Physical Sciences and Mathematics Commons^™

Kinetics Of Oxidation Of Pyridylmethylsulphinylbenzimidazole By Cerium(Iv) In An Aqueous Perchloric Acid Medium, Dinesh C. Bilehal, Ravi̇raj M. Kulkarni, Sharanappa T. Nandibewoor

Turkish Journal of Chemistry

The kinetics of oxidation of pyridylmethylsulphinylbenzimidazole [PMSB] by Ce(IV) in an aqueous perchloric acid medium at a constant ionic strength of 1.50 mol dm^{-3} were studied spectrophotometrically. The reaction showed first order kinetics with respect to Ce(IV) concentration and an apparent less than unit order dependence in [PMSB] and a zero order in [H^+]. The initial addition of products has no significant effect on the rate of the reaction. A possible mechanism is proposed here. The reaction constants involved in the mechanism have been computed. There is good agreement between the observed and calculated rate constants under different experimental conditions. …

Electrochemistry And Spectroscopy Of Sulfate And Thiosulfate Complexes Of Iron Porphyrins, Philip Walter Crawford, Michael D. Ryan

Chemistry Faculty Research and Publications

The electrochemical and spectroscopic properties of the complex formed by the addition of thiosulfate to ferric porphyrins were examined. The NMR spectrum of the thiosulfate–ferric porphyrin complex was consistent with a high-spin ferric complex, while the EPR spectrum at liquid nitrogen temperatures indicated that the complex under these conditions was low-spin. Such behavior has been previously observed for other ferric porphyrin complexes. The visible spectra were characterized by a shift in the Soret band to higher energies, with smaller changes in the longer wavelength region. The complex was reasonably stable in DMF, but slowly reduced over several hours to Fe …

The Kinetics And Mechanism Of Oxidation Of Vanillin By Diperiodatonickelate(Iv) In Aqueous Alkaline Medium, Chandrashekhar Kathari, Pandurang Pol, Sharanappa Nandibewoor

Turkish Journal of Chemistry

The title reaction was investigated in aqueous alkaline medium. A first order dependence in diperiodatonickelate (IV) (DPN) and an apparent fractional order in both vanillin and alkali were obtained. Periodate has a retarding effect on the reaction. The effect of added products and the ionic strength of the reaction medium have no significant effect on the reaction rate. A decrease in the dielectric constant of the medium decreases the rate of reaction. Effects of temperature on the rate of reaction were studied. A mechanism based on experimental results was proposed, and constants involved in the mechanism were evaluated. A good …

Oxidation Of Ethylenediaminetetraacetic Acid By N-Bromosuccinimide In Aqueous Alkaline Medium -- A Kinetic Study, S. K. Mavalangi, M. R. Kembhavi, S. T. Nandibewoor

Turkish Journal of Chemistry

The kinetics of oxidation of ethylenediaminetetraacetic acid (EDTA) by N-bromosuccinimide (NBS) in aqueous alkaline media was investigated at 25°C. Analysis of the results showed the reaction is first -- order with respect to [NBS] and apparently less than unit order each with respect to [EDTA] and [alkali]. The influence of the reaction products, ionic strength, temperature effect and dielectric constant of the medium on the rate of reaction was studied. The proposed mechanism is consistent with the observed kinetics. The reaction constants involved in the mechanism were derived. There is a good agreement between the observed and calculated rate constants …

Kinetics And Thermodynamics Of Oil Extraction From Sun Ower Seeds In The Presence Of Aqueous Acidic, Hüseyi̇n Topallar, Ümi̇t Geçgel

Turkish Journal of Chemistry

Oil extraction was performed in aqueous HCl, H_2SO_4 and H_3PO_4 solutions with n-hexane (C_6H_{14}) at 30, 40, 50 and 60 ^oC using 10 gr of sunflower seeds over 1 h with 10-min. sampling intervals. The optimum acid concentration was wt. 10% for each acid, and the highest oil yield was obtained in the extraction procedure with n-hexane containing H_2SO_4. The extraction process was observed with regard to the percent oil yield versus time, and the reaction order was found to be first-order kinetics by the differential method. The activation energy for the oil extraction kinetics of sunflower seeds with 10% …

Folding Under Inequilibrium Conditions As A Possible Reason For Partial Irreversibility Of Heat-Denatured Proteins: Computer Simulation Study, Sergey A. Potekhin, Evgueni Kovriguine

Chemistry Faculty Research and Publications

Using computer simulations we have studied possible effects of heating and cooling at different scan rates on unfolding and refolding of macromolecules. We have shown that even the simplest two-state reversible transition can behave irreversibly when an unfavorable combination of cooling rate, relaxation time and activation energy of refolding occurs. On the basis of this finding we suppose that apparent irreversibility of some proteins denatured by heat may result from slow relaxation on cooling rather than thermodynamic instability and/or irreversible alterations of the polypeptide chain. Using this kinetic reversible two-state model, we estimated the effects of the scan rate and …

A Kinetic Study Of The Photolysis Of Ethylferrocene In Chloroform, Son L. Phan, Patrick E. Hoggard

Chemistry and Biochemistry

The photooxidation of ethylferrocene to ethylferricinium ion and tetrachloroferrate in CHCl3 under 254 nm irradiation proceeds through light absorption by both ethylferrocene and chloroform. The products remain in solution at concentrations below 10-3 M. The fraction occurring through a solvent-initiated pathway increases during the course of the reaction. A secondary thermal reaction is responsible for generating tetrachloroferrate from ethylferricinium ion. The rate of the reaction increases during the early stages, and the data throughout the course of the reaction are consistent with the rate law ( afs + bfR)/ (1 + c[R]/[P]-d[R]/[Cl ]), where [R] and [P] are the concentrations …

Thermodynamics And Kinetics Of Small Molecule Binding To [Cyclopentadienyl-Ru-No] And [Rh-Co] Electrophilic Centers, Anna Svetlanova

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This work is concentrated on the thermodynamic and kinetic aspects of water, alcohols, alkyl halides, ethers, and lactones bound and activated by the electrophilic [Cp'Ru(N0)]⁺² and [Cp’Ru (NO)(CH₃)] + centers (Cp' = cyclopentadienyl group). Counterions in these systems include OSO₂CF₃- (OTf`) and [(3, 5-(CF₃)₂C₆H₃)₄B]- ([BAr₄']-). The displacement of OTf- in Cp'Ru(N0) (0Tf)2 by H20 in dichloromethane is exothermic but entropically unfavorable due to the required reorganization of the solvent cage around released triflate ions. Thermodynamic parameters are also determined for OTf …

Characterization Of Polycyclic Aromatic Hydrocarbons (Pahs) By The Kinetics Of Depuration In Bivalve Molluscs, Mercenaria Mercenaria, C Sato, H Kim, John T. Tanacredi Ph.D.

Faculty Works: CERCOM

The objectives of this study were to examine depuration aspects of polycyclic aromatic hydrocarbons (PAHs) in a hard-shell clam Mercenaria mercenaria, and to characterize PAHs by the depuration kinetics. In this investigation, clams were exposed to artificial sea water containing a mixture of eight PAHs (i.e., naphthalene, fluorene, phenanthrene, flouranthene, pyrene, benz[a]anthracene, chrysene, benzo[a]pyrene) for 48 hours. The clams were then transferred into clean (PAH-free) artificial seawater for release, and sampled at predetermined intervals. The target PAHs were extracted from the clam tissue and quantified by a gas chromatograph equipped with a capillary glass column and FID.

The results …

Effect Of Phosphate On The Kinetics And Specificity Of Glycation Of Protein, Nancy G. Watkins, Carolyn I. Neglia-Fisher, Daniel G. Dyer, Suzanne R. Thorpe, John W. Baynes

Faculty Publications

The glycation (nonenzymatic glycosylation) of several proteins was studied in various buffiner os rder to assess the effects of buffering ions on the kinetics and specificity of glycation of protein. Incubation of RNase with glucose in phosphate buffer resulted in inactivation of the enzyme because of preferential modification of lysine residues ino r near the activsei te. In contrast, in the cationic buffers, 3-(N-morpholino)propanesulfonic acid and 3-(N-tris(hydroxymethyl)rnethylamino)- 2-hydroxypropanesulfonica cid, the kineticso f glycation of RNase were decreased 2- to 3-fold, there was a decrease in glycation of active site versus peripheral lysines, and the enzyme was resistant to inactivation by …

Determination Of Electrochemical Kinetic Parameters Using The Bond-Henderson-Oldham Global Analysis, Mark Anderson, Dennis Evans

Mark R. Anderson

No abstract is currently available.

Flow Injection Atomic Absorption Spectrometry: The Kinetics Of Instrument Response, J. M. H. Appleton, Julian Tyson

Chemistry Department Faculty Publication Series

The concept of dispersion coefficient is discussed with particular reference to flow injection atomic absorption spectrometry where the detector contributes appreciably to the analytical signal characteristics. Single- and parallel-tank models of instrument response are developed and critically examined. The progress made to date by investigators of nebuliser performance is briefly reviewed prior to developing a semi-empirical extended-tank model of instrument response. The capabilities of this model are explored by deriving a set of equations for instrument response, and comparing the predictions with experimental results. Agreement is generally good. Advantages of the modelling approach are discussed.

A Kinetic Study Pertaining To The Enzymatic Reduction Of Pyruvate By Lactate Dehydrogenase, Ronald Floyd Tienhaara

All Master's Theses

The reduction of pyruvate as catalyzed by lactate dehydrogenase has been studied by monitoring the oxidation of DPNH (diphosphopyridine nucleotide) at 340 nm. The kinetic investigation was carried out in phosphate buffer at 25° C. Since pyruvate exists in equilibrium with the enolized and hydrated forms, a kinetic analysis was devised to determine the nature of the true substrate for the enzymatic process. Also, a comparative study was made involving two isozymes of lactate dehydrogenase. The catalytic effectiveness of these isozymes was studied as a function of pH and substrate concentration.

The Kinetics And Mechanism Of The Reaction Of Molybdenum(V) With Iodine, Oxygen And Nitrate, Ervin Park Guymon

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Molybdenum compounds present a series of baffling chemical puzzles. By no means are all of these yet even clearly defined and many may never be. This complexity results from the ability of molybdenum to form six different oxidation states, which can possess three different coordination numbers. Furthermore, molybdenum compounds readily disproportionate to yield mixed valence compounds; and finally, molybdate ions readily aggregate in solution to form a variety of polyions by polymerization-condensation reactions which are controlled by pH and the concentration of the system. Molybdenum's complexity can best be summed up in the words of the late Edgar Smith who …