http://blogs.najah.edu/author/emp_2098 An-Najah Blogs :: en-us Fri, 19 Apr 2024 22:20:44 IDT Fri, 19 Apr 2024 22:20:44 IDT [email protected] [email protected] http://blogs.najah.edu/staff/emp_2098/article/Kinetics-and-Mechanism-of-Oxidation-of-L-Cysteine-by-FerrozineironIII-Complex-in-Aqueous-Acidic-MediumPublished ArticlesSee attached filehttp://blogs.najah.edu/staff/emp_2098/article/Atrazine-Detection-Using-Reflectometric-Interference-Spectroscopy-in-Several-Ground-and-Surface-Water-Samples-in-PalestinePublished ArticlesReflectometric interference spectroscopy RIFS was investigated for the detection of atrazine in several ground and surface water samples in Palestine The basic effect is white light interference at thin transparent films Chips were modified for covalent modofication of interference layers with atrazine-caproic acid Binding of proteins at the surface increases the optical thickness of the film which is detected as a change in the reflectance spectra A calibration curve was constructed and the results of analysis of all samples show the concentration of atrazine did not exceed 05ppbhttp://blogs.najah.edu/staff/emp_2098/article/A-catalytic-method-for-the-determination-of-trace-amounts-of-mercury-uptaken-by-broad-beams-plantsPublished ArticlesA new accurate fast catalytic method for the determination of trace amounts of mercury uptaken by plants is proposed The method is based on the catalytic effect of mercuryII on the rate of ligand-exchange reaction between ferrozine and hexacyanoferrateII whereby a coloured violet complex is formed which absorbs at 562 nm The method allows the determination of mercuryII in the range 005-40 ppm The effect of pH hexacyanoferrate ferrozine temperature time of reaction and tolerance limit of many ions have been reported The method is applied to the determination of mercuryII uptaken by broad beans plants irrigated with water containing different amounts of mercuryII http://blogs.najah.edu/staff/emp_2098/article/Preferential-solvation-of-Fephen2CN2-in-binary-aqueous-acetone-and-2-methoxyethanol-mixtures-Published ArticlesPreferential solvation ofbis-110-phenanthroline-bis-cyanoironII was investigated in aqueous acetone and 2-methoxyethanol binary mixtures The solvatochromic behaviour is discussed in terms of donor and acceptor numbers The thermodynamic model ofFrankel was used to treat preferential solvation in the binary aqueous 2-methoxyethanol mixtures and reveals that preferential solvation by the organic solvent occurs The preferential solvation constant at 29815K was found to be equal to 3300039 and the free energy of preferential solvation amounts to 296kJmole1http://blogs.najah.edu/staff/emp_2098/article/A-Sensitive-Catalytic-Method-for-the-Determination-of-Copper-by-Its-Catalytic-Effect-on-the-Potassium-Bromate-Indigo-Carmine-ReactionPublished ArticlesA method for catalytic determination of copper II is presented The method is based on the catalytic effect of copperII on the rate of oxidation of indigo carmine by potassium bromate The method is satisfactory for the determination of copperII in the range 12 to 38 ngmL Effect of acidity indigo carmine potassium bromate temperature and tolerance limits of foreign ions are reported The method was applied to the determination of copper in synthetic and in various milk sampleshttp://blogs.najah.edu/staff/emp_2098/article/Donor-and-acceptor-number-effects-for-the-solvatochromic-behaviour-ofbis-22prime-bipyridyl-bis-cyanoironII-in-binary-aqueous-mixturesPublished ArticlesCorrelation with acceptor numbers was made for the solvatochromic behaviour ofbis-22-bipyridyl-bis-cyanoironII in binary aqueous mixtures of acetonitrile andDMF The relationship between isosolvation point and donor number of the organic cosolvent was proved to be linear Preferential solvation occurs by water in the case of the binary acetonitrile mixtures and byDMF in the case of the binaryDMF aqueous mixtures http://blogs.najah.edu/staff/emp_2098/article/A-Spectroscopic-Study-of-Preferential-Solvation-of-Febipy2CN2-in-Binary-Aqueous-2-Ethoxy-Ethanol-MixturesPublished ArticlesPreferential Solvation of bis-22-bipyridyl biscyanoironII was investigated in 2-ethoxy ethanol water binary aqueous mixtures The treatment showed that preferential solvation by 2-ethoxy ethanol occurs The preferential solvation constant at 29815 K was found to be equal to 496 006 and the free energy of preferential solvations G has a value of 397 KJ mol-1http://blogs.najah.edu/staff/emp_2098/article/Kinetics-and-Mechanism-of-Oxidation-of-Cobalt-II-by-Iron-III-in-the-Presence-of-110-PhenanthrolinePublished ArticlesThe kinetics of oxidation of cobalt II by iron III in the presence of 1 10 phenanthroline has been investigated spectrophotometrically Hydrogen ions exhibited an inhibitory effect on the rate of the reaction while 110 phenanthroline showed an accelerating effect The order with respect to iron III was found to be unity On the other hand the order with respect to cobalt varies with its concentration being 03 0004 at high concentration and 0791-0019 at low concentrations A plausible mechanism was postulated and a rate law was derived that accounted for the various experimental results obtainedhttp://blogs.najah.edu/staff/emp_2098/article/Solvent-effects-and-correlation-with-ReichardtsET-values-on-charge-transfer-spectra-of-bis22prime-bipyridylbiscyanoironIIPublished ArticlesThe solvatochromic behaviour of biscyano-bis22-bipyridylironII in a variety of solvents is described The frequencies are correlated with Reichardts solvent parameterE T Various trends are indicated solvatochromic shifts of the title complex in various aqueous mixtures ofDMF and 2-butoxy ethanol are also reported Monatshefte fr Chemie Chemical Monthly Volume 124 Numbers 8-9 August 1993http://blogs.najah.edu/staff/emp_2098/article/Ironndashdiiminendashcyanide-complexes-as-probes-for-aqueous-micellar-systemsPublished ArticlesMedium effects on the charge-transfer bands of solvatochromic irondiiminecyanide complexes in aqueous micellar systems are described The observed shifts in max for these bands are discussed in terms of the charges on both the complexes and the surfactants and in relation to the critical micellar concentrations J Chem Soc Faraday Trans 199389 531 - 533 DOI: 101039FT9938http://blogs.najah.edu/staff/emp_2098/article/Solvatochromism-of-Ternary-Iron-II-Diimine-Cyanide-Complexes-in-2-Ethyl-2-hydroxymethyl-13-Propanediol-Trimethylol-PropanePublished ArticlesThe solvatochromic behaviour of bis-22-bipyridyl-biscyanoiron II and 22- bipyridyltetracyanoiron II in 2-ethyl-2-hydroxymethyl-13-propanediol has been established The significance and sensitivities of the solvatochromic shifts of these charge-transfer bands are outlined for the two iron complexes above Spectroscopy Letters Volume 26 Issue 1 January 1993 pages 129 - 135http://blogs.najah.edu/staff/emp_2098/article/Spectrophotometric-Determination-of-Trace-Amounts-of-Cobalt-and-Copper-with-3--2-Thiazolylazo--26--DiaminopyridinePublished ArticlesSensitive methods for the determination of trace amounts of cobalt and copper by complexation with 3-2-Thiazolylazo-26- diaminopyridine 26-TADAP are described Copper forms a 1:2 violet complex with the reagent having a molar absorptivity of 100 104 L mol-1cm-1 Baers law is obeyed over the range 0 -5084 g in the total volume of 10ml Cobalt also forms a 1:1 green complex with a molar absorptivity of 107 104L mol-1cm-1 and obeying Beers law over the range 0 -2357 g in the total volume of 10 ml The procedure is simple and rapid without any tedious extraction steps for copper and without oxidation of cobalt II to cobalt III Spectroscopy Letters Volume 25 Issue 7 November 1992 pages 1049 - 1055http://blogs.najah.edu/staff/emp_2098/article/Transfer-Chemical-Potentials-for-the-Sulfate-and-Tetracyano-22-BipyridylferrateII-Anions-for-Acetonitrile-Water-MixturesPublished ArticlesTransfer chemical potentials for the sulfate and tetracyano-22-bipyridylferrateII anions have been determined from measured solubilities of their respective silver and potassium salts in aqueous acetonitrile up to 40 acetonitrile at 2982 K JOURNAL OF CHEMICAL RESEARCH-SIssue: 8Pages: 288-289Published: AUG 1992http://blogs.najah.edu/staff/emp_2098/article/Effect-of-molybdenum-catalysis-on-the-perborate-bromide-reaction-Kinetics-and-mechanism-and-some-theoretical-considerationsPublished ArticlesIn the presence of molybdenum both the uncatalyzed and the catalyzed reactions proceed simultaneously An equation for kcat was derived and the effect of temperature was described through a temperature function FT by the use of the Arrhenius-Eyring equation A plausible mechanism is postulated and the theoretical background given for the analytical application of molybdenum Reaction Kinetics and Catalysis Letters Volume 48 Number 1 July 1992http://blogs.najah.edu/staff/emp_2098/article/Kinetics-and-mechanism-of-oxidation-of-bromide-ions-by-sodium-perborate-by-transforming-to-a-Landolt-process-Published ArticlesSodium perborate was used for oxidation of bromide ions at pH 364 The reaction was conducted by potentiometric measurements The orders with respect to perborate and bromide ions were found to be unity in each reagent and a plausible mechanism was postulated The effect of temperature was studied in the range of 2040 C and the Arrhenius parameters were evaluated Reaction Kinetics and Catalysis Letters Volume 48 Number 1 July 1992http://blogs.najah.edu/staff/emp_2098/article/Reactions-of-tris-diimine-and-diimine-cyanide-complexes-of-ironII-with-peroxoanions-in-solutionPublished ArticlesInvestigations of the kinetics of reactions of low-spin ironII-diimine-cyanide complexes with peroxodiphosphate peroxoborate and peroxomonosulphate suggested that only the last-named could act by rate-determining oxidation Peroxodiphosphate and perborate react by rate-limiting dissociation with the subsequent rapid oxidation of the products of this dissociation The reactivity trend for peroxomonosulphate oxidation of the [FeCN4bipy]2 anion in water-acetonitrile mixtures is reported and analysed into initial state and transition state contributions with the aid of appropriate assumptions Polyhedron Volume 11 Issue 16 1992 Pages 2015-2019 http://blogs.najah.edu/staff/emp_2098/article/Catalytic-Determination-of-Molybdenum-by-Means-of-the-Sodium-Perborate-Bromide-Ascorbic-Acid-Landolt-Reaction-Using-Potentiometric-MeasurementsPublished ArticlesA new catalytic method for the determination of 01-10 ppm molybdenum is described Molybdenum catalyses the perborate - bromide ascorbic acid Landolt reaction at pH 364 The rate is monitored by potentiometry A calibration graph is based on the ratio of the reaction times for the blank and the sample totc plotted against the concentration of molybdenum Optimal conditions for the determination are discussed Also the effect of various ions and interferences are described ANALYTICAL LETTERSVolume: 25Issue: 6Pages: 1111-1118Published: 1992http://blogs.najah.edu/staff/emp_2098/article/Kinetics-and-Mechanism-of-the-Hydrolysis-of-Benzylidene-Benzoylhyd---Razone-DerivativesPublished ArticlesThe kinetics and mechanism of hydrolysis of a series of substituted benzylidene benzoylhydrazones X BBH have been studied at five different temperatures in the range 25 45c by U V -visible spectrophotometry The hydrolysis reactions were found to follow first - order kinetics A mechanism has been postulated in which the attack of water on the protonated substrate is subject to general base catalysis This mechanism has been supported by the effect of anion concentration of buffer at constant pH on the observed rate constant The Bronsted -value for the hydrolysis reaction is 073 Hammett correlations Arrhenius and thermodynamic parameters have been evaluated and discussed The pKa values for the conjugate acids for benzylidene benzoylhydrazones derivatives X - BBH have been determinedhttp://blogs.najah.edu/staff/emp_2098/article/The-Mass-Spectra-and-Disproportionation-Studies-of-a-Nitrogen-Compound-of-Mercury-I-with-110-Phenanthroline-Published ArticlesA nitrogen compound of mercury 1 was prepared by reaction of 110 phenanthroline with mercurous nitrate The mass spectra of this resulting precipitate was made and its distinguished features have been discussed The results of various investigations suggest that disproportionation of the HgI state did not occur Spectroscopy Letters Volume 21 Issue 7 August 1988 pages 509 - 518http://blogs.najah.edu/staff/emp_2098/article/Kinetic-Study-of-the-Complexation-of-Palladium-II-with-2-5-Bromo-2-Pyridylazo-5-DiethylaminophenolPublished ArticlesThe kinetics of the complexation reaction of palladium with 2-5-bromo-2-pyridylazo-5-diethylaminophenol 5-Br-PADAP has been studied in the stability time at the optimum pH of 353 in presence of 50 ethanol The effect of ionic strength and temperature on the reaction rate were reported A mechanism has been postulated and the stability constants of the individual steps were determined The Arrhenius and thermodynamic parameters were evaluated and discussedhttp://blogs.najah.edu/staff/emp_2098/article/Spectrophotometric-determination-of-cadmiumII-using-2-5-bromo-2-pyridylazo-5-diethylaminophenol-Published ArticlesThe complex of cadmium with the reagent 2--5-bromo-2-pyridylazo-5-diethylaminophenol 5-Br-PADAP has been studied The composition stability constant and free energy change of formation of the complex have been determined A sensitive spectrophotometric method for the determination of cadmium has been developed and applied for a range of concentration of 0440 gml cadmium using the complex Cd-5-Br-PADAP The optimum conditions for maximum sensitivity of determination such as standing time pH wavelength and order of addition have been determined The effect of foreign ions on this method has been also studied Microchemical Journal Volume 34 Issue 3 December 1986 Pages 251-253 http://blogs.najah.edu/staff/emp_2098/article/Spectrophotometric-Determination-of-Trace-Amounts-of-Mercury-with-3-2-Thiazolylazo-2-6-Diaminopyridine-and-GelatinePublished ArticlesA sensitive method for the determination of trace amounts of mercury by complexation with 3-2-Thiazolylazo-2 6-diaminopyridine 2 6-TADAP is described HgII forms a 1:2 complex with the reagent Beers law is obeyed over the range 5-40 g in the total volume of 10 ml The molar absorptivity was found to be 14 104 L mol-1 cm-1 This method is simple rapid and involves no extraction steps whereby the use of gelatine as a solubilizing agent is described Spectroscopy Letters Volume 19 Issue 8 October 1986 pages 929 - 937http://blogs.najah.edu/staff/emp_2098/article/Selective-Spectrophotometric-Determination-Of-PalladiumII-With-2-5-Bromo-2-Pyridylazo-5-Diethylamino-PhenolPublished ArticlesANALYTICAL LETTERSVolume: 19Issue: 1-2Pages: 99-112Published: 1986http://blogs.najah.edu/staff/emp_2098/article/Sensitive-spectrophotometric-determination-of-bismuthIII-with-2-5-bromo-2-pyridylazo-5-diethylaminophenolPublished ArticlesThe complex of the reagent 2-5-bromo-2-pyridylazo-5-diethylaminophenol 5-Br-PADAP with BiIII has been studied The composition and stability of this complex have been determined An analytical method for the spectrophotometric determination of BiIII using its complex with 5-Br-PADAP has been developed Variables influencing the method such as pH wavelength and time have been studied The limitations of this method and the effect of interfering ions have been investigated Comparison of this method with other methods cited in the literature for the determination of BiIII is also included Microchemical Journal Volume 32 Issue 1 August 1985 Pages 83-88http://blogs.najah.edu/staff/emp_2098/article/The-thermal-decomposition-of-fluorinated-esters-III-Esters-without-beta-hydrogen-atomsPublished ArticlesThe kinetics of the gas-phase decomposition of methyl trifluoroacetate and 222-trifluoroethyl trifluoroacetate two esters without hydrogen atoms have been investigated and a comparative study was carried out on methyl acetate All these compounds are thermally much more stable than fluorinated esters with hydrogens decomposing at temperatures some 150C above the latter by a completely different mechanism involving partly heterogeneous radical chains The marked difference in behavior between the two types of fluorinated ester confirms that none of them decomposes by hydrogen fluoride elimination but that those with hydrogen atoms follow the normal ester decomposition route The fluorinated esters examined here decompose in a manner generally similar to methyl acetate but the presence of fluorine in the molecule brings about an extreme sensitivity to surface conditionshttp://blogs.najah.edu/staff/emp_2098/article/The-thermal-decomposition-of-fluorinated-esters-II-The-effect-of--substitutionPublished ArticlesThe gas-phase kinetics of thermal decomposition of ethyl difluoroacetate pentafluoropropionate and hepatfluorobutyrate have been studied The normal ester decomposition route to ethylene plus carboxylic acid is taken in each case but the fluorinated acids decompose rapidly at the temperatures used The primary decompositions are homogeneous and unimolecular and the three Arrhenius equations are The postulate of a slightly electron-rich carbon in six-center ester transition states is supported by the higher rates and lowered activation energies observed when increasingly electron-withdrawing fluorinated groups are linked to this center The stabilization is reflected in a constant of 030 The results are compared with previous work on substitution in fluorinated estershttp://blogs.najah.edu/staff/emp_2098/article/The-thermal-decomposition-of-fluorinated-estersPublished ArticlesThe kinetics of thermal decomposition of ethyl isopropyl and t-butyl trifluoroacetates have been studied in the gas phase In each case initial decomposition follows the normal ester route to give an olefin and trifluoroacetic acid and elimination of hydrogen fluoride does not occur However trifluoroacetic acid is thermally unstable at ethyl and isopropyl ester decomposition temperatures and further products result including those from the difluorocarbene produced by decomposing trifluoroacetic acid Placing a CF3 group at an esters carbon increases the polarity of its transition state and decreases its thermal stability The activation energies of the ethyl and isopropyl esters are lowered by 38 and 47 kcalmol compared to the corresponding acetates and the primary decomposition kinetics which are homogeneous and of the first order are expressed by -Methylation enhances the reactivity of the trifluoroacetates and the t-butyl ester the transition state for which is sufficiently polar for heterogeneous decomposition to occur shows signs of thermal instability at room temperature The equilibrium was also investigated and gave H = 13580 calmol and S = 3107 gibbsmol in the forward direction The results obtained extend and support the known structure-rate correlations in the gas-phase elimination of esters