Spectrophotometric determination of ciprofloxacin in pure form and in tablets through charge-transfer complexation reactions

Three simple, quick and sensitive spectrophotometric methods are described for the determination of ciprofloxacin. The methods are based on the reaction of this drug as ann-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8,-tetracyanoquinodimethane (TCNQ) andp-chloranil (CL) as -acceptors to give highly coloured complex species. The coloured products are quantitated spectrophotometrically at 460, 843 and 550 nm for DDQ, TCNQ and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5–50, 1.5–15 and 20–200 g ml^–1 ciprofloxacin, but the concentration ranges for best accuracy are 10–48, 2.5–15 and 35– 195 g ml^–1 of drug for DDQ, TCNQ and CL, respectively. The relative standard deviations are less than 1.5%. Applications of the suggested methods to ciprofloxacin tablets are presented and compared with the USP method. The stability constants of the 11 DDQ and CL complexes were 1.086 × 10⁴ and 2.581 × 10⁴ lmol^–1, respectively, whereas for the 12 TCNQ complex it was 3.62 × 10⁸1. mol^–1.     

Quinone Imines with a Fused Azine Ring: III. Synthesis and Reactivity of 8-<Emphasis Type="Italic">p</Emphasis>-Tolylsulfonylimino-5,8-dihydroquinolin-5-one Derivatives

Unstable 8-p-tolylsulfonylimino-5,8-dihydroquinolin-5-one was generated by oxidation of the corresponding reduced form in acetic acid; it reacted in situ with hydrogen chloride and sodium p-toluenesulfinate to give the corresponding 6-substituted 5-hydroxy-8-aminoquinolines.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 124–127.Original Russian Text Copyright © 2005 by Belov, Nichvoloda.     

Kinetics and Mechanism of Oxidation of Some Substituted Benzhydrols by <Emphasis Type="Italic">N</Emphasis>-Bromosuccinimide

N-bromosuccinimide (NBS) oxidation of some substituted benzhydrols (4-Cl-, 4-Me-, 4-OMe-, 4-NO²⁻, 4,4′-dimethyl-, 4,4′-dichloro-, 4,4′-dimethoxy-, and 4-methyl-2-nitro-) yields corresponding benzophenones in the presence of Hg(OAc)₂. The reaction is first-order in [NBS], [substrate], and [H⁺]. A study on the primary kinetic hydrogen isotope effect and solvent isotope effect suggest that C-H and O-H stretching frequencies are affected in the transition state. Activation parameters for the rate-determining step have been evaluated. The results are in accord with the linear free energy relationship (LFER). The linear plot of log(k _obs/k ₀) vs. σ⁺ (ρ = −0.69)and Bunnett plots support the existence of proton-transfer in the rate-determining step. Rate behavior in different solvent compositions suggests dipolar-dipolar interaction in the absence of acid and ion-dipolar interaction in the presence of acid. Two different mechanisms have been suggested: cyclic transition state with unprotonated N-bromosuccinimide (NBS) in the absence of acid and noncyclic transition state with protonated NBS in the presence of acid.__________From Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 360–365.Original English Text Copyright © 2005 by Hiran, Malkani, Rathore.This article was submitted by the authors in English.     

A Study on the Photochemical Transformations of <Emphasis Type="Italic">p</Emphasis>- and <Emphasis Type="Italic">m</Emphasis>-Nitrosonitrobenzenes

Photochemical oxidation of p- and m-nitrosonitrobenzenes to corresponding dinitrobenzenes was studied. The reaction was described by a scheme involving two successive steps, with the rates of photochemical decomposition of isomeric nitrosonitrobenzenes being much higher than those of dinitrobenzenes. Oligomeric azo and azoxy compounds and the products of hydroxylation of the reaction medium were found as final products of the reaction upon long-term irradiation with UV light.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 4, 2005, pp. 287–292.Original Russian Text Copyright © 2005 by Zelentsov, Logunov.     

Condensation of <Emphasis Type="Italic">p</Emphasis>-Dimethylaminocinnamaldehyde with Aniline and Substituted Anilines in Micellar Media

Optimal conditions were found for the reactions of aniline and its hydroxy-, carboxy-, methyl-, and nitro-substituted derivatives with p-dimethylaminocinnamaldehyde in the presence of sodium dodecyl sulfate micelles in the pH range 1–6. A correlation was revealed between the optimal pH value pK _a of aromatic amines. The reaction in the model system aniline-p-dimethylaminocinnamaldehyde-sodium dodecyl sulfate in micelles formed by anionic surfactants is accelerated more than 1000-fold due to increased concentration of the reactive species in sodium dodecyl sulfate micelles.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 2, 2005, pp. 288–294.Original Russian Text Copyright © 2005 by Doronin, Chernova, Gusakova.     

New Tricyclic Amides. Synthesis,Structure, and Oxidation with Peroxyphthalic Acid

4-Azatricyclo[5.2.1.0^2,6]dec-8-ene was synthesized and brought into reactions with benzoyl, o-chlorobenzoyl, p-bromobenzoyl, p-, m-, and o-nitrobenzoyl, and bicyclo[2.2.1]hept-2-ene-endo-5,endo-6-dicarboximidoacetyl chlorides in chloroform in the presence of pyridine. The tricyclic amides thus obtained were epoxidated with peroxyphthalic acid prepared in situ by reaction of phthalic anhydride with a 35% aqueous solution of hydrogen peroxide. The structure of newly synthesized compounds was confirmed by IR and ¹H and ¹³C NMR spectroscopy and mass spectrometry. Their NMR spectra were compared with those of previously synthesized N-arylsulfonyl-4-azatricyclo[5.2.1.0^2,6]dec-8-enes on the basis of conformational composition of the corresponding p-nitrophenyl-substituted derivatives, which was determined by PM3 semi-empirical quantum-chemical calculations.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 837–845.Original Russian Text Copyright © 2005 by L. Kas’yan, Okovityi, Tarabara, A. Kas’yan, Bondarenko.     

<Emphasis Type="Italic">meso</Emphasis>-Phenyltetrabenzoazaporphyrins and Their Zinc Complexes. Synthesis and Spectral Properties

Zinc complexes of meso-phenyltetrabenzoazaporphyrins were prepared by the reaction of iso-indoline-1,3-diimine with phenylacetic acid in the presence of zinc oxide. Treatment of the products with sulfuric acid gave metal-free compounds.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 689–693.Original Russian Text Copyright © 2005 by Galanin, Kudrik, Shaposhnikov.     

Acetylation of 8-Bromo-5-hydroxy-6,7,4′-trimethoxyflavone

5-Hydroxy-6,7,4′-trimethoxyflavone was isolated from Centaurea pseudomaculosa Dobrocz., and its bromo derivative was obtained. The reaction of 8-bromo-5-hydroxy-6,7,4′-trimethoxyflavone with acetic anhydride in the presence of a catalytic amount of p-toluenesulfonic acid gave of a 73% 5-acetoxy-8-bromo derivative whose structure was established by X-ray diffraction.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 999–1001.Original Russian Text Copyright © 2005 by Donbaeva, Yamovoi, Tuleuvov, Turdybekov, Gatilov, Adekenov.     

Reductive Acylamination of Pyridine <Emphasis Type="Italic">N</Emphasis>-Oxide with Aminopyridines and Their <Emphasis Type="Italic">N</Emphasis>-<Emphasis Type="Italic">p</Emphasis>-Tolylsulfonyl Derivatives

Pyridine N-oxide reacts with 2- and 3-aminopyridines and their N-p-tolylsulfonyl derivatives in alkaline medium in the presence of p-toluenesulfonyl chloride to give N-p-tolylsulfonyl-2,2′- and 2,3′-dipyridylamines, respectively, as a result of reductive acylamination. In the reactions with 4-aminopyridine and 4-p-tolylsulfonyl-aminopyridine, their N-p-tolylsulfonyl- and N,N-bis(p-tolylsulfonyl) derivatives are formed, while reductive acylamination does not occur.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 128–130.Original Russian Text Copyright © 2005 by Solekhova, Kurbatov.     

Mechanism of OH radical-induced oxidation of <Emphasis Type="Italic">p</Emphasis>-cresol to <Emphasis Type="Italic">p</Emphasis>-methylphenoxyl radical

The OH radical-induced oxidation of p-cresol to p-methylphenoxyl radical was studied in aqueous solution in a wide pH range by means of pulse radiolysis combined with optical spectroscopy. OH-adduct cyclohexadienyl type radicals were identified as intermediates of the reaction. In the acidic pH range the first-order rate coefficient of phenoxyl radical formation was found linearly dependent on the H₃O⁺ concentration yielding a bimolecular rate coefficient of 1.8 × 10⁸ mol^–1 dm³ s^–1. In the alkaline range a linear dependence was found on the OH^– concentration with rate coefficient of 4.9 × 10¹⁰ mol^–1 dm³ s^–1. These findings were interpreted in terms of acid-base catalysis of the H₂O elimination from the OH-adduct. With the time resolution applied, 30 ns, the radical cation p-CH₃C₆H₄OH^+. was not observed as intermediate.     

Studies on Mononuclear Chelates Derived from Substituted Schiff Bases Ligands (Part 3). Synthesis and Characterization of a New 5-Nitrosalicylidene-<Emphasis Type="Italic">p</Emphasis>-aminoacetophenoneoxime and Its Complexes with Co(II), Ni(II), Cu(II), and Zn(II)

A new ligand, 5-nitrosalicylidene-p-aminoacetophenoneoxime (HL), was synthesized from p-aminoacetophenoneoxime and 5-nitrosalicylaldehyde under reflux in absolute EtOH at 60°C for 3 h. Mononuclear complexes with a metal : ligand ratio of 1 : 2 were prepared with Co^II, Ni^II,Cu^II, and Zn^II salts. Their structures were determined on the basis of elemental analyses, IR, ¹H and ¹³C NMR, electronic spectra, magnetic susceptibility measurements, molar conductivity, and thermogravimetric analyses. According to the results, two ligands were suggested to be coordinated to each metal atom by phenolic oxygen and imino nitrogen to form high-spin tetrahedral complexes with cobalt(II), nickel(II), and copper(II) while forming a diamagnetic complex with zinc(II).__________From Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 441–445.Original English Text Copyright © 2005 by Canpolat, Kaya.This article was submitted by the authors in English.     

Pentacyclic triterpenes from <Emphasis Type="Italic">Sarcostemma clausum</Emphasis>

A homologous series of alkanoic acid (C₂–C₅) esters of germanicol was isolated from the methanolic extract of Sarcostemma clausum, of which germanicol-3-propionate and 3-pentanoate have not been previously described in the literature. In addition, taraxasterol, multiflorenol, and bauerenol were also isolated for the first time from the genus Sarcostemma. Structures were elucidated by chemical and spectroscopic methods (NMR, IR, SM) and by comparison with literature data.Published in Khimiya Prirodnykh Soedinenii, No. 6 pp. 464–466, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis of 4-[(1<Emphasis Type="Italic">R</Emphasis>,4<Emphasis Type="Italic">R</Emphasis>)-3-Oxo-<Emphasis Type="Italic">p</Emphasis>-menthan-2-ylidenemethyl]benzoic Acid and Its Esters

Carbonylation of (E)-2-(4-halobenzylidene)-p-menthan-3-ones, catalyzed by PdCl₂(PPh₃)₂, gave a distereometric mixure of 4-[(1R,4R)- and (1R,4S)-3-oxo-p-menthan-2-ylidenemethyl]benzoic acids, whose reaction with phenols gave 1R,4R diastereomers of the corresponding esters.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 659–664.Original Russian Text Copyright © 2005 by Drushlyak, Kutulya, Pivnenko, Vashchenko.     

Hydrolyzed Tannin from <Emphasis Type="Italic">Euphorbia glareosa</Emphasis> Leaves

Hydrolyzed tannin (I), the structure of which was established using chemical investigations and UV, IR, PMR and ¹³C NMR spectra, was isolated from Euphorbia glareosa leaves.__________Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 250–251, May–June, 2005.     

Mechanism of Depolymerization of Polymeric <Emphasis Type="Italic">p</Emphasis>-Dinitrosobenzene in Vulcanization of Unsaturated Rubbers: A Quantum-Chemical Study

The mechanism of depolymerization of polymeric p-dinitrosobenzene in vulcanization of unsaturated rubbers is analyzed. The results obtained explain why the vulcanizing activity of p-dinitrosobenzene decreases in the course of its prolonged storage.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 320–323.Original Russian Text Copyright © 2005 by Klyuchnikov, Chachkov, Deberdeev, Zaikov.     

<Emphasis Type="Italic">peri</Emphasis>-Naphthylenediamines: XXXIX. Synthesis and Structure of <Emphasis Type="Italic">N,N′,N′</Emphasis>-Trimethyl-<Emphasis Type="Italic">N</Emphasis>-nitrosonaphthalene-1,8-diamine Derivatives

The corresponding N-nitroso derivatives were synthesized by the action of nitrous acid on N,N,N′-trimethylnaphthalene-1,8-diamine, N,N,N′-trimethyl-5-nitronaphthalene-1,8-diamine, and N,N,N′-trimethylacenaphthene-5,6-diamine, and molecular structure of the products was studied.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1020–1027.Original Russian Text Copyright © 2005 by Koroleva, Dyablo, Pozharskii, Sennikova, Starikova.     

Mechanism of Replacement of the Nitro Group and Fluorine Atom in <Emphasis Type="Italic">meta</Emphasis>-Substituted Nitrobenzenes by Phenols in the Presence of Potassium Carbonate

The relative mobilities of the nitro group and fluorine atom in 1,3-dinitrobenzene and 1-fluoro-3-nitrobenzene by the action of phenols in the presence of potassium carbonate in dimethylformamide at 95–125°C were studied by the competing reaction method. The rate constant ratios k(NO₂)/k(F) were correlated with the differences between the corresponding activation parameters (ΔΔH ^≠ and ΔΔ S ^≠). The greater mobility of the nitro group was found to be determined by the entropy control of the reactivity of arenes. The activation parameters (ΔH ^≠ and ΔS ^≠) were calculated, and the enthalpy-entropy compensation effect was revealed. The reaction mechanism is discussed.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 999–1005.Original Russian Text Copyright © 2005 by Khalfina, Vlasov.     

Synthesis of Heterocycles from Arylation Products of Unsaturated Compounds: XIII. 5-R<Superscript>1</Superscript>-Benzyl-2-(R<Superscript>2</Superscript>-2-pyridylimino)thiazolidin-4-ones

Meerwein reactions of arenediazonium bromides with methyl and ethyl acrylates gave 3-aryl-2-bromopropionic acid esters which were subjected to cyclocondensation with N-(2-pyridyl)- and N-(6-methyl-2-pyridyl) thioureas to obtain 5-R¹-benzyl-2-(R²-2-pyridylimino)thiazolidin-4-ones. The latter were shown to exist in solution as E isomers of the imino form.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1071–1075.Original Russian Text Copyright © 2005 by Matiichuk, Obushak, Tsyalkovskii.     

Synthesis and Functionalization of 3-Ethylquinoxalin-2(1<Emphasis Type="Italic">H</Emphasis>)-one

A new and effective procedure was developed for the synthesis of 3-ethylquinoxalin-2(1H)-one from o-phenylenediamine and ethyl 2-oxobutanoate. The latter was prepared by the Grignard reaction of diethyl oxalate with ethylmagnesium bromide or iodide. The ethyl group in 3-ethylquinoxalin-2(1H)-one can readily be converted into various functional groups: α-bromoethyl, α-thiocyanato, α-azidoethyl, α-phenylaminoethyl, acetyl, and bromoacetyl. The reaction of 3-(bromoacetyl)quinoxalin-2(1H)-one with thiourea and hydrazine-1,2-dicarbothioamide gives the corresponding 3-(2-amino-4-thiazolyl) derivatives.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 4, 2005, pp. 609–616.Original Russian Text Copyright © 2005 by Mamedov, Kalinin, Gubaidullin, Isaikina, Litvinov.     

Mechanism of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>-catalyzed olefin hydroalumination by alkylalanes

The composition of intermediates of the Cp₂ZrCl₂-catalyzed hydroalumination of α-olefins by isobutylalanes (HAlBuⁱ ₂, AlBuⁱ ₃, ClAlBuⁱ ₂) was studied by dynamic ¹H and ¹³C NMR pectroscopy. The reaction of Cp₂ZrCl₂ with isobutylalanes affords the complex (Cp₂ZrHCl·HAlBuⁱ ₂)₂ responsible for α-olefin hydroalumination.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 311–322, February, 2005.