The use of sulfamic acid as a primary standard in nonaqueous titrimetry

A method has been developed for the standardization of a typical nonaqueous base lithium methoxide, with an inorganic primary standard, sulfamic acid. 'T'his acid was found to dissolve readily in four independant basic solvents, dimethyl formamide, ethylenediamine, n-butylamine and dimethyl sulfoxide. Sulfamic acid could be titrated in each of these solvents, by both visual and potentiometric means with lithium methoxide dissolved in benzene-methanol. No gels nor precipitates resulted in the course of the titrations and the accuracy of the method was comparable to that obtained using benzoic acid as the primary standard. Conductometric titrations were also performed using sulfamic acid dissolved in two systems, dimethyl formamide and glacial acetic acid. In the latter solvent it was possible to titrate sulfamic acid with perchloric acid in glacial acetic acid.     

甲壳素乙酰化反应的研究

有关甲壳素的乙酰化已有报导^[1-3],但报导的各种方法在产品性能等方面尚存在不少问题。本文报导在对甲苯磺酸或高氯酸-对甲苯磺酸催化下进行甲壳素乙酰化的新方法;同时,对用单一高氯酸催化的反应作了进一步研究,从而制得了高取代度及较高比浓粘度的乙酰化甲壳素产物。     

S-benzylthiouronium salts of some carboxylic acids,sulfonic acids,and phenols

116 S-Benzylthiouronium suits have been prepared and were, if possible, checked by titration with perchloric acid in glacial acetic acid on a semi-micro scale. Out of these, 110 are salts of carboxylic acids, 2 of snlfonic acids, and 4 of nitrophenols. The melting points determined according to a standard procedure are given.     

A polymeric sulfur nitride, (sn)x,electrode responsive to ph and its application to the aqueous potentiometric titration of weak acids

The characteristics of polymeric sulfur nitride, (SN)_x, electrodes for the sensing of pH in aqueous acid—base systems is reported. The application of this new pH-sensor to titrations of both strong and weak acids with strong base is described. The (SN)_x. electrode has significant advantages for titrations of weak acids (pK_a ? 9) with a strong base, compared to the classical procedure with the glass electrode. Comparative titration curves and quantitative results for hydrochloric acid, perchloric acid, trifluoroacetic acid, boric acid, p-nitrophenol, resorcinol, glycine, phenol, acetic acid, benzoic acid and propanoic acid with glass electrode and (SN)_x electrode are given.     

Differential electrolytic potentiometric determination of some amino acids in dosage forms

The application of direct-current differential electrolytic potentiometry to the nonaqueous titration of amino acids was investigated. The basic character of amino acids in acetic acid was enhanced to permit their direct titration with perchloric acid. A pair of antimony electrodes was used as an indicating system. The shapes of the titration curves obtained were almost symmetrical with sharp peaks. The optimum current density for those titrations was found to be 1-2 microA/cm2. The procedure was applied successfully to the determination of certain amino acids in drug formulations, and the results were favorably compared statistically with those obtained by official methods.     

Trifluoromethyl sulphonic acid as a titrant in glacial acetic acid systems

Trifluoromethyl sulphonic acid in glacial acetic acid has been compared with perchloric acid in glacial acetic acid as a titrant in a limited number of cases. It does not appear that the reagent is likely to compete seriously with perchloric acid in non-aqueous titrimetry. Although comparable to perchloric acid in acid strength in acetic acid as well as in instrument response, it is unlikely that the considerably higher cost can be justified on the grounds of freedom from precipitate formation alone and no other advantageous feature has been observed which could justify this.

Abstract

Trifluoromethylsulfonsäure in Eisessig wurde mit Perchlorsäure in Eisessig als Titrationsmittel verglichen. Es scheint nicht wahrscheinlich, dass das Reagens ernsthaft mit Perchlorsäure als Titrationmittel in nichtwässrigem Medium konkurrieren kann. Das Reagens ist zwar mit Perchlorsäure vergleichbar, soweit es die Stärke (in Essigsäure) und das Ansprechen des Instrumentes betrifft; es ist aber unwahrscheinlich, dass sich die beträchtlich höheren Kosten lediglich wegen Nichtauftretens von Niederschlägen rechtfertigen lassen. Dies ist der einzige auffindbare Vorteil.     

FIA titrations of phenothiazine derivatives in aqueous micellar and non-aqueous media

New methods of flow injection analysis (FIA) neutralization titrations of phenothiazine derivatives in aqueous micellar medium of a cationic surfactant using potentiometric and spectrophotometric detection were proposed; titrations with a mixing gradient chamber and high-speed titrations were compared. The FIA titration method in non-aqueous media based on an official method of determination (titration with perchloric acid in anhydrous acetic acid) was also developed. Under optimized reaction conditions and flow-through parameters, the calibration range and equations, the sensitivity, and the repeatability of all methods were found and discussed. All titrations were assayed for medicinal forms.     

A new strategy for the synthesis of taurine derivatives using the 'safety-catch' principle for the protection of sulfonic acids

The safety-catch principle has been applied for the development of a new method for protecting sulfonic acids. 2,2-Dimethylsuccinic acid was reduced to 2,2-dimethylbutane-1,4-diol, which was selectively silylated to give 4-(tert-butyldiphenylsilanyloxy)-2,2-dimethylbutan-1-ol. Reaction of the latter compound with 2-chloroethanesulfonyl chloride in the presence of triethylamine afforded 4-(tert-butyldiphenylsilyloxy)-2,2-dimethylbutyl ethenesulfonate directly. The ethenesulfonate underwent Michael-type addition with secondary amines to give protected derivatives of taurine (2-aminoethanesulfonic acid). Deprotection was achieved on treatment with tetrabutylammonium fluoride, whereby cleavage of the silicon-oxygen bond led to an intermediate alkoxide that immediately cyclised to 2,2-dimethyltetrahydrofuran with liberation of a sulfonate. Pure sulfonic acids were obtained from the crude product by ion exchange chromatography on a strongly basic resin, which was eluted with aqueous acetic acid. The method developed should be generally applicable to the protection of sulfonic acids and is amenable to a multiparallel format.     

高取代度淀粉醋酸酯的制备

改善淀粉热塑性的方法主要是用塑化剂对其进行处理和用化学方法制备淀粉衍生物,使羟基被长链取代,减弱淀粉分子间的氢键,大分子可在较低温度下运动,从而达到降低熔融温度的目的。近年来,对高取代度淀粉醋酸酯已有报道^[1-5],Sagar等^[2]认为,粉酯的取代度越高,侧链越长,热塑性和亲水性的改变就越明显,而且酯基可起到内增塑作用,可塑性的提高反映在材料的流变学,热学及力学性能的改变上,Maheras等^[3]用高取代度的淀粉醋酸酯和纤维素醋酸酯共混,制成了纤维和塑料制品,由于高取代度淀粉醋酸酯熔点较高,Brochers等^[4]提出通过加入分子量为100－1000的增塑剂,如甘油三醋酯等,可使熔融温度降到150℃左右,Tanaka等^[6]将淀粉和乙烯类化合物在酯化催化剂的作用下反应,得到的淀粉酯性能较为理想,分子量高,具有相当好的机械性能和耐水性,国外专利报道了以甲磺酸（MSA）为催化剂制备淀粉醋酸酯的方法^[7},但对其结构和性能尚未作系统的研究,本文以冰醋酸和醋酸酐为混合酸,MSA为催化剂,制得了具有较高取代度的高直链淀粉醋酸酯,并系统研究了反应温度,反应时间,反应物比例等不同反应条件对取代度的影响,通过红外分析,特性粘度测试,溶解性等分析手段,表征了高直链淀粉醋酸酯的结构与性能。     

The assay of sodium citrate and sodium potassium tartrate by cation exchange and non-aqueous titrimetry

Sodium citrate and sodium potassium tartrate are assayed by passing aqueous solutions of the salts through cation exchange resin columns, concentrating the effluents from the columns, and then titrating the effluents with standard sodium hydroxide solution. Sodium citrate is assayed by titrating a solution of the salt in glacial acetic acid with standard acetous perchloric acid, the end-point being detected potentiometrically; sodium potassium tartrate is assayed by stirring the salt in excess standard acetous perchloric acid, and then backtitrating the excess acetous perchloric acid with standard acetous potassium acetate, the end-point being detected potentiometrically.     

Investigation of naphthyridines. 16. Synthesis of derivatives of 2,5-dioxo-1,2,5,6,7,8-hexahydro-1,6-naphthyridine-3-carboxylic acids from anilides (hydrazides) of 6-oxo-2-styrylnicotinic acids

Heating anilides (hydrazides) of 5-cyano-6-oxo-2-styrylnicotinic acids in polyphosphoric acid (PPA) leads to amides of 7-aryl-2,5-dioxo-6-phenyl(amino)-1,2,5,6,7,8-hexahydro-1,6-naphthyridine-3-carboxylic acids, which on heating with perchloric acid in acetic acid give the corresponding acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1809–1812, December, 2004.For Part 15 see [1].     

Biamperometric end-point detection with quinhydrone electrodes in coulometric neutralization titrations in nonaqueous media

Some new possibilities for continuous coulometric titration of bases, alone and in mixture, as well as of mineral acids, alone and in mixture, were investigated with acetic anhydride-anhydrous acetic acid as solvents. The titration end point was determined biamperometrically. It was established that quinhydrone electrodes with platinum, palladium, and gold as the metal phase can be equally satisfactorily applied to the end-point determination of both the titrations of bases or acids alone, and of their two-component mixtures. Amounts of 6–10 μequiv. of bases, i.e., 20–47 μequiv. of mineral acids, were determined with the maximal average deviation of 1.4%. Results of biamperometric determinations of bases are compared to those of catalytic thermometric determinations, while those of acids are compared with the results of photometric titrations. The agreement between the methods is satisfactory.     

Catalytic Thermometric Titrations of Various Mixtures of Nitrogen Bases

The reactions of acetylation of hydroquinone and quinhydrone with acetic anhydride, catalysed by perchloric acid, were used to determine the end point of catalytic thermometric titrations of a number of different amines and amides dissolved either in acetic anhydride or in acetic acid-acetic anhydride (10+1) mixture. In the majority of cases primary and secondary amines could be successfully determined if pKb_b≤9.3, tertiary amines if pK_b≤14, and amides if pK_b≤l5. Thanks to the difference in behaviour of organic bases in acety lation reaction, it was possible in some instances to determine selectively the individual bases in their mixtures. Catalytic titrations appeared to be especially suitable for the determination of extremely weak bases, even in the case of using mixtures of organic solvents, when Potentiometrie titrations could not be employed. Amounts of 2.5·10^?6-8·10^?5 mole of bases were determined with a maximal relative standard deviation less then 2%.     

Electrochemical studies of sulfonates in non-aqueous solvents: Part III. Trifluoromethanesulfonic acid as a strong acid in dipolar aprotic solvents and acetic acid

Dissociation of trifluoromethanesulfonic acid in non-aqueous solvents has been investigated mainly by conductometry and compared with that of p-toluenesulfonic, methanesulfonic, fluorosulfuric and perchloric acids. The solvents used are dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, n-butyronitrile, propylene carbonate, acetonitrile, nitromethane, methyl isobutyl ketone and acetic acid. Trifluoromethanesulfonic acid is completely dissociated in rather basic solvents such as dimethyl sulfoxide, dimethylacetamide and dimethylformamide, while it is associated to some extent in the other solvents, especially in methyl isobutyl ketone and acetic acid. The strength of trifluoromethanesulfonic acid is almost the same as that of perchloric acid in all the solvents. Dissociation constants of the other acids are also obtained.     

Biamperometric neutralisation titrations in non-aqueous solvents applying tin electrode pair for the end-point detection

Summary Tertiary amines and salts of organic acids in acetic anhydride with 5% of acetic acid were titrated applying a biamperometric indicating system consisting of a polarised or unpolarised pair of tin electrodes by means of 0.1 N perchloric acid in glacial acetic acid. Amounts of 15.4–29.8 mg were analysed with average deviations of <0.6%, the results obtained being in a good agreement with those of potentiometry. The biamperometric end-point detection using an indicating system of polarised pair of tin electrodes can be applied for coulometric determinations of these bases with satisfying accuracy. By means of anodic generation of hydrogen ions in the presence of hydroquinone amounts of 0.5–1.0 mg were titrated with average deviations of < 1.3%. The results obtained were compared with those obtained of catalytic thermometric and photometric titrations.

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Biamperometrische Neutralisationstitrationen in nichtwärigen Lösungsmitteln unter Anwendung eines Zinn-Elektrodenpaares als Indicatorsystem

Zusammenfassung Tertiäre Amine und Salze organischer Säuren werden in Acetanhydrid mit 5% Essigsäure durch Titration mit einer 0,1 N Lösung von Perchlorsäure in Essigsäure bestimmt. Das verwendete biamperometrische Indicatorsystem besteht aus einem Paar polarisierter oder nichtpolarisierter Zinnelektroden. Mengen von 15,4–29,8 mg wurden mit einer mittleren Abweichung von <0,6% analysiert. Die Ergebnisse stimmen gut mit denen von potentiometrischen Titrationen überein. Die biamperometrische Endpunkttechnik mit polarisierten Zinnelektroden kann für coulometrische Bestimmungen dieser Basen mit zufriedenstellender Genauigkeit benutzt werden. Durch anodische Erzeugung von Wasserstoffionen in Gegenwart von Hydrochinon wurden Mengen von 0,5–1,0 mg mit einer mittleren Abweichung von < 1,3% titriert. Die Ergebnisse wurden mit denen von katalytisch-thermometrischen und photometrischen Titrationen verglichen.

     

Dichloramine-T as a new oxidimetric titrant in non-aqueous and partially aqueous media

A new oxidimetric titrant, dichloramine-T, is proposed for redox titrations in glacial acetic acid medium. The general analytical conditions for using this oxidant and the procedures for potentiometric determination of ascorbic acid, iodide, arsenic(III) and iron(II) are described.     

Fluorescence study of toluic and anisic acid isomers

The fluorescence of benzoic acid and some of its derivatives (including toluic and anisic acids isomers) in 10% glacial acetic acid-chloroform as a solvent is presented. The percentage of glacial acetic acid that maximizes the fluorescence of these isomers is between 5 and 10%. The excitation and the emission wavelengths of all isomers are presented in addition to limits of detection, relative standard deviations, and fluorescence band half-widths. The stabilities of these isomers are studied and the determination of one isomer in the presence of other isomers is reported.     

Oxidation of organic substances with compounds of trivalent manganese: XIII. Oxidation of pyruvic acid with manganese(III) sulfate in a medium of sulfuric acid and with hexaquomanganese(III) ions in noncomplexing medium of perchloric acid

The oxidation of pyruvic acid with manganese(III) sulfate in a medium of sulfuric acid and with hexaquomanganese(III) ions in noncomplexing perchloric acid medium was studied. It was found that pyruvic acid is oxidized by both reagents to give acetic acid and carbon dioxide and the optimal conditions for the analytical application of this reaction on both a semimicro and micro level were found.     

The conductometric titration of carboxylic and phenolic acids in non-aqueous solutions: The resolution of acid mixtures and some practical applications

A detailed study has been made of non-aqueous conductometric titrations suitable for the resolution of acid mixtures. The optimum conditions for the various determinations with respect to base and solvent are extensively discussed. The applications include determinations of diphen-ylolpropane, naphthenic acids, perchloric acid and mixtures containing sulphuric acid.     

A re-evaluation of hydroxylammonium acetate as a carbonyl reagent — the effect of dielectric constant change on titration end-points

The determination of carbonyl groups with hydroxylammonium acetate in acetic acid has been re-examined. The reaction of hydroxylammonium acetate with acetic acid has been found to yield non-basic products, first acethydroxamic acid and eventually diacetylhydroxylamine, which do not interfere with the analyses. Calculations based on kinetics show that loss of the reagent is negligible in most cases, and in the extreme, involves only 0.9% of the amount originally present. Analyses in acetic acid media throughout are compared with those in which the titrations were conducted in benzene-acetic acid or carbon tetrachloride-acetic acid mixtures whose compositions were chosen to yield the most favorable titrations. The slopes of the titration curves were uniformly improved in the systems containing inert solvents, as predicted by consideration of the effect of dielectric constant change. Analytical precision was slightly improved except for aromatic aldehydes. Neither inert solvent system seemed superior to the other. The undesirable effect of small amounts of water is discussed.