resolution of 100–150 (fwhm). A small oligodeoxynucleotide (11-mer) was observed at the femtomole level with a combination of 2,5-dihydroxybenzoic acid and ammonium acetate as the matrix. Ions from single stranded DNA (60 nucleotides in length) were also observed using this same matrix combination. The results of these studies have shown that both sensitivity and desorption conditions need to be further improved before complex mixtures of large pieces of DNA can be effectively analyzed.     

Dry state preparation of radioiodine labeled meta-iodobenzylguanidine

Radioiodination of meta-iodobenzylguanidine (MIBG) by the isotopic exchange technique in the dry state has been performed. Benzoic acid, pivalic acid and acetamide have been used as molten protic media to promote isotopic exchange reactions. Ammonium sulphate, diammonium hydrogen ortho-phosphate and ammonium chloride were used as catalysts which provide acidic media to facilitate exchange reactions. Maximum radiochemical yields of 97.1±1.3% and 84.3±1.6% [¹³¹I] MIBG were obtained when ammonium sulphate and benzoic acid were used. High radiochemical yields of 88.3±1.1% and 74.4±1.5% [¹³¹I] MIBG were also obtained in case of diammonium hydrogen orthophosphate and pivalic acid which suggests their successful use as reaction media in the radioiodination of MIBG. The activation energy for the exchange reaction in ammonium sulphate was calculated to be 10.8 kcal/mole.     

Modifying attapulgite clay by ammonium citrate tribasic for the removal of radionuclide Th(IV) from aqueous solution

The ammonium citrate tribasic was successfully modified to attapulgite clay and the effect of modifying was characterized by FTIR and XRD techniques. Experimental results showed that the ammonium citrate tribasic modified attapulgite clay had a strong sorption ability to remove Th(IV) from aqueous solutions. The sorption of Th(IV) from aqueous solutions has been systematically investigated as a function of several variables including contact time, solid content, pH, ionic strength, Fulvic acid (FA)/humic acid (HA) and temperature under ambient conditions. The results indicate that the sorption of Th(IV) onto ammonium citrate tribasic modified attapulgite clay is strongly dependent on pH, Th(IV) initial concentration, ionic strength, temperature and HA/FA. Surface complexation and ionic exchange are the main sorption mechanisms. Sorption of Th(IV) onto ammonium citrate tribasic modified attapulgite is quick and can be fitted by a pseudo-second-order rate model very well. Sorption of Th(IV) onto ammonium citrate tribasic modified attapulgite is promoted at higher temperature and the sorption reaction is an endothermic process. Langmuir isotherm model fits the experimental data better than Freundlich and D-R isotherm models. The results suggest that the ammonium citrate tribasic modified attapulgite sample is a suitable material in the preconcentration and solidification of radionuclide Th(IV) from large volumes of aqueous solutions.     

Synthesis of 1,2,4,5-tetrasubstituted imidazoles using silica-bonded propylpiperazine N-sulfamic acid as a recyclable solid acid catalyst

A simple and efficient procedure for the preparation of silica-bonded propylpiperazine-N-sulfamic acid (SBPPSA) by the reaction of 3-piperazine-N-propylsilica (3-PNPS) and chlorosulfonic acid in chloroform is described. Silica-bonded propylpiperazine-N-sulfamic acid is employed as a recyclable catalyst for the synthesis of highly substituted imidazoles from the reaction of benzil, aromatic aldehydes, ammonium acetate and amines under solvent-free conditions. The heterogeneous catalyst was recycled for five runs upon the reaction of benzil, 4-methylbenzaldehyde, benzylamine, and ammonium acetate without losing its catalytic activity.     

硅胶键合的N-丙基三亚乙基四胺氨基磺酸作为可回收固体酸催化剂催化合成2-氨基-4,6-二芳基烟腈(英文)

A simple and efficient procedure for the preparation of silica-bound N-propyl triethylenetetramine sulfamic acid(SBPTETSA) by the reaction of silica-bound N-propyl triethylenetetramine(SBPTET) with chlorosulfonic acid in chloroform is described.Silica-bound N-propyl triethylenetetramine sulfamic acid was employed as a recyclable catalyst for the synthesis of 2-amino-4,6-diarylnicotinonitriles from the multi-component reaction of an acetophenone derivative,an aromatic aldehyde,malononitrile,and ammonium acetate under solvent-free conditions at 100 °C.The heterogeneous catalyst was recycled for five consecutive runs in the optimized multi-component reaction of 4-chloroacetophenone,4-chloroenzaldehyde,malononitrile,and ammonium acetate without significant loses to its catalytic activity.     

Enhanced detection of phosphopeptides in matrix-assisted laser desorption/ionization mass spectrometry using ammonium salts

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) has been used successfully to detect phosphorylation sites in proteins. Applications may be limited by the low response of phosphopeptides compared to nonphosphorylated peptides in MALDI MS. The addition of ammonium salts to the matrix/analyte solution substantially enhances the signal for phosphopeptides. In examples shown for equimolar mixtures, the phosphorylated peptide peaks become the largest peaks in the spectrum upon ammonium ion addition. This can allow for the identification of phosphopeptides in an unfractionated proteolytic digestion mixture. Sufficient numbers of protonated phosphopeptides can be generated such that they can be subjected to postsource decay analysis, in order to confirm the number of phosphate groups present. The approach works well with the common MALDI matrices such as α-cyano-4-hydroxycinnamic acid and 2,5-dihydroxybenzoic acid, and with ammonium salts such as diammonium citrate and ammonium acetate.     

Syntheses of chiral homoazacalix[4]arenes incorporating amino acid residues: molecular recognition for racemic quaternary ammonium ions

Chiral calixarene analogues incorporating amino acid residues into the macrocyclic rings were prepared from the cyclization reactions of bis(chloromethyl)phenol-formaldehyde tetramer with amino acid methyl ester in moderate yields. The macrocycles form a chiral concavity, which is induced by the chiral transmission from the point chirality of the amino acid residues to the phenol-formaldehyde tetramer unit. The macrocycles have the cavity pi-basic enough to include the quaternary ammonium ion due to the cation-pi interaction and can serve as a shift reagent for racemic ammonium ions during 1H NMR analysis.     

1-氨基乙叉1,1-二膦酸的合成及其阻垢和缓蚀性能

有机多膦酸是一类多齿配体的螯合剂,能与许多金属离子形成稳定的配合物,70年代国内合成了1-羟基乙叉1,1-二膦酸(HEDP),并已应用于水质稳定,金属缓蚀和无氰电镀。Lukevico 用甲腈、三溴化磷和醋酸合成了1-氨基乙叉1,1-二膦酸 CH_3C(NH_2)(P(O)(OH)_2]_2(AEDP)后,又有人用醋酰胺、醋酸酐、亚磷酸或醋酸铵、醋酸酐、亚磷酸以及醋酸铵、醋酰胺、三氧化二磷(P_4O_6)为原料进行了合成,本文报导用尿素、冰醋酸、三氯化磷合成 AEDP 及其阻垢和缓蚀性能.     

Phosphinoselenothioic acids and their salts: synthesis, characterization, and reaction with electrophiles

[reaction: see text] Phosphinoselenothioic acid ammonium salts were synthesized in good yields by reacting phosphinoselenothioic acid S-[2-(trimethylsilyl)ethyl] esters with ammonium fluorides. Phosphinoselenothioic acid alkali metal salts were obtained as 18-crown-6 ether complexes with high efficiency by treating the esters with alkali metal fluorides and 18-crown-6 ether. The salts were stable under air and soluble in water. The structures of the phosphinoselenothioic acid tetramethylammonium salt and P-methylseleno-P-methylthiophosphonium triflate were determined by X-ray molecular structure analyses. These salts exhibited monomeric structures, and the central phosphorus atoms adopted tetrahedral structures. Alkylation of the ammonium salts selectively gave phosphinoselenothioic acid Se-alkyl esters, whereas acylation of the salts preferentially gave S-acyl products. Protonation of the salts selectively gave the phosphinoselenothioic S-acid. The S-acid generated in situ was reacted with alpha,beta-unsaturated carbonyl compounds and cyclohexene oxide to give the adducts. Molecular orbital calculations were carried out for the model compound H2P(Se)S- to elucidate the electronic structure.     

Ammonium eneselenolates: stereochemistry and electronic properties.

Ammonium eneselenolates were generated with high efficiency by reacting selenothioic acid S-esters with a THF solution of TBAF. The methylation of ammonium eneselenolates gave ketene selenothioacetals as stereoisomeric mixtures. The ratio of the two stereoisomers depended on the duration of the reaction before the addition of MeI. Ammonium eneselenolates were characterized by examining their (1)H, (13)C, and (77)Se NMR spectra, which indicated that ammonium eneselenolates were present almost exclusively as Z-isomers. These results suggested that ammonium eneselenolates are kinetically generated as stereoisomeric mixtures, and isomerization of E-isomers to Z-isomers then takes place to result in the exclusive formation of Z-isomers. During the methylation of Z-isomers of ammonium eneselenolates, the isomerization of Z-isomers to E-isomers occurs to give stereoisomeric mixtures of ketene selenothioacetals. NMR spectra of ammonium eneselenolates implied that the electrons at the selenium atom are somewhat delocalized to the carbon-carbon double bond and the carbon-selenium bond shows partial double-bond character.     

The first ammonium aromatic diselenoates: stable heavy congeners of aromatic carboxylic acid salts

Ammonium aromatic diselenoates were synthesized by reacting aromatic diselenoic acid 2-(trimethylsilyl)ethyl esters derived from aluminum 2-(trimethylsilyl)ethyl selenolate with aromatic selenoic acid O-methyl esters with ammonium fluorides. The results of molecular structure analysis and NMR studies of ammonium salts supported the double-bond character between the carbon atom and selenium atoms.     

Struvite precipitation for ammonia nitrogen removal in 7-aminocephalosporanic acid wastewater

7-Aminocephalosporanic acid wastewater usually contains high concentrations of ammonium (NH??-N), which is known to inhibit nitrification during biological treatment processes. Chemical precipitation is a useful technology to remove ammonium from wastewater. In this paper, the removal of ammonium from 7-aminocephalosporanic acid wastewater was studied. The optimum pH, molar ratio, and various chemical compositions of magnesium ammonium phosphate (MAP) precipitation were investigated. The results indicated that ammonium in 7-aminocephalosporanic acid wastewater could be removed at an optimum pH of 9. The Mg2?:NH??-N:PO? 3?-P molar ratio was readily controlled at a ratio of 1:1:1.1 to both effectively remove ammonium and avoid creating a higher concentration of PO? 3?-P in the effluent. MgCl?·6H?O + 85% H?PO? was the most efficient combination for NH??-N removal. Furthermore, the lowest concentration of the residual PO? 3?-P was obtained with the same combination. Struvite precipitation could be considered an effective technology for the NH??-N removal from the 7-aminocephalosporanic acid wastewater.     

Swelling studies of copolymeric acrylamide/crotonic acid hydrogels as carriers for agricultural uses

In this study, highly swollen acrylamide/crotonic acid hydrogels (in a rod form) containing some inorganic salts such as ammonium nitrate, potassium nitrate and ammonium sulphate used as fertilizer, an agricultural drug such as Dalapon (sodium 2,2‐dichloropropionate) and two crosslinkers such as ethylene glycol dimethacrylate and 1,4‐butandiol dimethacrylate were prepared by copolymerization of acrylamide and crotonic acid with γ‐radiation. As a result of swelling tests, the influence of γ‐ray dose and relative content of crotonic acid on the swelling properties, the diffusional behavior of water, diffusion coefficients and network properties of the hydrogel systems were examined. Acrylamide/crotonic acid hydrogels containing these salts and agricultural drug were swollen in the range 2045–400% in water, while polyacrylamide hydrogels swelled in the range 660–700%. Water intake of hydrogels followed a nonFickian‐type diffusion. Copyright © 2000 John Wiley & Sons, Ltd.     

Titanium(IV) chloride and quaternary ammonium salt promoted Baylis-Hillman reaction.

The Baylis-Hillman reaction of aldehydes with alpha,beta-unsaturated ketones can be drastically affected by the reaction temperature and Lewis bases. When the reaction was carried out at -78 degrees C using catalytic amounts of quaternary ammonium salts (R4N+X-, X = Cl, Br, I) as Lewis bases, in the presence of titanium(IV) chloride, the chlorinated aldol adduct 1 was obtained as the major product. Quaternary ammonium bromides and iodides (R4N+X-, X = Br, I) have higher catalytic activity than corresponding chlorides (R4N+Cl-). Quaternary ammonium fluorides (R4N+F-) do not have activity at all. The amounts of Lewis acid and quaternary ammonium salts used affect the reaction rate and product. A plausible reaction mechanism is proposed. If the reaction was carried out at room temperature (about 20 degrees C) in the presence of titanium(IV) chloride and quaternary ammonium salts (R4N+X-, X = Cl, Br, I), the elimination product 3, derived from 1, was formed as the major product.     

Synthese et etude de celluloses echangeuses d'ions. Leur emploi dans l'epuration des eaux residuaires de l'industrie textile—1: Synthese d'une cellulose greffee par des chaines poly (acide acrylique) et d'une cellulose renfermant des fonctions ammonium quaternaire

For use as ion exchangers and particularly as purification agents for textile industrial effluents, cellulose grafted with polyacrylic acid and cellulose substituted by quaternary ammonium functions have been prepared. For both syntheses, the influences of experimental parameters have been studied in detail and the optimum conditions for large-scale preparation have been determined. Large amounts of modified cellulose have been obtained and tested in industry (cf. part III). The grafting by acrylic acid has been carried out by the ceric-ion method; the quaternary ammonium cellulose has been obtained by condensation of cellulose with epoxy propyl triethyl ammonium chloride. Synthesis of this salt in the presence of cellulose has been achieved so that the quaternary ammonium cellulose can be obtained from cellulose and epichlorhydrin in one step.     

Novel Method of Synthesis of Quaternary Ammonium Tribromides and Investigation of Catalytic Role of Benzyltrimethylammonium Tribromide in Oxidation of Alcohols to Carbonyl Compounds

Stable crystalline organic quaternary ammonium tribromides (QATBs) have been easily synthesized by the oxidation of the corresponding organic ammonium bromides (QABs) with ammonium persulfate. The reactions have been performed under solvent-free conditions in the presence of sulfuric acid and silica as supporting agent. Two equivalents of potassium bromide have been used as the source of additional bromides for quantitative conversion of QABs to QATBs. Ammonium persulfate, a cheap and readily available oxidant, carries out the bromide oxidation to tribromide very effectively under solvent-free conditions. The synthesized QATBs have been shown to catalyze the oxidation of alcohols to carbonyl compounds with hydrogen peroxide as oxidant in good yields under mild reaction conditions.