New reagents 41. Reduction of sulphonyl chlorides and sulphoxideswith aluminum iodide

Aluminium iodide reduces sulphonyl chlorides to disulphides and sulphoxides to sulphides under mild conditions in acetonitrile.     

Reactions of aromatic sulphonyl chlorides with anilines : Studies of solvent effects by the approach of multiparameter empirical correlations

The reaction kinetics of 5-substituted 2-thiophenesulphonyl chlorides with anilines were studied in fourteen pure solvents (protic and aprotic) and in mixed solvents at 25°. The approach of multiparameter equations to describe solvent effects according to the Palm-Koppel and Krygowski-Fawcett models was unsuccessful. Instead satisfactory single parameter linear correlations, one for protic solvents with positive slope and another for aprotic solvents with negative slope, were found by using the dielectric constant ?. An S_AN mechanism for these reactions was proposed, bond-making being the rate-determining step for protic solvents and bond-breaking for aprotic ones. The analysis of some data for the reactions of benzenesulphonyl chloride showed that the mechanism is analogous also for this substrate and the rate-determining step is depending on both solvent and nucleophile. Hammett ρ-values for the reactions of substituted 2-thiophenesulphonyl chlorides with aniline are in accord with the proposed mechanism. ?-Values for the reactions of 2-thiophenesulphonyl chloride with substituted anilines are related to the solvent effects by equation ? = ? 15.7 f(?) + 0.113E + 3.94. The solvent effects on these values can be interpreted by the effect of the dielectric constant and the influence of H-bonding. Mixed solvents are characterized by the presence of a maximum rate.     

Estimation of the alkaline earths metals by sequential titration with sodium tetraphenylborate

Summary Alkaline earths metals were titrated potentiometrically in the presence of polyethylene glycol with sodium tetraphenylborate. The sensor was a coated-graphite rod. The method can be used for the sequential estimation of barium, strontium, and calcium. The solubility of the precipitated species decreases with increasing atomic weight of the metals.

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Bestimmung von Erdalkalimetallen durch sequentielle Titration mit Natriumtetraphenylborat

Zusammenfassung Die Erdalkalimetalle wurden potentiometrisch in Gegenwart von Polyethylenglykol mit Natriumtetraphenylborat titriert. Als Sensor diente eine überzogene Graphitstabelektrode. Sequentiell können Barium, Strontium und Calcium bestimmt werden. Die Löslichkeit der Niederschläge nimmt mit ansteigendem Atomgewicht ab.

     

Coulometric titration of sulphide with mercury(II) in an ammoniacal buffer

An accurate method is described for the coulometric titration of low sulphide concentrations (8 × 10^?5–8 × 10^?3 M) with mercury(II) in a pH 9 ammoniacal buffer at room temperature. The electrochemical reactions involved are explained. Cyanide does not interfere at cyanide/sulphide ratios below 3. Accurate precise results were obtained for a lithopone sample.     

Reactions of hydrazidoyl chlorides with sodium N,N-dialkyldithiocarbamates

The reaction of N-arylbenzhydrazidoyl chlorides ( 1 ) with sodium N,N-dialkyldithiocarbamates yields the hydrazone derivatives 2 , which react further to form 4 unless the reaction sites are sterically crowded.     

自动电位滴定法测定磺酸盐合成及产品中硫酸钠

石油系磺酸盐合成及产品 (如凝土外加剂 )中硫酸盐的测定 ,对控制磺酸盐质量具有重要意义。目前 ,磺酸盐产品中硫酸盐测定多采用“混凝土外加剂匀质性试验方法”中硫酸钡重量法或离子交换重量法[1 ] ,此法手续繁琐 ,尤其是费时 ,周期约 48ｈ ,难以满足生产特别是工艺开发阶段条件试验时调整工艺参数的要求。用铅离子作滴定剂 ,铅离子选择性电极为指示电极 ,电位滴定法测定硫酸盐是一种比较可靠的方法 ;用于磺酸盐中硫酸盐的分析 ,目前尚未见报道。作者运用计算机控制的自动电位滴定法[2 ] ,选择了适合在磺酸盐中进行测定的滴定介质、酸度、…     

Indirect complexometric titration of sodium and potassium with EDTA

Summary Sodium is precipitated as sodium zinc uranyl acetate, filtered and dissolved in water, and zinc is titrated with EDTA using eriochrome black T as indicator. Potassium is precipitated as potassium sodium cobaltinitrite and dissolved in hot water containing little hydrochloric acid. The blue colored solution produced by cobalt in solution, with ammonium thiocyanate and acetone was titrated with EDTA until colorless. The results are good.The author is grateful to Prof. Philip W. West, Boyd Professor of Chemistry, Louisiana State University, for kindly providing the facilities to carry out the investigation.     

Nucleophilic substitution at sulphonyl sulphur part 3. Hydrolysis of substituted thiophene-2-sulphonyl chlorides catalysed by silver nitrate and silver nitrite salts

Hydrolysis reactions of substituted thiophene-2-sulphonyl chlorides (5-methyl, 5-H, 5-chloro, 5-nitro) catalysed by silver nitrate and silver nitrite salts have been studied in water at 25°. Salt effects by potassium nitrate, sodium perchlorate and mercuric bromide have also been investigated. For the catalysis effected with silver nitrate, the pseudo-first order rate constants depend on the first power of silver ion concentration, while nitrate anion is not involved in the transition state. The corresponding curved Hammett plot suggests a transition state with a partially developed sulphonylium character. With silver nitrite, the rate dependence on both silver and nitrite ion concentrations would indicate that silver is involved in the transition state as well as nitrite. Also, in this case the curved Hammett plot obtained suggests a partial positive charge on the sulphur atom in the transition state. A comparison with uncatalysed hydrolysis reactions would support a previous interpretation that thiophene-2-sulphonyl chlorides hydrolyze by an S_N2 type mechanism which can shift toward an S_N1 or an S_AN process depending on the ring substituent.     

Thermometric titration of cadmium with sodium diethyldithiocarbamate, with oxidation by hydrogen peroxide as indicator reaction

A new method of end-point indication is described for thermometric titration of cadmium with sodium diethyldithiocarbamate (DDTC). It is based on the redox reaction between hydrogen peroxide added to the system before titration, and the first excess of DDTC. Amounts of cadmium in the range 10-50 mumoles are titrated within 1% error.     

Monitoring lipid membrane translocation of sodium dodecyl sulfate by isothermal titration calorimetry

We establish high-sensitivity isothermal titration calorimetry (ITC) as a fast, reliable, and versatile tool for assessing membrane translocation of charged compounds. A combination of ITC uptake and release titrations can discriminate between the two extreme cases of half-sided binding and complete transbilayer equilibration on the experimental time scale. To this end, we derive a general fit function for both assays that allows for incorporation of different membrane partitioning models. Electrostatic effects are taken into account with the aid of Gouy-Chapman theory, thus rendering uptake and release experiments amenable to the investigation of charged solutes. This is exemplified for the flip-flop of the anionic detergent sodium dodecyl sulfate (SDS) across the membranes of 100-nm-diameter unilamellar vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in aqueous solution (10 mM phosphate buffer, 154 mM NaCl, pH 7.4). If repulsive electrostatic forces are accounted for adequately, SDS binding to POPC membranes can be evaluated on the basis of ideal mixing in all phases. At 25 degrees C, the intrinsic partition coefficient between the interfacial aqueous phase and the membrane amounts to 3.5 x 10(6); however, detergent flip-flop is negligibly slow under these conditions. Raising the temperature to 65 degrees C lowers the intrinsic partition coefficient to 1.4 x 10(6) but enables rapid transbilayer distribution of the detergent and, therefore, binding to or desorption from both membrane leaflets. Thus, combining a surface partition equilibrium with simple electrostatic theory appears highly useful in monitoring transmembrane movement of ionic compounds by ITC, thereby eliminating the need for specific reporter groups.     

Determination of phenytoin sodium injection and tablets by highly accurate nephelometric titration

A highly accurate nephelometric titration method was developed for the quantitative analysis of phenytoin sodium injection and tablets. The titration operating conditions and the validation of the method were studied. Five batches of phenytoin sodium injection and tablets were determined by the proposed method and the control experiment methods, respectively. The results of the titration are comparable to those of control experiments. The proposed method is accurate and reproducible, which is considered suitable for the quantitative analysis of a large number of samples.     

Investigation on drying conditions and assays of amidosulfuric acid and sodium carbonate by acidimetric coulometric titration and gravimetric titration

Amidosulfuric acid and sodium carbonate as standards for acid–base titrimetry were assayed by coulometric titration and gravimetric titration. Amidosulfuric acid was directly assayed by coulometric titration with electrogenerated hydroxide ions, and sodium carbonate was assayed by gravimetric back-titration. For sodium carbonate, excess amount of sulfuric acid, whose concentration was determined by coulometric titration, was added to sodium carbonate, and then gravimetrically back-titrated using a sodium hydroxide solution whose concentration was determined by gravimetric titration using the sulfuric acid. The accuracy of the coulometric titration for amidosulfuric acid and sulfuric acid was evaluated by examining the current efficiency of pulse electrolysis, the amount of the electrolysis current used, and the time spent for a titration. In addition, the drying conditions for high purity primary standards have a significant effect on the titration results due to changes in the acid–base assay. The suitable drying conditions for amidosulfuric acid and sodium carbonate were evaluated by mass-change measurements, coulometric titration and gravimetric titration. The measurement uncertainties were estimated from the uncertainties on the titration processes. Finally, the assays of amidosulfuric acid and sodium carbonate were 99.986% ± 0.010% (k = 2) after drying at 50 °C for 2 h, and 99.970% ± 0.016% (k = 2) after drying at 280 °C for 4 h, respectively. In addition, the international consistency was confirmed by measuring certified reference materials (CRMs) available from different National Metrology Institutes, and the compatibility of values among CRMs was experimentally ascertained.     

Oxidimetric estimation of chloramphenicol with aromatic sulphonyl monohaloamines

The reaction between chloramphenicol and chloramine-T, chloramine-B, bromamine-B or bromamine-T has been found to proceed quantitatively over a wide range of experimental conditions. Simple titrimetric procedures for the estimation of chloramphenicol with N-haloamines have been developed. Oxidation of the antibiotic involves a four-electron change and the products of oxidation have been identified. The methods are useful for the estimation of this antibiotic in medicinal formulations.