STM/AFM studies of the evolution of morphology of electroplated Ni/W alloys

The surface morphology evolution of Ni/W alloys was studied, as a function of the alloy composition. Using the modified plating baths developed in our laboratory recently, electroplated Ni/W alloys with different W content, in the range of 7–67 atom percent (a/o), can be obtained. This was found to lead to different structures, ranging from polycrystalline fcc-Ni type structure to amorphous, followed by orthorhombic with increasing W content in the alloy. Powder XRD was studied to determine the crystal structures. Ex situ STM, AFM and SEM were used to study in detail the surface morphologies of the different alloys, and their evolution with increasing W content.

The important findings are that a mixture of two crystalline forms can give rise to an amorphous structure. Hillocks that are usually a characteristic of epitaxial growth can also exist in the amorphous alloys. Oriented scratches caused by stress can also be formed.

Up to 20 a/o of W is deposited in the alloys in crystalline form, with the fcc-Ni type structure. Between 20 and about 40 a/o an amorphous structure is observed, and above that an orthorhombic crystal structure is seen, which is characteristic of the NiW binary alloy. Careful choice of the composition of the plating bath allowed us to deposit an alloy containing 67 a/o W, which corresponds to the composition NiW₂.     

MgBr2·OEt2 mediated protection of alcohols with hexamethyldisilazane: An efficient catalytic route for the preparation of silyl ethers under solvent-free conditions

Various types of alcohols and phenols were rapidly protected by hexamethyldisilazane in good to excellent yields at room temperature in the presence of catalytic amount of magnesium bromide ethyl etherate under solvent-free conditions. Good to excellent chemoselectivity was demonstrated for competitive protection of primary hydroxyls in the presence of secondary and tertiary alcohols. Highly selective protection of phenols in the presence of aromatic amines was also demonstrated successfully.     

Modified determination of dihydrostreptomycin in kidney, muscle and milk by HPLC.

A method is presented for the determination of dihydrostreptomycin in milk, muscle and kidney by reversed-phase ion-pair high-performance liquid chromatography and post-column derivatisation with beta-naphthoquinone-4-sulfonate prior to fluorescence detection. The new sample work-up procedures include acid precipitation of proteins and, in the case of muscle and kidney, removal of fats by solvent extraction followed by solid phase extraction on a cation exchanger. The fluorescence response was linear from 25 to 2000 micrograms l-1 of injected analyte. The detection limits were 10 micrograms kg-1 for milk and 15 micrograms kg-1 for muscle and kidney and the analyte recoveries were on average 93% for milk, 70% for kidney and 75% for muscle.     

Stereochemistry of new nitrogen containing heterocyclic aldehyde. VII. Potentiometric, conductometric and thermodynamic studies of novel quinoline azodyes and their metal complexes with some transition metals

A novel series of quinoline azodyes (5-(4'-derivatives phenyldiazo)-8-hydroxy-7-quinolinecarboxaldehyde)) (HL1-HL5) has been prepared and characterized by elemental analyses, 1H-NMR and IR spectra. The IR spectral data indicate that the compounds can exist in two resonance structures. Proton-ligand dissociation constants of quinoline azodyes and their subsituted derivatives, and metal-ligand stability constants of their complexes with bivalent (Mn2+, Co2+, Ni2+, Cu2+) metal ions have been determined potentiometrically in 0.1 m KCl and 40% (v/v) dimethylformamide (DMF)-water mixture. The influence of substituents on the dissociation and stability constants was examined on the basis of the electron repelling property of the substituent. The order of the stability constants of the formed complexes was found to be Mn2+ < Co2+ < Ni2+ < Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (deltaG, deltaH, deltaS) were derived and discussed. The stoichiometries of these complexes were determined conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes was indicated.     

Three new cholinesterase-inhibiting cis-clerodane diterpenoids from Otostegia limbata

Three new tricyclic cis-clerodane type diterpenoids trivially named as limbatolide A (1), limbatolide B (2) and limbatolide C (3) have been isolated from the roots of Otostegia limbata along with two known compounds; oleanic acid and beta-sitosterol. The structure elucidation of the new compounds was based primarily on two-dimensional (2D) NMR techniques. Compounds 1-3 displayed inhibitory potential in a concentration-dependent manner against acetylcholinesterase (AChE; EC 3.1.1.7) and butyrylcholinesterase (BChE; EC 3.1.1.8) enzymes, respectively.     

Spectral Studies on Some Pyrimidine Derivatives in Different Solvents

The electronic absorption spectra of 2-aminopyrimidine (compound I), 2-amino-4-methylpyrimidine (compound II), 2-amino-4,6-dimethylpyrimidine (compound III), 2-amino-4,6-dimethoxypyrimidine (compound IV), 4-amino-2,6-dimethylpyrimidine (compound V), and 4,5-diamopyrimidine (compound VI) have been measured in water and in a series of different organic solvents. The solvent effects on the spectra are discussed and the solvent induced spectral shifts are analyzed in terms of different solute–solvent interaction mechanisms, using the multiple linear regression technique.     

Structure determination of bioactive galloyl derivatives by NMR spectroscopy

The investigation of the chemical constituents of Symplocos racemosa Roxb led to the isolation of two new glycosides, symcomoside A (1) and symcomoside B (2), together with one known glycoside, tortoside C (3), which is reported for the first time from this plant. The structures of the new compounds were determined by 1D and 2D homonuclear and heteronuclear NMR spectroscopy, from chemical evidence and by comparison with published data for closely related compounds. Symcomoside B (2) showed potent inhibitory activity against alpha-glucosidase in a concentration-dependent fashion with an IC50 value of 0.733 +/- 0.033 mM whereas symcomoside A (1) showed very weak inhibitory activity against alpha-glucosidase (9.90% in 0.70 mM).     

Base induced cyclization of some quinolines. Formation of fused nitrogen heterocyclic ring system

Condensation of 3,5-dinitro-4-chloro-6-methoxy-2-methylquinoline (1) with benzylamine, ethanolamine and/or thioglycolic acid afforded the quinoline derivatives4 a-c. Cyclization of4 a and4 b with alkali and condensation of1 with glycine in sodium carbonate solution furnish 2H-imidazo[4,5-c]quinoline derivatives5 a-c, respectively. Treatment of5 b with benzaldehyde in presence of zinc chloride gave the styryl derivative6. 1 reacted with sodium azide to give the azido derivative4 d, which upon treatment with phenylhydrazine or sodium borohydride yielded the 4-amino derivative4 3. Moreover,1 was treated with phenylhydrazine to give4 f, which cyclized in 10% sodium hydroxide solution to the corresponding v-triazolo[4,5-c]quinoline 3-oxide derivative7. When however4 f was treated with dilute hydrochloric acid, the corresponding phenylpyrazolo[3,4,5-de]quinoline derivative8 was obtained.

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Baseninduzierte Cyclisierung einiger Chinoline. Darstellung höherer Stickstoff-Heterocyclen

Zusammenfassung Kondensation von 3,5-Dinitro-4-chlor-6-methoxy-2-methylchinolin (1) mit Benzylamin, Ethanolamin und/oder Thioglycolsäure ergab die Chinolinderivate4 a-c. Cyclisierung von4 a und4 b mit Alkali und Kondensation von1 mit Glycin in Natriumcarbonatlösung lieferte 2H-imidazo[4,5-c]chinolin-Derivate5 a-c. Behandlung von5 b mit Benzaldehyd in Gegenwart von Zinkchlorid ergab das Styrylderivat6. 1 wurde mit Natriumazid zum Azidoderivat4 d umgesetzt, das mit Phenylhydrazin oder Natriumborhydrid zum 4-Aminoderivat4 e weiterreagierte.1 ergab mit Phenylhydrazin4 f, das in 10% NaOH-Lösung zum entsprechenden Triazolo[4,5-c]chinolin-Derivat7 cyclisierte. Aus4 f wurde mit verdünnter Salzsäure das Phenylpyrazolo[3,4,5-de]chinolin8 erhalten.

     

Simultaneous Spectrophotometric Determination of Group B Vitamins Using Parallel Factor Analysis: PARAFAC

In this work, a simple and rapid analytical procedure was applied for simultaneous determination of folic acid (vitamin B₀), thiamin (vitamin B₁), riboflavin (vitamin B₂) and pyridoxal (vitamin B₆) based on the absorbance data in the pH range 2.0‐12.0 at 25 °C using parallel factor analysis (PARAFAC). The effect of the pH as the most important factor on the sensitivity of the determination was studied. The spectral data were recorded in 400‐650 nm intervals and a 2‐12 pH range for all four vitamins. The calibration set was constructed in the concentration ranges of 4‐22, 1‐20, 6‐26, and 4‐20 μg mL^?;1 for B₆,B₂,B₁ and B₀, respectively. The root mean squares errors of prediction for the prediction set, (RMSEP), are 0.65, 0.63, 1.13 and 0.34 for B₀,B₁,B₂ and B₆, respectively. The recovery percent for the validation set are in the range of 90.6 to 107.0%. The effect of the experimental conditions and diverse species were discussed. The optimum values of these factors were searched according to the relative standard deviation of the prediction set of mixtures solutions.     

PHOTOCHEMISTRY OF ALL-TRANS- AND 13-CIS-14,15-DIDEUTERIORETINAL

Abstract— All- trans - and 13- cis -14,15-dideuterioretinal were synthesized and their solution photochemistry examined. Quantum yields of trans → cis or cis → trans photoisomerization and the number and ratio of primary photoproducts, determined by high pressure liquid chromatographic analysis, are essentially identical to that of their corresponding retinal isomer. The C-14, C-15 carbon-hydrogen modes play no particularly important role in the deactivation of electronically excited linear polyenes related to retinal.