Browsing by Autor "Tewari, Brij B"

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A CRITICAL REVIEW ON OCIMUM TENUFLORUM, CARICA PAPAYA AND SYZYGIUM CUMINI: THE MEDICINAL FLORA OF GUYANA
(Rev. Bol. Quim, 2014) Tewari, Brij B; Gomathinayagam, Subramanian
COMPLEX FORMATION OF SOME DIVALENT METAL IONS WITH OXYGEN DONOR LIGANDS
(Rev. Bol. Quim, 2009) Tewari, Brij B
Complexation reaction of a-aminobutyric acid with beryllium(II) and cobalt(II) have been studied in solution phase using paper electrophoretic technique. This method is based on the movement of a spot of metal ion in an electric field at various pH's of the background electrolyte. A plot of overall mobility of metal / complex ion versus pH was used to obtain information on the binary complexes and to calculate stability constants. The stability constant of the ML and ML2 complexes of beryllium(II) - a-aminobutyric and cobalt(II) - a-aminobutyric acid have been found to be (7.19 ± 0.05, 6.81 ± 0.13) and (4.47 ± 0.04, 2.81 ± 0.09) (logarithm stability constant values), respectively at 35°C and ionic strength 0.1 M
ELECTROPHORETIC STUDIES ON MEDICINALLY IMPORTANT BINARY METAL COMPLEXES (SYSTEM: COPPER(II) / MANGANESE(II) / URANYL(II) - SARCOSINE)
(Rev. Bol. Quim, 2008) Tewari, Brij B
Quantitative indication of the process of forming a complex comes from the evaluation of the stability constants which characterize the equilibria corresponding to the successive addition of ligands. A technique involving the use of paper electrophoresis is described for the study of binary complex system in solution. The first and second stability constants of metal(II) - sarcosine complexes were found to be (7.82 ± 0.07, 6.90 ± 0.03); (3.54 ± 0.11, 1.96 ± 0.02) and (7.41 ± 0.06, 5.57 ± 0.03) (log stability constant values) for Cu(II), Mn(II) and UO2(II) complexes, respectively
INTERACTION OF (AMINOBUTENOIC ACID WITH DIVALENT BERYLLIUM(II) AND COBALT(II) IN CHEMICAL AND BIOLOGICAL SYSTEMS
(Rev. Bol. Quim, 2010) Tewari, Brij B
Paper electrophoresis has been applied to the study of metal complexes in solution and attempts have been made to determine the stability constants of complex species. The proportion of ionic species of (-aminobutenoic acid was varied by changing the pH of background electrolyte. The stability constants of ML and ML2 complexes of Be(II) - (-aminobutenoic and Co(II) - (-aminobutenoic acid complexes were found to be (7.19 ± 0.09, 5.91 ± 0.11) and (4.19 ± 0.03, 3.57 ± 0.07) (logarithm stability constant values), respectively at ionic strength 0.1 Mol L-1 and a temperature of 35° C. Corresponding author:"mailto:brijtew@yahoo.com"brijtew@yahoo.com
Revisiones críticas sobre la estabilidad y el potencial Fotosensibilizante de los ferrocianuros metálicos: un posible mineral prebiotico; parte (II)
(Rev. Bol. Quim, 2018) Tewari, Brij B; Usmanali, D; Webster, Rawl W; Kadir, I; Tiwari, Ashish K; Ramchurjee, N
Los ferrocianuros de aluminio, bario, cromo, indio, platino, estannoso y vanadio se sintetizaron y caracterizaron mediante analisis elemental y estudios espectrales. La estabilidad de los ferrocianuros metalicos sintetizados se registro en calor, luz (UV, VIS), diversas concentraciones de acidos (HCl, H2SO4), diversas concentraciones de bases (NaOH, KOH, NH4OH), agua de mar y del grifo a temperatura ambiente y de ebullición. La estabilidad de los ferrocianuros metalicos sintetizados tambien se registro en disolventes organicos (eter, acetona, etanol, formaldehído) a temperatura ambiente. El potencial oxidante y fotosensibilizador de ferrocianuros metalicos sintetizados se analizaron usando yoduro de potasio y solución de almidón recien preparada. Los complejos de hexacianoferrato (II) de cromo, indio y platino se encontraron como posibles oxidantes y fotosensibilizadores durante el curso de la evolución química en la tierra primitiva.
STUDIES ON BIOLOGICALLY IMPORTANT CADMIUM (II) / IRON (II) / ZINC (II) - HOMOSERINE BINARY COMPLEXES IN SOLUTION
(Rev. Bol. Quim, 2014) Tewari, Brij B
In coordination compounds studies, knowledge of the magnitude of the stability constants of complexes is necessary for preliminary quantitative treatment. The present technique involving the use of paper electrophoresis is described for the study of equilibria in binary complex systems in solution. This method is based on the movement of a spot of metal ion in an electric field at various pH's of background electrolyte. A graph of pH versus mobility was used to obtain information on the binary complexes and to calculate its stability constants. The stability constants of the ML and ML2 complex species of some metal ions, namely cadmium (II), iron (II) and zinc (II) with homoserine were determined in 0.1 mol / L perchloric acid and at a temperature of 35 °C. The logarithm stability constants of the ML and ML2 complexes of homoserine were found to be (3.91 ± 0.03, 2.58 ± 0.09), (3.57 ± 0.01, 2.45 ± 0.05) and (4.33 ± 0.01, 2.70 ± 0.07)( logarithm stability constant values) for the cadmium(II), iron(II) and zinc(II) complexes, respectively.
STUDIES ON MERCURY(II), NICKEL(II) AND LEAD(II) BIOLOGICALLY IMPORTANT BINARY COMPLEXES WITH NORVALINE IN SOLUTION
(Rev. Bol. Quim, 2011) Tewari, Brij B
A recent technique involving the use of paper electrophoresis is described for the study of equilibria in binary complex systems in solution. This method is based on movement of a spot of metal ion in an electric field at various pHs of background electrolyte. A graph of pH versus mobility give the information for binary complexes and to calculate stability constants. The logarithm stability constants of the ML and ML2 complexes of norvaline were found to be (8.61 ± 0.03; 7.05 ± 0.07), (6.93 ± 0.05; 5.47 ± 0.03) and (4.57 ± 0.02; 3.00 ± 0.05) for the mercury(II), nickel(II) and lead(II) complexes, respectively at ionic strength 0.1 M perchloric acid and a temperature of 35 ° C