In Process Citation

A microdetermination of iodide in waters and organic materials is based on oxidation with hydrogen peroxide to iodine which gives a blue colour with o-tolidine at pH 3.5-4.5. The sensitivity is 0.02 mug/ml.     

Titrimetric determination of microgram amounts of bismuth after precipitation as Bi[Cr(SCN)(6)] followed by thiocyanate amplification

Bismuth (10-100 mug) is precipitated as Bi[Cr(SCN)(6)]. After filtration, the precipitate is treated with bicarbonate solution, and the thiocyanate dissolved is oxidized by iodine in alkaline medium to sulphate. After acidification, the excess of iodine is extracted into chloroform, and the iodide in the aqueous solution is amplified by bromine oxidation and subsequent treatment with more iodide. The titrimetric procedure provides 228 iodine atoms for each original bismuth ion. Only Hg(2+)(2), Hg(2+) and AsO(3-)(4) interfere seriously.     

New spectrophotometric methods for determination of captopril bulk drug and tablets

Three simple, rapid and sensitive methods for the assay of captopril which is an effective alternative to digitalis were developed. These methods are based on the oxidation reaction in aqueous solution of captopril with either ferric chloride or iodine. The indirect quantitation of the product was carried out at 523, 351 and 620 nm for ferro-bipyridyl, residual iodine and residual iodine-starch complex, respectively. All variables were studied to optimize the reaction conditions. Regression analysis of Beer's plot showed good correlation in a general concentration range of 0.25-25 mug captopril/ml. No interference was observed from hydrochlorothiazide diuretic which was recently introduced in combination with captopril or other common pharmaceutical adjuvants. The validity of the methods was tested by analysing capoten and capozide tablets. Recoveries were 99.1-102.8%.     

有机合成中的高价碘应用

高价碘化物作为一种性能温和、选择性强及环境友好的氧化试剂在有机合成中得到了广泛的应用。近年来,各种不同结构的高价碘试剂和各种新的反应及应用大量涌现出来,使它们的应用领域从传统的醇类氧化扩展到一些结构复杂化合物的合成领域当中。本文以最常用和研究较多的几个高价碘化合物为例,对它们用于有机合成反应,如氧化、加成、取代和重排的最新进展进行了概述,对本研究小组重点研究的五价碘化合物邻羟基苯碘酰与酮类化合物的取代反应和烯烃化合物的加成反应也作了介绍。     

Titrimetric microdetermination of salicylic, acetylsalicylic, and p-hydroxybenzoic acids by amplification reactions

A novel titrimetric method with amplification has been developed for the determination of 0.05–2.0 mg of salicylic, acetylsalicylic, or p-hydroxybenzoic acid. It depends on bromination of these compounds by bromine to tribromophenylhypobromite, which liberates iodine when treated with iodide. The liberated iodine is extracted with chloroform, reduced to iodide, oxidation of the resulting iodide with bromine, and iodometric titration of the iodate produced gives the sixfold amplification method. The coefficient of variation does not exceed 1% for above 0.5 mg of the studied compounds, but increases to 2.8% at the 0.05-mg level.     

Formation of peroxide compounds on the oxidation of lignin by oxygen in an organic solvent

The results are given of a determination of the steady-state concentrations of peroxide compounds on the oxidation of lignin by oxygen in dioxane. An iodometric method of determining peroxides was used, with spectrophotometric control of the amount of iodine formed. It was established that the achievable steady-state concentration of peroxide compounds on the oxidation of lignin is 0.28–0.44 wt. % of O_act (oxygen pressure 1 atm, temperature 50–80°C). With a rise in the temperature, the steady-state concentration of peroxide compounds decreased. The addition of water (30 vol. %) to the organic solvent led to an increase in the rate of accumulation of peroxide compounds. It has been shown that the presence of alkaline and acidic catalysts exerts no appreciable influence on the achievable steady-state concentration and the rate of accumulation of peroxide compounds during the oxidation of lignin.Bratsk Industrial Institute. All-Union Scientific Production Combine of the Pulp and Paper Industry, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 413–417, May–August, 1992.     

Spectrophotometric Determination of Some Pharmaceutically Active Amides and Imides

Abstract

The determination of nicotinamide, alloxan, saccharin, barbitone and theobromine is achieved by a simple and rapid spectrophotometric method. The proposed method depends on the bromine oxidation of the amide or imide functional groups with the formation of N - bromoamide or N - bromoimide respectively, having a positive bromine atom. The oxidation products oxidize iodide ions to iodine which is measured as its starch complex.

The method is suitable for the determination of : 0.08–0.4, 0.5–5, 20–80, 25–200 and 50–400 mg with a mean accuracy (P′ = 0.05) of 99.29 ± 1.39%, 101.36 ± 1.44 %, 101.28 ± 1.85 %, 99.94 ± 1.24 % and 100.82 ± 1.29 % for the mentioned compounds respectively.     

The case for the intermediacy of monomeric metaphosphate analogues during oxidation of H-phosphonothioate, H-phosphonodithioate, and H-phosphonoselenoate monoesters: mechanistic and synthetic studies

Studies on the reaction of H-phosphonothioate, H-phosphonodithioate, and H-phosphonoselenoate monoesters with iodine in the presence of a base led to identification of a unique oxidation pathway, which consists of the initial oxidation of the sulfur or selenium atom in these compounds, followed by oxidative elimination of hydrogen iodide to generate the corresponding metaphosphate analogues. The intermediacy of the latter species during oxidation of the investigated H-phosphonate monoester derivatives with iodine was supported by various diagnostic experiments. The scope and limitation of these oxidative transformations for the purpose of the synthesis of nucleoside phosphorothioate, nucleoside phosphorodithioate, and nucleoside phosphoroselenoate diesters was also investigated.     

Determination of sulphur functions with N-iodosuccinimide

Titrimetric determination of thioureas, thiols, xanthates and dithiocarbamates with N-iodosuccinimide (NIS) is described. The method for xanthate can be applied to carbon disulphide (converted into xanthate with potassium ethoxide). Acidic and non-aqueous solutions of the oxidizing agent are stable. The procedures are rapid and accurate to 0.1% with a precision of 0.2%. Hydrogen sulphide and thiocarbonyl compounds interfere. The behaviour of N-bromosuccinimide and NIS with thiols in aqueous medium is compared. It is shown that iodine is the oxidizing species in both cases. The limitations of iodine as a reagent for thiol determination are discussed. Cysteine, which cannot be determined with iodine, can be determined with NIS. The role of methanol in non-aqueous determination of thiols is discussed. Methanol accelerates the oxidation, which is otherwise slow in acetonitrile medium.     

Flow injection fluorimetric determination of thiamine and copper based on the formation of thiochrome

The reaction, involving the oxidation of thiamine by copper(II) in basic solutions to fluorescent thiochrome, has been adapted to the determination of thiamine by flow-injection analysis. Linear calibration graphs are obtained between 0.30 and 6.02 mug/ml with a sampling rate of 50 samples/hr and a relative standard deviation of 0.53%. This reaction has also been adapted to the determination of copper(II) over the range 0.5-5.0 mug/ml. The applicability of both methods for determination of thiamine and copper is demonstrated by investigating the effect of potential interferences and by the analysis of real samples (pharmaceuticals for thiamine and ores and alloys for copper).     

New chiral hypervalent iodine(V) compounds as stoichiometric oxidants

The synthesis and application of some new hypervalent iodine compounds bearing chiral and achiral ester motives derived from easily accessible starting materials is presented. The oxidation is carried out using dimethyldioxirane as an oxidant providing the desired compounds in moderate to high yields. A crystal structure analysis for one iodine(V) derivative is investigated. The λ⁵-iodanes are applied as stoichiometric reagents in the oxidation of thioanisole to phenylmethyl sulfoxide, benzyl alcohol to benzaldehyde, and meso-hydrobenzoine to benzaldehyde, benzyl, and benzoin.     

Combined ultraviolet-fluorescence detection in high-pressure liquid chromatography of pharmaceuticals.

The use of combined UV-fluorescence detection for the evaluation of incompletely resolved compounds and trace components in the presence of large quantities of major components is described, analysis for thioridazine and some of its oxidation products by high-pressure liquid chromatography being chosen as a practical example. Mesoridazine and the ring oxide of thioridazine have been determined quantitatively with relative standard deviations (n = 6) of 2.0 and 3.6%, respectively, at concentrations below 0.1 mug per injection. Resolution of the two components is difficult and, in this instance, unnecessary. By a similar approach, it was possible to determine the highly fluoresecent sulforidazine at a concentration of 0.4% of the thioridazine with 6.2 mug of thioridazine injected. A relative standard deviation of 5% was attainable at this concentration. Fluorescence detection limits for mesoridazine and sulforidazine at a signal-to-noise ratio of 4:1 are between 5 and 10 ng per injection; this corresponds to about 0.1% of the active substance for the above example.     

Titrimetric determination of phenol resorcinol and phloroglucinol

A new and sensitive titrimetric method with an amplification procedure has been worked out for the determination of 10-1000 mug of phenol, resorcinol or phloroglucinol. The method is based on reaction of the phenols with an excess of bromine to form bromosubstituted aryl hypobromites. After removal of excess of bromine with formic acid, the hypobromites are treated with iodide to liberate an equivalent amount of iodine, which is extracted into chloroform, then reduced to iodide and determined by the Leipert procedure with 6-fold amplification. The coefficient of variation does not exceed 0.4% for amounts of determinand > 100 mug, but increases to 1.5% at the 10-mug level.     

Titrimetric determination of thiocyanate and thiosulphate ions by oxidation with iodine in alkaline solution

Thiocyanate (2.7-90 mug) and thiosulphate (4.5-90 mug) ions are oxidized by iodine in alkaline media to sulphate ions. After acidification, the excess of iodine is extracted into chloroform, and the iodide ions formed in the redox reaction subjected to an amplification reaction. Either a titrimetric or a spectrophotometric finish may be used. Each thiocyanate and thiosulphate ion results in the ultimate production of 19 and 24 iodine molecules, respectively.     

有机合成中有机高价碘化合物的研究进展

对高价碘化合物用于有机合成反应，如氧化，加成，取代和交叉偶联的最新进展进行了评述，参考文献82篇。     

三价碘试剂促进的氧化反应研究进展

三价碘试剂的反应性能类似于过渡金属如汞、钛和铅,并且具有环境友好、价值低廉、反应条件温和、反应后处理简单和商业可利用的特点,因此在有机合成中得到广泛应用,特别是作为一种高效的选择性氧化试剂,受到广大有机化学工作者的亲睐。本文就三价碘试剂促进的氧化反应,从醇的氧化、羰基化合物的氧化官能团化到氧化硒化和铋化等14类反应进行了简单的综述。     

Determination of d-biotin at the microgram level

The iodate formed in the reaction of d-biotin with periodate is determined by reacting it with iodide and titrating the iodine with thiosulphate (to determine 90-950 mug of biotin), or the tri-iodide is measured spectrophotometrically to determine 20-80 mug of the test compound. Excess of periodate is masked with molybdate.     

FIA-spectrophotometric determination of N-substituted phenothiazine derivatives by oxidation with a solid-phase reactor of manganese dioxide incorporated in polyester resin beads

The determination of several N-substituted phenothiazine derivatives was carried out by the reaction of the drug with managanese dioxide entrapped in a polymeric material in a packed-bed reactor; the oxidized drug was monitored at lambda(max). The calibration graph is linear over the range 5-50 mug/ml of phenothiazine derivatives with a relative standard deviation of 0.5-1% (at 10 mug/ml) and sample throughput of 40-48 h(-1). The influence of foreign compounds was studied and the method was applied to the determination of six different phenothiazine derivatives in pharmaceutical formulations.     

Mechanistic Insights on the Iodine(III)‐Mediated α‐Oxidation of Ketones

The synthesis of α‐substituted carbonyl compounds is of great importance due to their ubiquity in both natural and man‐made biologically active compounds. The field of hypervalent iodine chemistry has been a great contributor to access these molecules. For example, the α‐oxidation of carbonyl compounds has been one of the most investigated iodine(III)‐mediated stereoselective transformations. Yet, it is also the transformation that has met the most challenge in terms of achieving high stereoselectivities. The different mechanistic pathways of the iodine(III)‐mediated α‐tosyloxylation of ketones have been investigated. The calculations suggest an unprecedented iodine(III)‐promoted enolization process. Indications that iodonium intermediates could serve as proficient Lewis acids are reported. This concept could have broad impact and foster new developments in the field of hypervalent iodine chemistry.     

An environmentally benign benzylic oxidation catalyzed by hypervalent iodine intermediate in water

An effective and environmentally benign benzylic oxidation for transition of alkylarenes into the corresponding carbonyl compounds was reported.Alkylarenes were mixed and stirred with potassium bromide,m-chloroperbenzoic acid and a catalytic amount of iodobenzene in water at 60 8C for several hours,a series of the corresponding carbonyl compounds was obtained in moderate to good yields.In the reaction,iodobenzene was first oxidized by m-chloroperbenzoic acid into the hypervalent iodine intermediate which then reacted with potassium bromide to form the key radical initiator for the benzylic oxidation.