Synthesis and characterization of isotopically enriched methylmercury (CH3201Hg+)

A simple procedure for the synthesis of an important standard, isotopically enriched methylmercury, which is not commercially available, has been established successfully. The isotopically enriched standard synthesized is utilized in conventional isotope dilution mass spectrometry (IDMS), as well as in speciated IDMS (SIDMS), for determination of the true concentration of methylmercury in environmental samples. The CH₃²⁰¹Hg⁺ standard has been synthesized from commercially available ²⁰¹HgO and tetramethyltin. The synthesis time required is 1 h at 60°C. The product is highly pure, yielding more than 90% as ²⁰¹Hg in CH₃²⁰¹Hg⁺. Hazardous dimethylmercury does not occur during this synthesis procedure. The product synthesized was analyzed using high‐performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (ICP‐MS) and ICP‐MS alone in order to determine its concentration, isotopic composition and purity. The stability of the product was also evaluated for over 6 months and found to be stable at 4°C in the dark. The isotopically enriched methylmercury synthesized can be used in SIDMS and IDMS analyses as a standard. Copyright © 2003 John Wiley & Sons, Ltd.     

Nitroxide‐mediated radical polymerization in miniemulsion: Bimolecular termination in monomer‐free model systems

Bimolecular termination in nitroxide‐mediated radical polymerization in miniemulsion has been investigated through the heating of a polystyrene–2,2,6,6‐tetramethylpiperidinyl‐1‐oxy macroinitiator and its 4‐hydroxy‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy analogue in an aqueous toluene dispersion with sodium dodecyl benzenesulfonate as a surfactant at 125 °C. The level of bimolecular termination by combination, evaluated from the high‐molecular‐weight shoulder, was higher in miniemulsion than in solution and increased with decreasing particle size. Quantitative analysis revealed that these results cannot be rationalized solely by nitroxide partitioning to the aqueous phase. The results are explained by an interface effect, by which nitroxide is adsorbed or located at the aqueous–organic interface. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4995–5004, 2007     

Novel route to synthesis of allyl starch and biodegradable hydrogel by copolymerizing allyl‐modified starch with methacrylic acid and acrylamide

Maize starch was modified by allyl chloride adopting an interfacial reaction technique with cetyltrimethyl ammonium bromide as a phase‐transfer catalyst and pyridine as an acid acceptor. The degree of substitution was determined from an increasing carbon content of the modified starch. The percentage of carbon and hydrogen of the allyl‐modified starch was estimated by elemental analysis (C, H, and N), and the product characterization was done through ¹H NMR and ¹³C NMR analyses. The allyl‐modified starch was then copolymerized with methacrylic acid and a combination of methacrylic acid and acrylamide at 50 and 70 °C with potassium persulfate as an initiator. The copolymer thus formed swelled in distilled water after neutralization with sodium carbonate. The percentage of absorption capacity of the hydrogels was determined with distilled water and 0.9% NaCl solution. The highest percentage of absorption, 6500%, was achieved for the developed hydrogel containing allyl starch and acrylic monomer in a 1.7:1 w/w ratio and acrylic monomer, namely, methacrylic acid and acrylamide in a 3.2:1 w/w ratio. The study on biodegradability of the developed hydrogel showed that the hydrogel is degradable in the presence of diastase (amylase). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1650–1658, 2003     

A simple convenient synthesis of trans-1,2,3,4,4a,5,6,10b-octahydrophenanthridines

trans-1,2,3,4,4a,5,6,10b-Octahydrophenanthridine, the 9-methoxy analog, and 5-methyl derivatives ( 6a,6b ) of each have been synthesized from trans-phenylcyclohexylamines ( 2a,2b ) and ethyl chloroformate followed by cyclization and reduction or by cyclization, N-methylation and reduction. The oximes ( la,1b ) of 2-phenylcyclohexanone and the m-methoxy relative, a mixture of the syn and anti isomers, were reduced to 2a and 2b with sodium and ethanol. Hydrogenation (platinum oxide-acetic acid) of 1a gave in addition to 2a , a small yield of 2-cyclohexylcyclohexyl-amine. Similar hydrogenation of 1b gave only this fully reduced compound.     

Preparation,and infrared and thermal properties of six adducts of tetrakis-(8-hydroxyquinolinato)thorium(IV)

Six adducts of the tctrakis(8-hydroxyquinolinato) complex of thorium(IV) with 8-hydroxyquinoline, pyridine, urea, dimethylsulphoxide, dimethylformamide and 1,10-phenanthroline were prepared and characterized, the infrared bands for the room-temperature forms are given and their particular thermal properties are reported. The thermal analyses were performed mostly in the presence of air, but in some cases an argon atmosphere was used for comparison. The adducts were lost from the principal complex at temperatures varying between 110 and 290°. Intermediate oxygenated complexes were formed in each case at about 400°. The thermal data suggest the standardization of a procedure for the formation of Th(C₉H₆NO)₄.

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Zusammenfassung Sechs Addukte des Tetrakis(8-hydroxyquinolinato)-Komplexes von Thorium(IV) mit 8-Hydroxyquinolin, Pyridin, Harnstoff, Dimethylsulphoxid, Dimethylformamid und 1,10-Phenanthrolin wurden dargestellt und charakterisiert. Infrarotbanden und spezielle thermische Eigenschaften der Raumtemperatur-Formen sind angegeben. Die thermischen Analysen wurden meist in Luft ausgeführt, in einigen Fällen zu Vergleichszwecken aber auch in Argonatmosphäre. Die Addukte wurden vom Komplex bei Temperaturen zwischen 110 und 290 °C abgegeben. Intermediäre oxydierte Komplexe wurden in jedem Fall bei etwa 400 °C gebildet. Die thermischen Daten ermöglichen die Standardisierung eines Verfahrens zur Darstellung von Th(C₉H₆NO)₄.

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-(8- ) (IV) 8- , , , - , 1,10-. - , . , , . 110–290°. 400° . Th(C₉H₆NO)₄.

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We are grateful to the Bangladesh University Grants Commission for a Fellowship Grant to AR.     

The preparation and some reactions of 2, 3, 5, 6-tetrachlorophenylmagnesium chloride

The reaction of pentachlorobenzene with metallic magnesium in THF at 10–15°C gives after hydrolysis 1, 2, 4, 5-tetrachlorobenzene (76%) and pentachlorobenzene (8%); after trimethylsilylation, 1, 2, 4, 5-tetrachloro-3-(trimethylsilyl)benzene (74%), pentachloro(trimethylsilyl)benzene (8%) and 1, 2, 4, 5-tetrachlorobenzene (6%); after iodination, 1, 2, 4, 5-tetrachloroiodobenzene (44%), pentachloroiodobenzene (12%) and 1, 2, 4, 5-tetrachlorobenzene (9%); and finally after carbonation, 2, 3, 5, 6-tetrachlorobenzoic acid (58%). These products indicate that in the Grignard reaction a mixture of largely 2, 3, 5, 6-tetrachlorophenylmagnesium chloride and some pentachlorophenylmagnesium chloride is formed. The formation pentachlorophenylmagnesium chloride is explained on the basis of metal—hydrogen exchange reaction between 2, 3, 5, 6-tetrachlorophenylmagnesium chloride and the unreacted pentachlorobenzene.     

Production of indigotin in submerged culture using morchella nov. ES-1

A new strain of the fungusMorchella nov. ES-1 (ATCC 20951) that produces blue pigment in submerged culture has been isolated. The blue pigment was extracted by chloroform or ethyl acetate treatment. The crude extract when chromatographed yielded three fractions; a blue one has been identified by mass spectrometry as indigotin. Fermentation studies using enriched media revealed that maximum accumulation of indigotin in culture was approx 24 mg/L in 168 h.     

Spectrophotometric determination of trimethoprim by oxidation in drug formulations

A spectrophotometric determination of trimethoprim is described based on the reaction of its amine group with persulfate which acts as a strong oxidizing agent in alkaline media. The reaction produces a stable yellow colored compound after heating in a boiling water bath for 30 min. At λ_max 355 nm, Beer’s law is obeyed in the concentration range 10–60 μg ml^–1 with a molar absorptivity of 2.7 × 10³ l mol^–1cm^–1. The method is applied to formulations with sulfamethoxazole. Received: 30 July 1996 / Revised: 16 October 1996 / Accepted: 22 October 1996     

Chemical and Pharmacological Profiling of Wrightia coccinea (Roxb. Ex Hornem.) Sims Focusing Antioxidant,Cytotoxic, Antidiarrheal,Hypoglycemic, and Analgesic Properties

The aim of the study was to conduct phytochemical and pharmacological investigations of Wrightia coccinea (Roxb. ex Hornem.) Sims via several in vitro, in vivo, and in silico models. A total of four compounds were identified and isolated from the methanol extract of the bark and the methanol extract of the seed pulp of W. coccinea through successive chromatographic techniques and were characterized as 3β-acetyloxy-olean-12-en-28-ol (1), wrightiadione (2), 22β-hydroxylupeol (3), and β-sitosterol (4) by spectroscopic analysis. The aqueous fraction of the bark and chloroform fraction of the fruits provided the most potent antioxidant capacity (IC₅₀ = 7.22 and 4.5 µg/mL, respectively) in DPPH free radical scavenging assay compared with the standard ascorbic acid (IC₅₀ = 17.45 µg/mL). The methanol bark extract and the methanol fruit coat extract exerted anti-diarrheal activity by inhibiting 74.55 ± 0.67% and 77.78 ± 1.5% (mean ± SEM) of the diarrheal episode in mice, respectively, after four hours of loading the samples. In the hypoglycemic test, the methanol bark extract and the methanol fruit coat extract (400 mg/kg) produced a significant (p < 0.05) reduction in the blood glucose level in mice. Both doses of the plant extracts (200 mg/kg and 400 mg/kg) used in the study induced a significant (p < 0.05) increase in pain reaction time. The in vitro and in vivo findings were supported by the computational studies. The isolated compounds exhibited higher binding affinity compared with the standard drugs towards the active binding sites of glutathione reductase, epidermal growth factor receptor (EGFR), kappa opioid receptor, glucose transporter 3 (GLUT 3), Mu opioid receptor, and cyclooxygenase 2 (COX-2) proteins due to their potent antioxidant, cytotoxic, anti-diarrheal, hypoglycemic, and central and peripheral analgesic properties, respectively. The current findings concluded that W. coccinea might be a potential natural source for managing oxidative stress, diarrhea, hyperglycemia, and pain. Further studies are warranted for extensively phytochemical screening and establishing exact mechanisms of action.