The Kinetics of Tenoxicam Photodegradation in Solution

Photodegradation of tenoxicam was investigated under different reaction conditions. After 60 min of exposure to UV light, the photodegradation was extensive, and the maximum and minimum in the UV-visible spectrum were shifted to shorter and longer wavelengths, respectively. Ethanol exerted a photostabilizing effect on tenoxicam. Tenoxicam is more stable in acidic and basic media than in neutral solution. Increasing light intensity or temperature causes an increase in the rate of photodegradation. The photodegradation of tenoxicam was found to follow first-order kinetics under all these conditions.     

The gas-phase on-line production of vanadium oxytrihalides, VOX3 and their identification by infrared spectroscopy

A new route has been devised, leading to the production of VOX₃ molecules where X=F, Br and I by an on-line process using vanadium oxytrichloride, VOCl₃ as a starting compound passed over the following heated salts NaF, KBr and KI at 375, 700 and 550°C, respectively. The products have been characterized by the IR spectra of their vapors. The low resolution gas phase on-line Fourier transform infrared spectra reported for the first time show strong bands with PQR type structure, centered at 1058, 1035, 1030 and 1025 cm⁻¹ assigned to the ν₁(a₁), the O=V stretching fundamental mode of VOF₃, VOCl₃, VOBr₃ and VOI₃, respectively.     

Influence of Process Parameters on the Reaction Kinetics of the Chromium‐Catalyzed Trimerization of Ethylene

In this paper we report the results of an extensive experimental kinetic study carried out on the novel ethylene trimerization catalyst system, comprising the chromium source [CrCl₃(thf)₃] (thf=tetrahydrofuran), a Ph₂P‐N(iPr)‐P(Ph)‐N(iPr)H (PNPNH) ligand (Ph=phenyl, iPr=isopropyl), and triethylaluminum (AlEt₃) as activator. It could be shown that the initial activity shows a first‐order dependency on the ethylene concentration. Also, a first‐order dependency was found for the catalyst concentration. The initial activity follows a typical Arrhenius behavior with an experimentally determined activation energy of 52.6 kJ mol^?1. At elevated temperatures (ca. 80 °C), a significant deactivation was observed, which can be tentatively traced back to a ligand rearrangement in the presence of AlEt₃. After a fast initial phase, a pronounced ‘kink’ in the ethylene‐uptake curve is observed, followed by a slow, almost linear, further increase of the total ethylene consumption. The catalyst composition, in particular the ligand/chromium and the cocatalyst/chromium molar ratio, has a strong impact on the catalytic performance of the trimerization of ethylene.     

Effect of tri-potassium phosphate on volumetric,acoustic, and transport behaviour of aqueous solutions of 1-ethyl-3-methylimidazolium bromide at T = (298.15 to 318.15) K

Density, sound velocity, and viscosity of 1-ethyl-3-methylimidazolium bromide, [Emim][Br], in aqueous solutions of tri-potassium phosphate with salt weight fractions (w_s = 0.00, 0.10, 0.15, and 0.20) have been measured as a function of concentration of [Emim][Br] at atmospheric pressure and T = (298.15, 303.15, 308.15, 313.15, and 318.15) K. The apparent molar volume, isentropic compressibility, apparent isentropic compressibility, and relative viscosity values have been evaluated from the experimental data. The partial molar volume and isentropic compressibility at infinite dilution, and viscosity B-coefficient obtained from these data have been used to calculate the corresponding transfer parameters for the studied IL from water to the aqueous tri-potassium phosphate solutions. Also, an empirical equation was satisfactorily used to correlate the experimental viscosity data.     

Quantitation of transdermal tadalafil in human skin by reversed-phase high-performance liquid chromatography

A reliable and sensitive HPLC method was developed for the quantitation of tadalafil transdermal permeation through human skin. An RP column with UV detection at 290 nm was used for chromatographic separation at ambient temperature. The mobile phase was acetonitrile-water containing 20 mM pH 7 phosphate buffer (35/65, v/v) with a flow rate of 1.0 mL/min. The LOQ achieved was 1 ng/mL, and the calibration curve showed good linearity over the concentration range of 5-2000 ng/mL for tadalafil, with a determination coefficient (R2) of 0.998. The RSD values of intraday and interday analyses were all within 7%. Parameters of validation proved the precision of the method; this validated method was applied for the determination of tadalafil in transdermal permeation and drug deposition in human skin studies.     

The role of C-H and C-C stretching modes in the intrinsic non-radiative decay of triplet states in a Pt-containing conjugated phenylene ethynylene

The intrinsic non-radiative decay (internal conversion) from the triplet excited state in phosphorescent dyes can be described by a multi-phonon emission process. Since non-radiative decay of triplet excitons can be a significant process in organic light-emitting diodes, a detailed understanding of this decay mechanism is important if the overall device efficiency is to be controlled. We compare a deuterated Pt(II)-containing phenylene ethynylene with its non-deuterated counterpart in order to investigate which phonon modes control to the non-radiative decay path. We observe that deuteration does not decrease the non-radiative decay rate. A Franck-Condon analysis of the phosphorescence spectra shows that the electronic excitation is coupled strongly to the breathing mode of the phenyl ring and the C≡C carbon stretching modes, while high-energy C-H or C-D stretching modes play an insignificant role. We, therefore, associate the internal conversion process with the carbon-carbon stretching vibrations.     

Synthesis and characterization of thiolate-Ag(I) complexes by solid-state and solution NMR and their antimicrobial activity

Silver(I) complexes of several thiolates have been prepared. These complexes have been characterized by elemental analysis and 13C NMR spectroscopy. All the Ag(I)-thiolate complexes are polymeric in nature. Therefore, 13C CP MAS NMR is being used extensively to analyze the binding site of the ligand and the nature of complexation. A significant shift difference was observed for S binding site whereas smaller shift was observed for carboxylate binding site. The antimicrobial activities for Ag(I)-glutathione complex was measured and compared with Ag(I)-captopril complex.     

Efficient Synthesis of New 2H‐Chromene Retinoids Hybrid Derivatives by Suzuki Cross‐coupling Reactions

In an attempt to improve anticancer activity, a series of retinoids–chromene hybrids was described. The novel heterocyclic chromene–retinoids hybrid including oxygen as a heteroatom in a six‐membered cyclic ring (2H‐chromene or 2H‐1‐benzopyran) was designed and synthesized by introducing different groups such as an aromatic or styrylphenyl ring in 6‐position of 2H‐chromene. These novel compounds were synthesized by using the efficient cascades one‐pot process involving Wittig–Horner–Emmons reaction and Suzuki–Miyaura cross‐coupling pallado‐catalyzed reactions with 60% to 90% overall yields. These new compounds were tested against glioblastoma multiforme brain cancer, medulloblastoma, neuroblastoma cell lines, and breast cancer MCF‐7 cell lines. Two of them exhibited an appreciable anti‐tumor activity in the low micromolar range, which opens new perspectives for therapeutic application on humans.     

Design and synthesis of new series of 3-cyanopyridine and pyrazolopyridine derivatives

Reaction of 3-cyano-4,6-dimethyl-2-pyridone with ethyl chloroacetate afforded ethyl 2-([3-cyano-4,6-dimethylpyridin-2-yl]oxy)acetate 2 and ethyl 2-(3-cyano-4,6-dimethyl-2-oxopyridin-1[2H]-yl)acetate 3 , the reaction product yield depend on the reaction condition (potassium carbonate concentration and reaction time). These compounds used as precursors to synthesize pyridine derivatives 4 , 6-10 , 15, 17-20 , furopyridines 5, 16 , pyrazolopyridine 12 , pyridopyrazolopyrimidines 14a,b . The structure of the newly synthesized compounds was confirmed by spectral data (IR, NMR, and mass spectra) and elemental analysis.     

Reassignment of the structures of products produced by reactions of the product believed to be 2-(1-phenyl-2-thiocyanatoethylidene)-malononitrile with electrophiles

The reactivity of the product believed to be 2-(1-phenyl-2-thiocyanato-ethylidene)malononitrile toward a variety of electrophilic and nucleophilic reagents is reported.