Kinetics and mechanism of the oxidative decolorization of direct violet 31 in the presence of peroxodisulfate-silver(I) as a redox system

Transition Metal Chemistry - The redox decolorization of direct violet 31 [DV-31]? by Ag(I)/S2O82? under conditions similar to the Fenton process was studied kinetically in aqueous...     

Simultaneous determination of hyoscine butylbromide and ketoprofen in pharmaceutical preparations by spectrophotometric and liquid chromatographic methods

A binary mixture of hyoscine butylbromide and ketoprofen was determined by 4 different methods. The first involved determination of hyoscine butylbromide and ketoprofen using the ratio-spectra first-derivative spectrophotometric technique at 211 and 234 nm over the concentration ranges of 2-14 and 5-45 microg/mL with mean accuracies 99.84 +/-0.92 and 99.98+/- 0.64%, respectively. The second method utilized second-derivative spectrophotometry over the concentration ranges of 2-14 and 5-35 microg/mL with mean accuracies 99.32+/- 1.06 and 99.55+/-1.15%, respectively. The third method was based on the resolution of the 2 components by bivariate calibration depending on a simple and rapid mathematical algorithm and quantitative evaluation of the absorbances at 206 and 254 nm over concentration ranges of 2-16 and 5-35 microg/mL; mean accuracies of 100.21+/-1.30 and 100.19 +/-1.07% were obtained for hyoscine butylbromide and ketoprofen, respectively. The fourth method was reversed-phase liquid chromatography using 0.05 M ammonium dihydrogen phosphate-acetonitrile-methanol (20 + 30 + 6, v/v) as the mobile phase with ultraviolet detection at 220 nm over concentration ranges of 1-90 and 5-70 microg/mL; mean accuracies were 99.92+/-1.02 and 99.61+/- 0.98%, respectively. The suggested procedures were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical preparations. The methods retained their accuracy and precision when the standard addition technique was applied. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the manufacturer's method.     

Microwaves in organic synthesis: Facile synthesis of biologically active pyridazinone and iminopyridazine derivatives

Condensation of Wittig reagents 1a,b with arylhydrazones 2a,b by conventional and by microwave heating techniques furnished the corresponding pyridazines 3a‐e . The arylhydrazones 7a,b were allowed to react with 1a,b under the same conditions to produce the pyridazinones 10a,b and iminopyridazines 11a,b respectively. On the other hand, the arylhydrazones 12a‐c reacted with 1a to afford the pyridazinones 13a‐c . Treatment of 3b with dimethylformamide dimethyl acetal (DMFDMA) produced the adduct 15 . The utility of microwave heating technique led to the reduction of the reaction times to few minutes and to the improvement of the yields of the products. The in vitro biological activity of some newly prepared compounds against four types of fungi was studied.     

Synthesis of some novel 2,6‐disubstituted pyridazin‐3‐ones as TMC120 analogues

Different analogues of TMC120 derived from pyridazin‐3(2H)‐one rings were synthesized by coupling of 3,6‐dichloropyridazine with arylacetonitriles, phenols and/or aniline derivative followed by hydrolysis and alkylation with different benzyl bromide derivatives.     

1-Acyl-and 1,2-dihydro-1<Emphasis Type="Italic">H</Emphasis>(acyl)deoxyvasicinones. Synthesis and chemical transformations

1-Acyl-and 1,2-dihydro-1H(methyl, acyl)deoxyvasicinones were synthesized. Their PMR and ¹³C NMR spectra were investigated. The chemical shifts and SSCC were determined. 1-Acyl derivatives were produced by acylation of 1,2-dihydrodeoxyvascinone with caprylyl-and chloroacetylchlorides. It was shown that the Cl atom of 1-chloroacetyldeoxyvasicinone was labile and underwent nucleophilic substitution by amines. In contrast with this, it reacted with cyanide, hydroselenide, methoxide, phenoxide, and anions of compounds with an activated methylene group in a completely different direction to cleave the chloroacetyl group and form 1,2-dihydrodeoxyvasicinone. It was found that addition of 1,2-dihydrodeoxyvasicinone to phenylacetylene occurred regio-and stereoselectively to form the cis-isomer of 1-(2-phenylvinyl)-1,2-dihydrodeoxyvasicinone. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 353–359, July–August, 2007.     

Recapturing lost evanescent power by tuning end face total internal reflection capable tunneling modes at a roughened fiber end face

We reveal that the overall evanescent wave (EW) power captured by an unclad multimode fiber employed in a sensing configuration is determined by the tunneling modes, not the guided modes. While enormous in strength, most of this power is inaccessible using traditional EW power enhancers. However, we found that by roughening the fiber end face, this supposedly lost power can be recaptured and thus can boost the detectable power level significantly. Intensive mode mixing events across various mode categories are proposed to interpret the observed phenomenon.     

Synthesis and characterization of novel dipeptide ester prodrugs of acyclovir

Four dipeptide (Gly-Gly, Gly-Val, Val-Val, Val-Gly) ester prodrugs of 9-[(2-hydroxyethoxy)methyl]guanine (acyclovir, ACV) were synthesized. LC/MS was used to characterize the new prodrugs. Both 1H NMR and 13C NMR spectra of the four prodrugs of ACV were measured and assigned based on spectral comparison with compounds of similar structures.     

Assessment of health hazard due to natural radioactivity in Kluang District,Johor, Malaysia

The radiation survey of the ambient environment was conducted using two gamma detectors, and the measurement results were used in the computation of the mean external radiation dose rate, mean-weighted dose rate and annual effective dose, which are 144 nGy h^?1, 0.891 mSv y^?1 and 178 μSv, respectively. A high-purity germanium detector was used to determine the activity concentrations of ²³²Th, ²²⁶Ra and ⁴⁰K in soil samples. The results of the gamma spectrometry of the soil samples show radioactivity concentration ranges from 19±1 to 405±13 Bq kg^?1 with a mean value of 137±5 Bq kg^?1 for ²³²Th, from 21±2 to 268±9 Bq kg^?1with a mean value of 78±3 Bq kg^?1 for ²²⁶Ra and from 23±9 to 1268±58 Bq kg^?1 with a mean value of 207±13 Bq kg^?1 for ⁴⁰K. Radium equivalent activity (Ra_eq) and external hazard index (H_ex) were 290 Bq kg^?1 and 0.784, respectively, which were safe for the population. The mean lifetime dose and lifetime cancer risk for each person living in the area with average lifetime (70 y) were 12.46 mSv and 7.25×10^?4 Sv year, respectively. The results were compared with values given in United Nations Scientific Committee on the Effects of Atomic Radiation 2000.     

Polarographic behaviour of some organotin(IV) compounds in dimethyl sulphoxide

The differential pulse polarographic behaviour in dimethyl sulphoxide (DMSO) of 14 organotin(IV) compounds having the general formula R₃SnX (R = Me, Ph; X^? = NCS^?, N₃^?, N₃^?, NO₃^?, OH^?, NCO^? and OAc^?) and ⁿBu₃SnCl and ⁿBu₂SnCl₂ has been studied. The peak potential was found to depend markedly on the organic group and to a lesser extent on the nature of the anion X. The phenyltin compounds were reduced at lower potentials than the corresponding methyltin compounds. The data obtained could be used for trace determination of these compounds. Linear calibration curves were obtained over the concentration range of 2.8 × 10^?4 to 1.9 × 10^?6 mol dm^?3.