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91.
Procedures are described for the determination of organic compounds with iodine trichloride under Andrews's titration conditions. Samples are directly titrated with iodine trichloride or first reacted with an excess of iodine monochloride, with subsequent titration of the iodine formed. The direct titration is done initially in feebly acid medium, then the acidity is raised (biotin, methionine, cystine and thiomersal). Pre-oxidation with iodine monochloride is used if the organic compound reacts slowly [tryptophan and arsenic(III) compounds] or is determined in bicarbonate medium (hydroxylamine and thiosemicarbazide). The ferrocyanide formed by the reduction of ferricyanide (by thiourea and allylthiourea) can also be titrated. Arsenic(V) compounds are determined after reduction to arsenic(III), and iodine in organic compounds is converted into iodide by alkaline fusion into iodide and the iodide titrated. 相似文献
92.
Devendra Kumar Uday Razdan Alka D. Gupta 《Journal of polymer science. Part A, Polymer chemistry》1992,30(7):1477-1487
Various melt-polymerizable bisimido-bisphthalonitrile polymer precursors were synthesized by the reaction of 4-aminophthalonitrile (4-APN) with bis(3,4-dicarboxyphenyl) dimethylsilane dianhydride (SIDA), 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), bis(3,4-dicarboxyphenyl)ether dianhydride (ODPA), and 3,3′, 4,4′-tetracarboxylichenzophen+ne dianhydride (BTDA) in an aprotic solvent. The synthesized monomers showed crystalline melting at 269 and 271°C. Elemental analysis, differential thermal analysis (DTA), infrared (IR), nuclear magnetic resonance (1H-NMR) and mass spectral studies were carried out to characterize the synthesized monomers. Thermogravimetric analysis (TGA) of the synthesized monomers showed their thermal stability at 410–400°C. A detailed study and NMR investigation of the first step of condensation reaction was carried out and indicated the formation of a transient charge transfer complex. Thermal cyclization of the formed intermediate, however, gave the required monomers. A preliminary study demonstrated that melt-polymerization of the synthesized monomers gave thermallystable, tough polymers. 相似文献
93.
A simple and rapid alkalimetric method for the determination of mercaptans through trithiocarbonic acid formation is described. The mercaptans are titrated in tert.-butanol in the presence of carbon disulphide with standard aqueous sodium hydroxide, with phenolphthalein as indicator. The -SH group is smoothly, rapidly and quantitatively transformed into the group under the specified conditions. The method has been extended to the analysis of mercaptan-carboxylic acid and mercaptan-trithiocarbonate mixtures. 相似文献
94.
An amperometric titration method is described for the determination of 1-5 mg of organic isothiocyanates, based on their quantitative reaction with n-butylamine in dimethylfonnamide to form N,N-disubstituted thioureas which are then titrated amperometrically in aqueous ammonia-ammonium nitrate buffer with silver nitrate (dropping mercury electrode at -0.56V). The end-point corresponds to a silver:thiourea ratio of 2:1, with precipitation of silver sulphide. The method is simple, accurate, widely applicable, and gives reproducible results. 相似文献
95.
Cerium and lanthanum were determined gravimetrically by selective precipitation with N-m-tolyl-m-nitrobenzohydroxamic acid and separated from several metal ions such as Ag(+), Be(2+) , Pb(2+) , Mn(2+) , Cu(2+), Zn(2+) , Cd(2+) , Hg(2+) , Pd(2+) , Ga(3+) A1(3+) , Bi(3+) , Sb(3+), Sn(4+), Ce(3+) , Pr(3+) , Nd(3+) , Ti(4+), Zr(4+), Th(4+), V(5+) , Mo(6+) and U(6+) . The precipitates were weighted directly after drying at 110 degrees . The analytical results indicated the composition of the complexes to be (C(14)H(11)N(2)O(4))(n)M. 相似文献
96.
97.
Nitrite diazotizes sulphanilamide, which then does not undergo 3,5-dibromination. Nitrite can therefore be determined by reaction with excess of sulphanilamide, the surplus of which is then titrated with o-iodosobenzoate or chloramine-T in the presence of potassium bromide, with Methyl Red as indicator. Mixtures of iodide and bromide can be analysed by oxidation of the iodide with excess of o-iodosobenzoate at pH 4-6, followed by extraction of the iodine (which is then titrated with thiosulphate) and then oxidation of the bromide in dilute sulphuric acid medium in the presence of sulphanilamide as bromine scavenger, the residual oxidant being evaluated iodometrically. 相似文献
98.
BaSeO3·2·5H2O(I), PbSeO3· 2H2O(II) and CdSeO3·3.5H2O(III) were prepared and analysed. Their hygroscopicity and solubility was investigated. These compounds have high thermal Stability, as shown by their TG and DTA data. IR spectra show multi-dentate coordination of selenite to cations, due to considerable splitting of the asymmetric v3 and v4 bands of SeO
3
2
– in the 780-730 cm–1 and 420-325 cm–1 region.Tentative structures have been proposed involving bridging oxygen atoms.
Zusammenfassung BaSeO3-2.5H2O(I), PbSeO3 · 2H2O(II) und CdSeO3· 3.5H2O(III) wurden hergestellt, analysiert sowie deren Hygroskopizität und Löslichkeit untersucht. TG- und DTA-Untersuchungen erweisen die hohe thermische Stabilität dieser Verbindungen. Die IR-Spektren zeigen mehrzählige Koordination von Selenit zu Kationen, was aus einer beträchtlichen Aufspaltung der antisymmetrischenv 3 undv 4 Banden von SeO 3 2 – im Bereich 780-730cm–1 bzw. 420-325 cm–1 hervorgeht. Es wurden versuchsweise Strukturen mit überbrückenden Sauerstoffatomen vorgeschlagen.
BaSeO3· 2,5H2O, PbSeO3 · 2H2O CdSeO3 · 3,5H2O . . - , v 3 v 4 SeO 3 2 }- 780-730 420-325 –1. , .相似文献
99.
E. Santoyo R. García R. Abella A. Aparicio S. P. Verma 《Journal of chromatography. A》2001,920(1-2):325-332
A new application of capillary electrophoresis for measuring major and trace anions in thermal water and condensed-steam samples is presented. Ten fluid samples were collected from hydrothermal springs and fumaroles located in a volcanic zone of Deception Island, Antarctica. Anion separation was achieved in less than 6 min using indirect UV detection at 254 nm with a negative power supply (−15 kV). The electrolyte consisted of 4.7 mM sodium chromate, 4.0 mM electroosmotic flow modifier (OFM) hydroxide, 10 mM 2-(N-cyclohexylamino)ethanesulfonic acid and 0.1 mM calcium gluconate (pH 9.1). Major anions (Cl−, SO42, PO4H2−, and CO3H−) were measured using hydrostatic injection (10 cm for 30 s) at 25°C. Trace amounts of anions (F−, Br−, and NO3−) were better determined by electromigration injection (4 kV, 10 s) at 15°C. Good reproducibility of the migration times (<0.72% RSD), a satisfactory linear response and accuracy as well as acceptable detection limits were successfully obtained. 相似文献
100.
The efficient, regioselective synthesis of functionalized/annulated quinolines was achieved by the coupling of 2‐aminoaryl ketones with alkynes/active methylenes/α‐oxoketene dithioacetals promoted by InCl3 in refluxing acetonitrile as well as under solvent‐free conditions in excellent yields. This transformation presumably proceeded through the hydroamination–hydroarylation of alkynes, and the Friedländer annulation of active methylene compounds and α‐oxoketene dithioacetals with 2‐aminoarylketones. In addition, simple reductive and oxidative cyclization of 2‐nitrobenzaldehyde and 2‐aminobenzylalcohol, respectively, afforded substituted quinolines. Systematic optimization of the reaction parameters allowed us to identify two‐component coupling (2CC) conditions that were tolerant of a wide range of functional groups, thereby providing densely functionalized/annulated quinolines. This approach tolerates the synthesis of various bioactive quinoline frameworks from the same 2‐aminoarylketones under mild conditions, thus making this strategy highly useful in diversity‐oriented synthesis (DOS). The scope and limitations of the alkyne‐, activated methylene‐, and α‐oxoketene dithioacetal components on the reaction were also investigated. 相似文献