Showing papers by "Badiadka Narayana published in 2005"

Synthesis of some new 2-(6-methoxy-2-naphthyl)- 5-aryl-1,3,4-oxadiazoles as possible non-steroidal anti-inflammatory and analgesic agents.

Abstract: The synthesis of some new 2-(6-methoxy-2-naphthyl)-5-aryl-1,3,4-oxadiazoles (4a-k) has been described. Ethyl-6-methoxy-2-naphthoate (1) yielded on treatment with hydrazine hydrate to 6-methoxy-2-naphthoic acid hydrazide (2). Compound 2 reacted with substituted aromatic carboxylic acids (3a-k) in phosphorus oxychloride yielded 2-(6-methoxy-2-naphthyl)-5-aryl-1,3,4-oxadiazoles (4a-k). Newly synthesized compounds were characterized by IR, (1)H-NMR and mass spectral data. All the compounds were screened for their anti-inflammatory and analgesic activity. Compound 4j exhibited promising anti-inflammatory and analgesic activities.

An Easy Spectrophotometric Method for the Determination of Hypochlorite Using Thionin

Abstract: A simple, rapid, and sensitive spectrophotometric method has been developed for the determination of hypochlorite using thionin. The method is based on the reaction of hypochlorite with potassium iodide in acidic medium to liberate iodine. The liberated iodine bleaches the violet color of thionin, which is measured at 600 nm. The decrease in absorbance is directly proportional to the concentration of hypochlorite. Beer’s law is obeyed in the range 0.2– 1.2 µg/mL of hypochlorite. The molar absorptivity, Sandell’s sensitivity, detection limit, and quantitation limit are found to be 1.489 × 104 L/(mol cm), 3.25 × 10−3 µg cm−2, 0.1026 µg/mL, and 0.3112 µg/mL, respectively. The method has been successfully applied to the determination of hypochlorite in various samples of natural water, tap water, milk, etc.

A New Spectrophotometric Method for the Determination of Arsenic in Environmental and Biological Samples

Abstract: A simple and selective spectrophotometric method has been developed for the determination of trace amounts of arsenic using azure B as a chromogenic reagent. The proposed method is based on the reaction of arsenic(III) with potassium iodate in acid medium to liberate iodine. The liberated iodine bleaches the violet color of azure B and is measured at 644 nm. This decrease in absorbance is directly proportional to the As(III) concentration, and Beer's law is obeyed in the range 0.2–10 µg ml−1 of As(III). The molar absorptivity, Sandell's sensitivity, detection limit, and quantitation limit of the method were found to be 1.12×104 l mol−1cm−1, 6.71×10−3 µg cm−2, 0.02 µg ml−1 and 0.08 µg ml−1, respectively. The optimum reaction conditions and other analytical parameters were evaluated. The proposed method has been successfully applied for the determination of arsenic in various environmental and biological samples.

Rapid Spectrophotometric Determination of Trace Amounts of Chromium Using Variamine Blue as a Chromogenic Reagent

Abstract: Um metodo espectrofotometrico simples, rapido e sensivel foi desenvolvido para a determinacao traco de cromo usando azul de Variamina como reagente cromogenico. O metodo proposto consiste na reacao de cromo(VI) com iodeto de potassio, em meio acido, liberando iodeto que entao oxida o azul de Variamina formando um composto de cor violeta com o maximo de absorcao em 556 nm. A lei de Beer e obedecida na faixa de 2-12 mg mL-1 para Cr(VI). A absortividade molar, a sensibilidade de Sandell, o limite de deteccao e de quantificacao do metodo foram encontrados como sendo 0,911×104 L mol-1 cm-1, 1,14×10-2 mg cm-2, 0,02 mg mL-1 e 0,07 mg mL-1 respectivamente. As condicoes analiticas e otimas da reacao foram avaliadas. O efeito de ions interferentes na determinacao e descrita. O cromo(III) pode ser determinado depois da oxidacao a cromo (VI), com brometo em solucao aquosa alcalina. O metodo desenvolvido foi aplicado com sucesso na analise de cromo em ligas de aco, efluentes industrias, aguas naturais e amostras de solo.

Do C—H⋯O and C—H⋯π inter­actions help to stabilize a non-centrosymmetric structure for racemic 2,3-dibromo-1,3-diphenyl­propan-1-one?

Abstract: The racemic title compound, C15H12Br2O, crystallizes in a non-centrosymmetric structure and displays a significant non-linear optical response to red light. The crystal packing is influenced by C—H⋯O and C—H⋯π inter­actions. One of the former bonds has a short H⋯O separation of 2.27 A.

Synthesis of Some New 5‐(2‐Substituted‐1,3‐thiazol‐5‐yl)‐2‐hydroxy Benzamides and Their 2‐Alkoxy Derivatives as Possible Antifungal Agents.

Abstract: The 2-hydroxy-5-(1,3-thiazol-5-yl) benzamide (4a), 5-(2-amino-1, 3-thiazol-5-yl)-2-hydroxy benzamide (4b), 2-hydroxy-5-(2-alkyl-1,3-Thiazol-5-yl) benzamide (4c and 4d), 5-{2-[(N-substituted aryl)amino]-1,3-thiazol-5-yl}2-hydroxy benzamides (6a–j) were prepared by reacting 5-(bromoacetyl) salicylamide (2) with thiourea, thioformamide, thioalkylamide (3c–d) and substituted thioureas (5a–j) in absolute ethanol. These compounds were converted to 5-(2-substituted–1,3-thiazol-5-yl)-2-alkoxybenzamides and 5-(2-N-(substituted aryl)-1,3-thiazol-5-yl)-2-alkoxy benzamides (8a–g) by reacting with n-alkylbromides (7a–b) in presence of a base. The newly synthesized compounds were characterized by IR, 1H-NMR and mass spectral data. Compounds were also screened for their antifungal activity.

A facile spectrophotometric method for the determination of periodate using azure B

Abstract: Foi desenvolvido um metodo simples, rapido e sensivel para a determinacao de periodato em amostras de agua de rio e em solucao. O metodo e baseado na reacao do periodato com iodeto em meio acido, com liberacao de iodo. O iodo liberado diminui a intensidade da cor violeta do azure B, medida em 644 nm. O decaimento da absorbância e diretamente proporcional a concentracao de periodato e obedece a lei de Beer na faixa de 0,2 - 5,5 µg mL-1. A absortividade molar, a sensibilidade de Sandell e os limites de deteccao e de quantificacao encontrados foram 1,09x105 L mol-1 cm-1, 1,75x10-3 µg cm-2, 0,07 µg mL-1 and 0,20 µg mL-1, respectivamente. As condicoes otimas de reacao e os parâmetros analiticos foram avaliados. O efeito de ions interferentes e descrito. O metodo proposto foi aplicado com sucesso na determinacao de periodato em amostras de aguas de rio e em solucao.

Complexes of Ag(I), TI(I), Zn(II), Hg(II), Cd(II), Pd(II), Co(II) and Ni(II) with 4‐[(4‐Dimethylamino‐benzylidene)‐amino]‐5‐ethyl‐2,4‐dihydro‐[1,2,4]triazole‐3‐thione (HDEDT) and 4‐[(Benzylidene)amino]‐6‐(t‐butyl)‐4H‐[1,2,4]‐triazine‐3‐thione‐5‐one (HBBTT)

Abstract: The synthesis and characterization of complexes of Ag(I), Tl(I) Zn(II), Hg(II), Cd(II), Pd(II), Co(II) and Ni(II) with 4‐[(4‐dimethylamino‐benzylidene)‐amino]‐5‐ethyl‐2,4‐dihydro‐[1,2,4]triazole‐3‐thione (HDEDT) and 4‐[(benzylidene)amino]‐6‐(t‐butyl)4H‐[1,2,4]triazine‐3‐thione‐5‐one (HBBTT) are described. Octahedral structures are proposed for the Co(II) and Ni(II) complexes, tetrahedral ones for the Hg(II), Zn(II) and Cd(II) complexes, linear polymeric structures for the Ag(I) and Tl(I) complexes and a square‐planar structure for the Pd(II) complex. The ligand coordinates to the metal ions through the thiol sulfur after deprotonation and with the nitrogen of the azomethine group. The authors thank the Department of Chemistry, Kerala University, Thiruvananthapuram, India for TGA Studies, Regional Sophisticated Instrumentation Centre of Punjab University, Chandigarh for elemental micro analyses and the Microtron Centre, Mangalore University for UV‐Visible spectra.

Spectrophotometric determination of dissolved oxygen in water

Abstract: A simple, rapid and sensitive spectrophotometric method has been developed for the determination of dissolved oxygen (DO) in river water samples. The method is based on the reaction of dissolved oxygen with manganous sulphate in alkaline iodideazide solution and the liberation of iodine by manganese dioxide. The liberated iodine bleaches the violet colour of azure B which is measured at 644 nm. The decrease in absorbance is directly proportional to dissolved oxygen concentration and obeys Beer’s law in the range 0.2-1.4 μgmL. The molar absorptivity, Sandell’s sensitivity, detection limit and quantitation limit of the method were found to be 5.86 × 10 Lmol cm, 3.66 × 10 μg/cm, 0.030 and 0.090 μgmL, respectively.

A simple spectrophotometric determination of trace amounts of vanadium using thionin

Abstract: A simple and sensitive spectrophotometric method has been developed for the determination of trace amounts of vanadium using thionin as a chromogenic reagent. The proposed method is based on the reaction of vanadium(V) with potassium iodide in acid medium to liberate iodine, which bleaches the violet colour of thionin and is measured at 600 nm. This decrease in absorbance is directly proportional to the vanadium(V) concentration and obeys Beer\'s law in the range of 0.2-10 μgmL -1 of V(V). The molar absorptivity, Sandell\'s sensitivity, detection limit and quantitation limit of the method were found to be 2.298 x 10 4 Lmol -1 cm -1 , 0.52 x 10 -2 μgcm -2 , 0.035 μgmL -1 and 0.11 μgmL -1 , respectively. The optimum reaction conditions and other analytical conditions were evaluated. The effect of interfering ions on the determination is described. The developed method has been successfully applied to the analysis of the vanadium in synthetic and alloy samples. KEY WORDS: Vanadium determination, Spectrophotometry, Thionin Bull. Chem. Soc. Ethiop. 2005, 19(2), 155-161

Spectrophotometric determination of chromium using saccharin

Abstract: A sensitive and selective spectrophotometric method for the indirect determination of trace amounts of chromium(VI) is described. Chromium(V[) oxidizes hydroxylamine in acetate buffer of pH 4.0 to nitrite, which then diazotizes p-nitroaniline or sulphanilamide to form diazonium salt. These diazonium salts are then coupled with saccharin in an alkaline medium, which gives azo dye with absorption maximum at 372 and 390 nm for p-nitroaniline and sulphanilamide, respectively. The method obeys Beer's law in the concentration range of 1-16 μgmL - 1 for chromium with p-nitroaniline-saccharin and 0.6-14 μgmL - 1 of chromium with sulphanilamide-saccharin couples. The molar absorptivity, Sandell's sensitivity of the systems with p-nitroaniline-saccharin and sulphanilamide-saccharin couples were found to be 5.41×10 4 Lmol - 1 cm - 1 , 1.93×10 - 3 μgcm - 2 and 2.63×10 4 Lmol - 1 cm - 1 , 3.9×10 - 3 μgcm - 2 , respectively. The optimum reaction conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination was described. Chromium(III) can be determined after it is oxidized with bromine water in an alkaline medium to chromium(VI). The developed method has been successfully applied to the analysis of the chromium in alloy steel, pharmaceutical samples, natural water and soil samples.

1-(2-Bromo-5-methoxyphenyl)-8-chloro-6-(2-fluorophenyl)4H-1,2,4-triazolo[4,3-a][1,4] benzodiazepine

Abstract: The title compound, C23H15BrClFN4O, is an analogue of sedatives such as midazolam and alprazolam. Its geometrical parameters are normal and comparable with those of related compounds. The only possible significant inter­molecular inter­action is a C—H⋯O bond.