| Author (s): |
Lavinel G. Ionescu
|
| Title: |
A TRIBUTE TO PROFESSOR CLIFFORD A. BUNTON ON HIS 80th BIRTHDAY |
| Abstract: |
On January 4, 2000, Professor Clifford A. Bunton will celebrate his 80th birthday, over fifty years of contributions to mechanistic organic chemistry and more than thirty years of work on the structure and reactivity of micelles and other associations colloids. He obtained the B.So. Degree in Chemistry from University College, London in 1941 and the Ph.D. Degree in mechanistic organic chemistry from the same institution in 1944. He remained there as Lecturer and Reader until 1963 when he joined the faculty of the University of California, Santa Barbara, where he is at the present an Emeritus Professor. Professor C.A. Buntons research work centers on the physical organic chemistry of carboxylate and phosphate ester hydrolysis, micellar catalysis, kinetic isotope effects, and reactions of ferrocenyl carbocations. He had a large number of students and collaborators from all continents and all corners of the globe and published hundreds of scientific works.
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| Keywords: |
History of Chemistry, Carboxylate and Phosphate Ester Hydrolysis, Micellar Catalysis, Isotope Effects, Mechanistic Organic Chemistry.
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| Year: |
1999
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| Initial page: |
1
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| Final page: |
10
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.4_1999.pdf |
|
|
| Author (s): |
Marcia M. Meier, Patricia Karloh, Heman Terenzi, Bruno Szpoganicz
|
| Title: |
EQUILIBRIUM AND HYDROLYSIS STUDIES OF PHOSPHATE ESTERS MODEL MOLECULES AND DNA CATALYZED BY OBISDIEN-Zn(II) COMPLEXES. |
| Abstract: |
Dinuclear Zn(II)-OBISDIEN complexes catalyze hydrolysis of DNA and a phosphate ester model molecule: bis(2,4-dinitrophenyl)phosphate (BDNPP). The increase in the rate of hydrolysis of BDNPP at pH values above 8.0 is attributed to the presence of a ternary hydroxide species, in which intramolecular catalysis is favored by the proximity of the hydroxide group coordinated to the bimetallic center of the receptor complexes, in agreement with equilibrium results of OBISDIEN-Zn(II)-ATP (1:2:1 molar ratio) system. In the treatment of pBR322 circular DNA with OBISDIEN-Zn(II) complexes, the results suggest that these complexes cleave DNA in a random and nonspecific manner since no distinguishable low molecular weight bands were observed after treatment
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| Keywords: |
hydrolysis, DNA, bis(2,4-dinitrophenyl)phosphate, ATP.
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| Year: |
1999
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| Initial page: |
11
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| Final page: |
23
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.14_1999.pdf |
|
|
| Author (s): |
I Panea, Lucia Bodochi, Teodora Panea, Daniela Zinveliu and Violeta Pascalau
|
| Title: |
BIOLOGICAL ACTIVE ACYLHYDRAZIDE I. THE O-ACYL-DERIVATIVES NATURE OF MONOACYLATION PRODUCTS OF CYCLIC MALEIC- AND PHTHALIC-HYDRAZIDE |
| Abstract: |
We confirmed, on the basis of chemical and physicochemical (melting points, IR- and 1H-NMR-spectra) data, that the products isolated by monoacylation of cyclic maleic- and phthalic-hydrazides have only the O-acyl derivatives nature although owing to tautomerism. These hydrazides may give rise to N- or/and O-acyl derivatives in such reactions. Simultaneously, we showed that the claims for the obtainment of N-acyl derivatives of cyclic maleic- and phthalic-hydrazides were not valid. Also by reacting the cyclic maleic-, respectively phthalic-hydrazide, with 4-chlorobenzoylchloride two new O-monoacylderivatives [3-( 4-chlorobenzoyloxy)-l-H-pyridazin-6-one and 1-(4-chlorobenzoyloxy)-3-H-phthalazin-l-one] were obtained
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| Keywords: |
O-acylderivatives of cyclic maleic- and phthalic-hydrazides, Melting points, IR- and 1H-NMR-spectra.
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| Year: |
1999
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| Initial page: |
25
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| Final page: |
40
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.27_1999.pdf |
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|
| Author (s): |
Luzia Otilia Bortotti Favero, Ervim Lenzi, Eduardo Bernardi Luchese, e Luciano Marcio de Moraes
|
| Title: |
BORON EXTRACTORS EVALUATION |
| Abstract: |
Samples of six types of soil were tested in a greenhouse. Three doses of boric acid: 0.0 g (control); 0.10 g and 0.20 g were applied to the prepared soils. Seeds of cabbage were sown and only two plants remained after cutting. Mehlich 1, HCl 0.05 mol.L-1, and the saturation extract were used to determine the boron in the soil. After determining the dry matter and calcined the plants ashes were dissolved in HCl 0.6 mol.L-1. The boron concentration was determined by the Azomethine-H method The correlation between boron .concentration in the plant (μg.g-1 ) and total boron in the plant (μg.plant-1 ) versus boron concentration in the soil showed that among the three extractors the HCl O.05 mol.L-1 and saturation extract presented the best correlation coefficients (r): 0.857 and 0.832, 0.858 and 0.841 respectively. The Mehlich I extractor presented the lowest correlation coefficients for all conditions studied
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| Keywords: |
boron extractors, micronutrient, boron, element extraction, boron in soil.
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| Year: |
1999
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| Initial page: |
41
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| Final page: |
49
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.43_1999.pdf |
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|
| Author (s): |
CLAUDIA A. L. CARDOSO, WAGNER VILEGAS AND NELI K. HONDA
|
| Title: |
QUANTITATIVE DETERMINATION OF FURANOCOUMARINS AND IDENTIFICATION OTHER CHEMICAL CONSTITUENTS OF RHIZOMES AND LEAVES FROM DORSTENIA TUBICINA AND COMMERCIAL SAMPLES |
| Abstract: |
The chemical composition of the hexane extracts from the rhizomes and leaves of Dorstenia tubicina Ruiz et Pavon (Moraceae) and four commercial samples of Dorstenia was investigated by high-resolution gas chromatography-flame ionization detector (HRGC-FID) and high-resolution gas chromatographic-mass spectrometry (HRGC-MS). This is a rapid and sensitive method for the quantification of furanocoumarins and identification isoprene derivatives (triterpenes, steroids, and vitamins) from apolar crude extracts of Dorstenia species
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| Keywords: |
Dorstenia tubicina, furanocoumarins, gas chromatography-mass spectrometry, steroids, triterpenes, vitamins.
|
| Year: |
1999
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| Initial page: |
51
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| Final page: |
60
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.52_1999.pdf |
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|
| Author (s): |
Neli K. Honda, Rosenei L. Brum, Maria Rita Marques, Marcelo P. Marcelli, Mariana Fleig, Wagner Vilegas
|
| Title: |
FUNGITOXIC ACTIVITY OF COMPOUNDS ISOLATED FROM LICHENS |
| Abstract: |
Lichens collected in Mato Grosso do Sul, Brazil was analyzed to their secondary metabolites. The compounds isolated were tested against the phytopathogenic fungus Cladosporium sphaerospermum, using a bioautography test. Diffractaic acid, atranorin/chloroatranorin, usnic acid, and the technical artifact product ethyl orselinate inhibited the fungus growth
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| Keywords: |
lichens, fungitoxic activity, Cladosporium sphaerospermum, secondary metabolites..
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| Year: |
1999
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| Initial page: |
61
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| Final page: |
66
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.62_1999.pdf |
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|
| Author (s): |
Maria Pleniceanu, Luminita Simoiu, Marian Isvoranu, Mihaela Baniceru
|
| Title: |
LIQUID MEMBRANE ION-SELECTIVE ELECTRODES FOR POTENTIOMETRIC DOSAGE OF SOME METAL IONS |
| Abstract: |
Four electrodes with liquid membrane, Cu2+ selective and Ni2+ selective, not described previously in the literature, were prepared and characterized. From these electrodes, I and 2 are based on simple complexes of Cu(II) and Ni(II) with 2,3-dithio-6-nitro-benzoquinoxaline-5,10-dione (dtnbqd), as ligand belonging to the dithiol class. Electrodes 3 and 4 are based on the corresponding mixed complexes in which the ammonia molecule acts as the second ligand and 2,3-dithio-6-nitro-benzoquinoxaline-5,10-dione as the first ligand.
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| Keywords: |
copper, nickel, liquid-membrane electrodes, potentiometry, selectivity..
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| Year: |
1999
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| Initial page: |
67
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| Final page: |
77
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.68_1999.pdf |
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|
| Author (s): |
Rogerio B. Brasil, Claudenice Rodrigues, and Jorge Nozaki
|
| Title: |
RECOVERY OF MERCURY FROM DENTAL AMALGAMS COLLECTED IN THE NORTHWEST REGION OF PARANA STATE, BRAZIL |
| Abstract: |
Wastes amalgams were collected from dental cabinets of the northwest region of the Parana State, Brazil. Amalgams collected were washed with 0.1M nitric acid and distilled water, dried at 80°C, and crushed to 1OO mesh. Digestion of the brown powder was performed using two types of reactors. The first was made of pyrex glass and the second reactor of stainless steel, both connected to a PVC tube with Mn02 and a vacuum pump. The efficiency observed was higher for the second reactor, with 96-98% of mercury recovered, and the minimum time necessary for digestion was 180 minutes. After the digestion, the mercury was transferred to a conventional apparatus for mercury distillation and purification. The distillation was performed two times and the final mercury recovered was 99% pure. Silver and tin were also recovered by chemical and electrochemical methods after the mercury separation.
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| Keywords: |
dental amalgams, mercury; environment; pollution; metal recovery.
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| Year: |
1999
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| Initial page: |
79
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| Final page: |
86
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.79_1999.pdf |
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|
| Author (s): |
Carmem D. Cardoso, Martha B. Adaime and Nadia S. Viaro
|
| Title: |
HEIGHT MEASUREMENTS OF THE SPECTRUM AS AN ALTERNATIVE TO CONVENTIONAL SPECTROPHOTOMETRIC ANALYSIS OF A KMnO4K2Cr2O7 MIXTURE |
| Abstract: |
Quantitative spectrophotometric analysis is generally carried out plotting absorbance against concentration, for some concentration range, in accordance with Lambert, Bourger and Bee law. In this work, height measurement of the spectrum was used to analyse KMn04 and K2Cr207 mixtures in two different known concentrations. The experiments were relatively simple to carry out, requiring only standard solutions of KMn04, K2Cr207, sample mixtures of the two components, a visible light spectrophotometer, recorder, ruler and pencil. Comparison of the two methods showed that the height measurement method is more reliable and versatile as it has no requirement for the calculation of molar absorptivity, shows less relative error than the conventional method.
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| Keywords: |
Height measurements, spectrophotometric analysis, KMn0
4-K
2Cr
2O
7 mixture, quantification.
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| Year: |
1999
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| Initial page: |
87
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| Final page: |
94
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.87_1999.pdf |
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|
| Author (s): |
Adalgiza Ciobanu, Florica Zãlaru, D.Albinescu, Christina Zãlaru
|
| Title: |
COORDINATION COMPOUNDS OF Cu(II) AND Ni(II) WITH SCHIFF BASES DERIVED FROM FORMYLMENTHONE AND o-, m-,p-TOLUIDINE |
| Abstract: |
The Schiff bases obtained from formylmenthone and o-, m-, p-toluidine behave as bidentate ligands with O and N donor atoms in Ni(II) and Cu(II) complexes by the type NiL2 and CuL2.(H2O)2. The donor atoms and the possible geometry for the complexes were assigned by means of chemical, thermodifferential analyses and electronic, EPR and IR spectra
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| Keywords: |
Coordination compounds of Cu(II) and Ni(II), Schiff bases derived from formylmenthone.
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| Year: |
1999
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| Initial page: |
95
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| Final page: |
104
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.95_1999.pdf |
|
|
| Author (s): |
Lavinel G. Ionescu, Silvia Dani, and Elizabeth Fatima de Souza
|
| Title: |
PHYSICAL CHEMICAL STUDIES OF THE AGGREGATION AND CATALYTIC PROPERTIES OF THE SURFACTANT CETYLDIMETHYLETHYLAMMONIUM BROMIDE (CDEAB) |
| Abstract: |
The micellization of cetyldimethylethylammonium bromide (CDEAB) in water was studied by means of surface tensiometry. The critical micellar concentration (CMC) was determined at 25°, 32°, and 40°C, and thermodynamic properties such as the free energy of micellization (∆G°mic), enthalpy (∆H°mic) and entropy (∆S°mic) of micellization were measured. The CMC at 25°C was 9.05 x 10-4 M and the corresponding values of the thermodynamic parameters were: ∆G°mic = -4.15 kcal/mol; ∆H°mic = -1.37 kcal/mol and ∆S°mic = + 9.33 e.u. Micelles of the surfactant CDEAB were good catalysts for the alkaline hydrolysis of p-nitrophenyl diphenyl phosphate (NPDPP) with a maximum catalytic factor of approximately 80, comparable to that of CTAB. Typical activation parameters measured for 0.005 M NaOH were: Ea = 9.0 kcal/mol; ∆H°≠ = 8.4 kcal/mol; ∆G°≠ = 19.2 kcal/mol and ∆S°≠ = -36.3 e.u. The kinetic results were also analyzed in terms of the pseudo-phase ion-exchange models (PPIE) and showed that the model is applicable and gave reasonable fits
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| Keywords: |
cetydimethylethylammonium bromide; micellization; micellar catalysis; phosphate esters.
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| Year: |
1999
|
| Initial page: |
105
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| Final page: |
114
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v7.n8.1999.105_1999.pdf |
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