Quantitative Determination of Miconazole in Creams by Second Order Derivative Spectrophotometry

ABSTRACT

A derivative spectrophotometry was developed to determine miconazole in cream formulations that contain benzoic acid as preservative. The procedure was based on the linear relationship in the range 100-500 μg ml^?1 between the drug concentration and the second derivative amplitudes at 276 nm. Results of the recovery experiments performed on various amounts of benzoic acid and of the determination of miconazole in cream confirmed the applicability of the proposed method to complex formulations.     

Determination of hydroxyl radical by capillary electrophoresis and studies on hydroxyl radical scavenging activities of Chinese herbs

High-performance capillary electrophoresis (CE) with electrochemical detection (ED) was employed to determine hydroxyl radicals in the Fenton reaction. Hydroxyl radicals can react with salicylic acid to produce 2,3-dihydroxy benzoic acid and 2,5-dihydroxy benzoic acid, which can be analyzed by CE-ED. Based on this principle, hydroxyl radicals were determined indirectly. In a 20 mmol/L phosphate running buffer (pH 7.4), 2,3-dihydroxy benzoic acid and 2,5-dihydroxy benzoic acid would elute simultaneously from the capillary within 6 min. As the working electrode, a 300 m diameter carbon-disk electrode exhibits good responses at +0.60 V (vs. SCE) for the two analytes. Peak currents of the two analytes are additive. Excellent linearity was obtained in the concentration range from 1.0×10^-3 mol/L to 5.0×10^-6 mol/L for 2,3-dihydroxy benzoic acid. The detection limit (S/N=3) was 2.0×10^-6 mol/L. This method was successfully applied for studying hydroxyl radical scavenging activities of Chinese herbs. It is testified that Apocynum Venetum L., Jinkgo bibola L., Morus alba L. and Rhododendron dauricum L. have strong hydroxyl radical scavenging activities.     

Recognition of anions and monocarboxylic acids by a fluorescent guanidine-based receptor

A guanidine-based fluorescent receptor has been synthesised to study its binding behaviour towards anions (F^? , Cl^? , Br^? , I^?  and AcO^? ). The two donor N–H bonds of the receptor do not point in the same direction; rather, one N–H bond is intramolecularly hydrogen-bonded with the carbonyl oxygen atom. The nature of the donor–acceptor (DA) arrangement induces moderate binding properties. The binding behaviour towards monocarboxylic acids (benzoic acid and phenylacetic acid) is also compared. The binding behaviour of receptor 1 towards the F^?  anion is higher among the anions studied, whereas in the case of monocarboxylic acid, the binding constant with phenylacetic acid is higher than benzoic acid.     

Formation of sulfines in the peroxyacid oxidation of neopentyl neopentanethiolsulfinate

Low temperature ¹H NMR and ¹³C NMR, and IR suggest that the $\text{m}$-chloroperbenzoic acid (MCPBA) oxidation of neopentyl neopentanethiolsulfinate leads to the formation of (E)- and (Z)-2,2-dimethylpropanethial S-oxide, neopentyl neopentanethiolsulfonate, and other products.     

Rate constants for the reactions of isobutyl,neopentyl, cyclopentyl,and cyclohexyl radicals with molecular oxygen

Rate constants have been measured for the reactions of four hydrocarbon radicals with O₂ in the gas phase at room temperature. Laserflash photolysis was used to generate low concentrations of radicals. A photoinization mass spectrometer followed the radical loss as a function of time. The measured pseudo first-order decay rate of the radical and the absolute oxygen concentration were combined to give the absolute rate constants (in units of 10^?12 cm³ molec^?1 s^?1): isobutyl (2.9 ± 0.7); neopentyl (1.6 ± 0.3); cyclopentyl (17 ± 3); and cyclohexyl (14 ± 2). The cycloalkyl radicals have rate constants similar to those of other secondary radicals. However, the isobutyl and neopentyl radicals react more slowly than similar primary radicals. These new rate constants are compared in Figure 2 with the recently published correlation of reactive cross section with radical ionization potential.     

KINETICS AND MECHANISM OF COMPLEX FORMATION BETWEEN [PtCl(DIEN)]+ AND THIOLS AND THIOETHERS

Abstract

Reactions of the monofunctional platinum(II) complex, [PtCl(dien)]⁺, with different thiols and thioethers, including biologically important molecules, have been studied as a function of temperature (288.2–308.2K) using conventional electronic spectrophotometry in 0.10 M aqueous hydrochloric acid and by ¹H NMR spectroscopy. The second-order rate constants, k₂, are similar, varying between 1.43 × 10^?3 and 46.1 × 10^?3 M^?1s^?1 at 25°C. The reactivity follows the sequences: D-penicillamine ≤ L-cysteine ≤ glutathione ≤ thiodiglycolic acid ≤ thioglycolic acid ≤ L-methionine ≤ S-methylthioglycolic acid ≤ glycyl-D,L-methionine. However, variation in size, bulkiness and solvation of the entering ligands reflect in their properties as nucleophiles. Large negative values of the entropy of activation (ΔS≠), between ?140 and ?190 J K^?1 mol^?1, indicate that all thiols and thioethers react via the same associative mechanism. Results have been analyzed in relation to the antitumor activity and toxicity of platinum(II) complexes.     

Does deprotonated benzoic acid lose carbon monoxide in collision-induced dissociation?

Decarboxylation is known to be the major fragmentation pathway for the deprotonated carboxylic acids in collision-induced dissociation (CID). However, in the CID mass spectrum of deprotonated benzoic acid (m/z 121) recorded on a Q-orbitrap mass spectrometer, the dominant peak was found to be m/z 93 instead of the anticipated m/z 77. Based on theoretical calculations, ¹⁸O-isotope labeling and MS³ experiments, we demonstrated that the fragmentation of benzoate anion begins with decarboxylation, but the initial phenide anion (m/z 77) can react with trace O₂ in the mass analyzer to produce phenolate anion (m/z 93) and other oxygen-containing ions. Thus oxygen adducts should be considered when annotating the MS/MS spectra of benzoic acids.     

Polyaniline doped by a new class of dopants,benzoic acid and substituted benzoic acid: synthesis and characterization

This work reports on a new class of dopants, benzoic acid and substituted benzoic acids such as 2‐hydroxybenzoic acid, 2‐chlorobenzoic acid, 4‐nitrobenzoic acid, 2‐methoxybenzoic acid, 3‐methylbenzoic acid, 4‐methylbenzoic acid, 3‐aminobenzoic acid and 4‐aminobenzoic acid, for polyaniline. Benzoic acids can be used to dope polyaniline by mixing benzoic acid (or a substituted benzoic acid) with polyaniline in the common solvent 1‐methyl‐2‐pyrrolidone. Properties of benzoic acid doped polyaniline salts are studied using Fourier transform infra‐red, X‐ray diffraction spectroscopy, scanning electron microscopy, thermogravimetric analysis and conductivity measurements. The conductivity of polyaniline‐benzoic acid salt was found to be high (10⁻² S/cm) when compared to polyaniline‐substituted benzoic acid salts (10⁻³–10⁻⁵ S/cm). Copyright © 2005 John Wiley & Sons, Ltd.     

The mechanism of the sonochemical degradation of benzoic acid in aqueous solutions

The sonolytic degradation of benzoic acid in aqueous solution was investigated at an ultrasonic frequency of 355 kHz. The degradation rate was found to be dependent upon the solution pH and the surface activity of the solute. The degradation rate was favoured at a solution pH lower than the pK _a of benzoic acid. At pH < pK _a, HPLC, GC and ESMS analysis showed that benzoic acid could be degraded both inside the bubble by pyrolysis and at the bubble/solution interface by the reaction with OH radicals. At higher pH (> pK _a) benzoic acid could only react with OH radicals in the bulk solution. During the sonolytic degradation of benzoic acid, mono-hydroxy substituted intermediates were observed as initial products. Further OH radical attack on the mono-hydroxy intermediates led to the formation of di-hydroxy derivatives. Continuous hydroxylation of the intermediates led to ring opening followed by complete mineralization. Mineralization of benzoic acid occurred at a rate of < 40μM/h.     

FURTHER STUDIES ON THE KINETICS AND MECHANISM OF THE COPPER-IMIDAZOLE CATALYSED DECOMPOSITION OF HYDROGEN PEROXIDE

Abstract

The catalytic decomposition of hydrogen peroxide in the presence of the tetrakis(imidazole)copper(II) complex was investigated. The kinetics, based on the rates of oxygen evolution, indicated that a ternary copper(I1)-imidazole-peroxo complex is involved in the rate-determining step. The equilibrium constant for the coordination of hydrogen peroxide to the cupric ion, and the acid dissociation constant for the coordinated H202 ligand were calculated as 1.7 M¹ and 2.1 × 10⁹ M, respectively. The ternary complex undergoes intramolecular electron transfer, with k = 4 s¹, generating Cu(1) species which can react with hydrogen peroxide or dioxygen, returning to the catalytic cycle. A complete mechanism is proposed, based on the kinetics of oxygen and on the electrocatalytic behdviour observed for the copperimidazole complexes under a dioxygen atmosphere.     

Über Reaktionen von Alkylbiguaniden mit Benzoin beimpH der Biguanidbasen

Summary Alkylbiguanides2 a–e react with benzoin (1) at thepH of the base in different ways.1 undergoes in presence of2 a, c oxidation to benzoic acid which reacts with the bases2 a, c to yield 4-phenyl-1,3,5-triazinamines3 c, 4 c; in presence of2 b 1 is transformed to benzil, which reacts with2 b under rearrangement to yield 1-(4-oxo-5,5-diphenyl-2-imidazolin-2-yl)-3,3-dimethylguanidine (5 b). However, the cycloalkylbiguanides2 d, e, react in presence of nitrogen as well as oxygen with1 to yield piperidine-1-[N-(4,5-diphenylimidazol-2-yl)-carboxamidine] (7 d), resp. morpholine-4-[N-(4,5-diphenylimidazol-2-yl)-carboxamidine] (7 e). The structure of7 e was established by means of an X-ray structure analysis. All proton- and carbon resonances were assigned on the basis of 2-dimensional NMR data.

     

THE REACTIONS OF SOME 2-NITROPHENYL SULPHIDES IN 98% SULPHURIC ACID

Abstract

The coloured solutions of 2-nitrobenzenesulphenyl derivatives in 98% sulphuric acid have previously been suggested to contain either the conjugate acid of the sulphenyl derivative¹ or the sulphenium ion in equilibrium with the starting material. ¹⁹F n.m.r. studies on solutions of 4-trifluoromethyl-2-nitrobenzenesulphenyl derivatives show that these compounds react in sulphuric acid to give the corresponding 2-amino- and 2-nitro-benzenesulphonic acids together with other products.     

Über Reaktionen von Arylbiguaniden mit Benzoin beimpH der Biguanidbasen

Summary Arylbiguanides2 a–e react with benzoin (1) at thepH of the base to two different products.1 undergoes in presence of the base2 a–e oxidation to benzil and benzoic acid, which reacts fast with the arylbiguanides2 a–e to yield N-[4-(arylamino)-6-phenyl-1,3,5-triazine-2-yl]benzamides3 a–d. After lowering thepH of the reaction mixture, the bases2 b–e react with benzil to yield 2-[1-aryl-5-oxo-4,4-diphenyl-2-imidazoline-2-yl]guanidine4 b–e. The mechanism of the formation is discussed. The structure of4b was established from a single crystal x-ray structure analysis. The analysis was carried out at 100K: C₂₃H₂₁N₅O,M _r=383.5, monoclinic, C 2/c,a=15.842(6),b=8.419(3),c=30.223(10) Å, =98.44(3)°,V=3 987.3(9) ų,Z=8,d _x=1.277 g/cm³, =0.81 cm^–1,R=5.89%R _w=4.97% (1 537 observations, 233 parameters).

     

SYNTHESIS AND REACTVITY OF N-[N-PHOSPHORAMIDO-1H-BENZIMIDAZOL-2-YL] IMIDATES

N-(-1H-Benzimidazol-2-yl) imidates 1a–c react with chlorophosphoramide to give the N-[-1-N,N,N′,N′-tetramethylphosphoramidoyl-1H-benzimidazol-2-yl]-imidates 2a–c or with dichlorophosphoramide to yield the bis[(N-1-benzimidazol-2-yl)-imidate] phosphoramide derivatives 3a–b. The reaction of compounds 2a–c toward primary amines is studied. The obtained amidine derivatives 4a–b were unambiguously characterized by different spectroscopic techniques (IR, ¹H, ¹³C, and ³¹P NMR, and in some cases MS).     

4-溴-2-环戊烯砜酯化衍生物的合成

以3,4-二溴环戊砜(1)为原料, 在无水吡啶作用下发生消除反应, 得到反应中间体4-溴-2-环戊烯砜(2), 再分别与一系列取代苯甲酸盐3a～3c以及茜素黄GG (3d)发生酯化反应, 合成出4种新环戊烯砜衍生物4a～4d, 并用IR, ¹H NMR, MS, 元素分析等表征了它们的结构.     

The synthesis,structure, and magnetic studies of one supramolecular PtS net

A new 2-D coordination polymer, Co(H₂O)₂(Hoba)₂ (1) [H₂oba?=?4,4′-oxybis(benzoic acid)], was synthesized under hydrothermal conditions. Polymer 1 has been characterized by single-crystal X-ray diffraction and TG analysis. Through hydrogen bonds 1 shows a supramolecular four-connecting 3-D matrix with 4²8⁴ PtS topology. Magnetic studies reveal antiferromagnetic interactions.     

Microwave-assisted synthesis,characterization, and antimicrobial activity of some odorant Schiff bases derived from naturally occurring carbonyl compounds and anthranilic acid

Nine odorant Schiff bases, namely 2-(4-methoxybenzylideneamino) benzoic acid, 2-(benzylideneamino) benzoic acid, 2-(3-phenylallylidene amino) benzoic acid, 2-(3,7-dimethyloct-2,6-enylideneamino) benzoic acid, 2-(3,7-dimethyloct-6-enylideneamino) benzoic acid, 2-(4-isopropylbenzylideneamino)benzoic acid, 2-(3,4-dimethoxybenzylideneamino) benzoic acid, 2-(1-phenylethylideneamino) benzoic acid, and 2-[(4-(2,6,6-trimethylcyclohex-2-enyl)-but-2-enylideneamino)benzoic acid, were prepared by condensation of anthranilic acid with corresponding naturally occurring carbonyl compounds (anisaldehyde, benzaldehyde, cinnamaldehyde, citral, citronellal, cuminaldehyde, veratraldehyde, acetophenone, and α-ionone) employing conventional and microwave irradiation methods. These compounds were characterized with the aid of elemental and spectral (FT-IR, ¹H NMR, and ¹³C NMR) analysis. Microwave irradiation method was efficient in terms of reduced reaction time, solvent use, and increased yields of these compounds without affecting their olfactory characteristics. These Schiff bases also exhibited olfactory characteristics for various fragrance compositions and varied antimicrobial activity against Aspergillus niger, Penicillium chrysogenum, Staphylococcus aureus, and Escherichia coli.     

DFT study of the structure of hydroxybenzoic acids and their reactions with OH and radicals

B3LYP/6-31++G(d) method was used for the structural study of 3,4,5-trihydroxybenzoic acid (3,4,5-THBA), 3,4-dihydroxybenzoic acid (3,4-DHBA), and 4-hydroxybenzoic acid (4-HBA). Calculated structures agree with available X-ray experimental data within 2%. The phenolic OH bond dissociation enthalpy (BDE) of all sites in each benzoic acid were determined and compared with those of phenol (for 4-HBA) and catechol (for 3,4-DHBA). The consistency between the calculated values and experimental ones are within 5.4% and 9.2%, respectively, for 4-HBA and 3,4-DHBA. The reactions of benzoic acids with and OH radicals were studied and it turns out that benzoic acids react differently with both radicals. We have shown that the reaction of hydroxybenzoic acids with the hydroxyl radical was governed by a phenolic hydrogen (H⁺ + e⁻) transfer from the acid to the radical, while for the superoxide radical, the reaction is governed by a proton (H⁺) transfer from the acid to the radical. The first reaction is evidenced by the delocalization of the radical on the entire quinone moiety, and the second reaction is evidenced by the negative NBO charge on the phenoxide moiety as well as the localization of the radical on the hydroperoxy (O₂H) moiety.     

Synthesis of polyesters as binders for deinkable inks. I. Structural analysis of the polyesterification between o-phthalic anhydride and neopentyl glycol in bulk at 200°C by high resolution 13C nuclear magnetic resonance (13C-NMR)

Analysis of the polyesterification in bulk without any external catalyst at 200°C of o-phthalic anhydride with neopentyl glycol (2,2-dimethyl-1,3-propanediol) with a mole ratio ([(SINGLE BOND) COOH]/[ (SINGLE BOND) OH]) = 0.7 has been carried out by high resolution ¹³C nuclear magnetic resonance (¹³C-NMR). Polyesters can be analyzed by ¹³C-NMR spectra because of the fact that both o-phthalic acid (o-phthalic anhydride) and neopentyl glycol carbons are sensitive to sequence effects. Spin-lattice relaxation times T₁, of quaternary, tertiary and secondary carbons in different structures are in the 0.1–6.5 s range depending on the neighboring residue effects in the polymer chain. © 1996 John Wiley & Sons, Inc.     

Interfacial Behavior of Naphthenic Acids and Multivalent Cations in Systems with Oil and Water. I. A Pendant Drop Study of Interactions Between n‐Dodecyl Benzoic Acid and Divalent Cations

Abstract

Dynamic interfacial tension (IFT) measurements were used to investigate the interactions between a dissociated model naphthenic acid (p‐(n‐dodecyl) benzoic acid) and various divalent metallic cations (Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺) across a toluene/hexadecane–water interface. The measurements were performed by using the pendant drop technique. The results obtained, plotted as IFT vs. time gave curves with similar shapes but different slopes and levels of the equilibrium IFT, depending upon the acid and salt concentrations and the type of cation added. Due to differences in degree of hydration of the various cations, the products of the reaction between dissociated acid monomers and the cations showed differences in solubility, which, in turn, affected the IFT. Based on the shapes of the curves, the mechanisms of the reactions involved in the process are discussed.