Kinetics and Mechanistic Study on the Reaction of Iodo(diethylenetriamine) Platinum(II) with L-Cystine

2009 ◽  
Vol 62 (5) ◽  
pp. 493 ◽  
Author(s):  
Trilochan Swain ◽  
Prakash Mohanty
Keyword(s):  
Rate Constant ◽  
Total Concentration ◽  
Formation Rate ◽  
Activation Parameters ◽  
Order Rate Constant ◽  
Product Formation ◽  
Ring Closure ◽  
Mechanistic Study ◽  
Rescue Agent ◽  
Product Formation Rate

Substitution reactions of the complex [Pt(dien)I]+, where dien = diethylenetriamine or 1,5-diamino-3-azapentane, with the sulfur-containing rescue agent l-cystine have been studied in a 1.0 × 10–1 mol dm–3 aqueous perchlorate medium at various temperatures (25–50°C) and pH (2.30–1.00) using a UV-visible spectrophotometer. The products were characterized by their infrared and 1H NMR data at various temperatures. These data indicate that [Pt(dien)I]+ formed a complex with l-cystine through Pt–S bonds at pH 1.00–2.30. This Pt–S bond is observed at 50°C with ring closure of the dien (δ 3.8–3.9, 2H, CH2) and with open-ring dien (δ 3.2, 3.6–3.8 (dien), 2H, CH2). All reactions follow the rate law –d[mixture]/dt = (k1 + k2[Nu])[PtII], where k2 denotes a second-order rate constant and [Nu] is the total concentration of nucleophile. The product formation rate constant and activation parameters Ea, ΔH#, and ΔS# have been determined.

Improved Dynamic System of Microbial Continuous Fermentation and its Parameter Identification

2014 ◽  
Vol 633-634 ◽  
pp. 545-549
Author(s):  
Hong Li Xiao ◽  
Lan Zhang Chong ◽  
Fei Li Hang ◽  
Wang Yong
Keyword(s):  
Dynamic System ◽  
Consumption Rate ◽  
Continuous Fermentation ◽  
Formation Rate ◽  
Product Formation ◽  
Cellular Growth ◽  
Specific Substrate ◽  
Substrate Consumption ◽  
Specific Product ◽  
Product Formation Rate

In this paper, the nonlinear dynamic system of microbe continuous fermentation products 1,3-propanediol (1,3-PD) is rewritten by improving the specific cellular growth rate, specific substrate consumption rate and specific product formation rate. Firstly, under the condition of substrate glycol excess and active trans-membrane transport, according to the dynamic behavior the fermentation process, we consider the glycerol and 1,3–PD concentration within the cell, and improve the specific cellular growth rate, specific substrate consumption rate and specific product formation rate, then rewrite the dynamic system of microbial continuous fermentation process. Secondly, taking the dynamic system as main constraint condition, we establish the parameter identification model and prove the existence of the optimal solution. Lastly, the numerical results calculated by particle swarm algorithm show that the improved model is suitable for describe the dynamic behavior of 1,3-PD, but is not accurate enough for by-products.

scholarly journals Asymmetric Whole-Cell Bio-Reductions of (R)-Carvone Using Optimized Ene Reductases

Molecules ◽  
2019 ◽  
Vol 24 (14) ◽  
pp. 2550 ◽  
Author(s):  
Christoph Mähler ◽  
Christian Burger ◽  
Franziska Kratzl ◽  
Dirk Weuster-Botz ◽  
Kathrin Castiglione
Keyword(s):  
Formation Rate ◽  
Product Formation ◽  
Regeneration System ◽  
Initial Product ◽  
Whole Cell ◽  
Stirred Tank Reactors ◽  
E Coli ◽  
Space Time Yield ◽  
Product Formation Rate ◽  
Site Selective

(2R,5R)-dihydrocarvone is an industrially applied building block that can be synthesized by site-selective and stereo-selective C=C bond bio-reduction of (R)-carvone. Escherichia coli (E. coli) cells overexpressing an ene reductase from Nostoc sp. PCC7120 (NostocER1) in combination with a cosubstrate regeneration system proved to be very effective biocatalysts for this reaction. However, the industrial applicability of biocatalysts is strongly linked to the catalysts’ activity. Since the cell-internal NADH concentrations are around 20-fold higher than the NADPH concentrations, we produced E. coli cells where the NADPH-preferring NostocER1 was exchanged with three different NADH-accepting NostocER1 mutants. These E. coli whole-cell biocatalysts were used in batch operated stirred-tank reactors on a 0.7 l-scale for the reduction of 300 mM (R)-carvone. 287 mM (2R,5R)-dihydrocarvone were formed within 5 h with a diasteromeric excess of 95.4% and a yield of 95.6%. Thus, the whole-cell biocatalysts were strongly improved by using NADH-accepting enzymes, resulting in an up to 2.1-fold increased initial product formation rate leading to a 1.8-fold increased space-time yield when compared to literature.

Effect of Organometallic Compounds on the Formation of Carbon Nanostructures by Pulsed Electric Discharge of Fluorine-Containing Organic Liquid between Metal Electrodes

2010 ◽  
Vol 459 ◽  
pp. 67-70
Author(s):  
Katsuhiko Hosoi ◽  
Shin-ichi Kuroda
Keyword(s):  
Raman Spectrum ◽  
Electric Discharge ◽  
Carbon Nanostructures ◽  
Organic Liquid ◽  
Formation Rate ◽  
Organometallic Compounds ◽  
Product Formation ◽  
Metal Electrodes ◽  
Carbon Nanoparticle ◽  
Product Formation Rate

The carbon nanotube and carbon nanoparticle that contain fluorine on their surfaces were prepared by a pulsed electric discharge in a fluorine-containing organic liquid. The dominant product was nanoparticles with the diameters of ca. 5–100 nm in all experiments, however, the intensity ratio of G-band (1580 cm-1) to D-band (1350 cm-1) of the Raman spectrum of the products increased by addition of a catalyst indicating the formation of crystalline particles. The product formation rate also increased to 39.3 mg/A•s with ferrocene and 79.4 mg/A•s with nickelocene while with no catalyst it resulted in 12.5 mg/A•s.

scholarly journals Mitigation of pretreatment-derived inhibitors during lignocellulosic ethanol fermentation using spent grain as a nitrogen source

2021 ◽  
Author(s):  
Michael Persson ◽  
Mats Galbe ◽  
Ola Wallberg
Keyword(s):  
Cell Growth ◽  
Protein Hydrolysate ◽  
Formation Rate ◽  
Product Formation ◽  
Negative Effects ◽  
Porcine Pancreas ◽  
Nutrient Sources ◽  
Ethanol Formation ◽  
Spent Grain ◽  
Product Formation Rate

AbstractNitrogen-containing nutrient sources can be used to mitigate the negative effects of pretreatment-derived inhibitors on product formation rates during bioethanol production. Process economic limitations require these nutrients to be inexpensive. A method of hydrolyzing the protein in the spent grain fraction remaining after wheat grain saccharification, using porcine pancreas trypsin, is presented. This protein hydrolysate was shown to increase the volumetric productivity of ethanol production, measured after 24 h, during fermentation of a lignocellulosic hydrolysate from 0.24 to 0.60 g/L h. Although the effects on the productivity, on a per gram basis, were lower than with yeast extract, which increased the product formation rate to 1.64 g/L h, amino acid analysis of the soluble polypeptides in the protein hydrolysate showed that the feasibility of using spent grain as a nutrient source could be increased through optimization of the hydrolysis step. Furthermore, it was shown that pretreatment-derived inhibitors could reduce cell growth without affecting ethanol formation rates and that nutrient addition could increase ethanol formation rates without increasing cell growth. Finally, it was shown that the ability of nutrients to affect the product formation rate was limited above a certain inhibitor concentration.

Highly efficient hydroxylation of gaseous alkanes at reduced temperature catalyzed by cytochrome P450BM3 assisted by decoy molecules

2015 ◽  
Vol 19 (01-03) ◽  
pp. 329-334 ◽  
Author(s):  
Norifumi Kawakami ◽  
Zhiqi Cong ◽  
Osami Shoji ◽  
Yoshihito Watanabe
Keyword(s):  
Reaction Temperature ◽  
Consumption Rate ◽  
Formation Rate ◽  
Coupling Efficiency ◽  
Product Formation ◽  
Alkane Hydroxylase ◽  
Highly Efficient ◽  
Perfluorocarboxylic Acids ◽  
Product Formation Rate ◽  
Reduced Temperature

Cytochrome P450BM3 functions as a small-alkane hydroxylase upon the addition of perfluorocarboxylic acids (PFs) as decoy molecules. The coupling efficiency (product formation rate per NADPH consumption rate) for the hydroxylation of small alkanes was improved by reducing the reaction temperature to 0°C.

Effect of Flow Pulsations in Premixed, Swirl Stabilized Combustor

2014 ◽  
Author(s):  
Aayush K. Sharma ◽  
Uddalok Sen ◽  
Pallab Sinha Mahapatra ◽  
Swarnendu Sen ◽  
Achintya Mukhopadhyay
Keyword(s):  
Numerical Model ◽  
Gas Turbine ◽  
Formation Rate ◽  
Combustion Process ◽  
Product Formation ◽  
Primary Objective ◽  
Gas Turbine Combustor ◽  
Ansys Fluent ◽  
Thermoacoustic Instabilities ◽  
Product Formation Rate

In the present work, a numerical model has been developed using ANSYS Fluent 14.5 to simulate the combustion phenomenon in a partially premixed, swirl-stabilized, LPG-fueled gas turbine combustor. In a practical gas turbine combustor, pulsations in the flow at the air side cannot be avoided which can lead to thermoacoustic instabilities. The primary objective of the study is to numerically analyze the effect of such pulsations on the fluid flow and combustion process inside the combustor. Different parameters like static temperature, progress variable and product formation rate are compared at the outlet plane of the combustor. The effect of change in the parameters like amplitude and frequency of the sinusoidal air flow input has also been investigated in the present study. It is observed that the solution changes from periodic to quasi-periodic at a higher amplitude condition. The numerical model was qualitatively validated against experiments performed on a laboratory-scale premixed, swirl-stabilized, gas turbine combustor.

scholarly journals Kinetics and Mechanism of Oxidation of L-Ascorbic Acid by Pt(IV)(aq) in Aqueous Hydrochloric Acid Medium

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Sadhana Senapati ◽  
S. P. Das ◽  
A. K. Patnaik
Keyword(s):  
Electron Transfer ◽  
Ascorbic Acid ◽  
Acid Medium ◽  
Redox Reaction ◽  
Transfer Reaction ◽  
Total Concentration ◽  
Activation Parameters ◽  
Order Rate Constant ◽  
Electron Transfer Reaction ◽  
Reaction Products

Reduction of [PtCl6]2− by L-ascorbic acid (H2ASc) in 0.1 M aqueous acid medium has been investigated spectrophotometrically under pseudo-first order condition at [PtCl6]2− = 0.005–0.007 mol dm−3, 0.05 ≤ [H2ASc]/mol dm−3 ≤ 0.3, 298 K ≤ T ≤ 308 K, [H+] = 0.14 mol dm−3, I=0.5 mol dm−3. The redox reaction follows the rate law: d[Pt(IV)]/dt = k[H2ASc][Pt(IV)], where k is the second-order rate constant and [H2ASc] is the total concentration of ascorbic acid. Electron transfer from [H2ASc] to Pt(IV) center leading to the release of two halide ions and formation of the reaction products, square planner Pt(II) halide complex, and dehydrated ascorbic acid is suggested. This redox reaction follows an outersphere mechanism as Pt(IV) complex is substituted inert. Activation parameters were calculated corresponding to rate of electron transfer reaction k. Activation parameters favor the electron transfer reaction.

Unraveling the Mechanism of Tricyclic Bis-spiroketal Formation from Diyne Diol by DFT Study

2019 ◽  
Vol 16 (5) ◽  
pp. 392-395
Author(s):  
Kamlesh Sharma
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Dft Calculations ◽  
Density Functional ◽  
Activation Parameters ◽  
Product Formation ◽  
Ring Closure ◽  
Reaction Pathways ◽  
Enol Ether ◽  
Functional Theory

The mechanism of addition of nucleophiles to the π-acid complexed alkynes has been studied successfully by the assessment of energy of intermediates and activation parameters. To elucidate the origin of stereoselectivity and predict the reaction pathways, the geometry optimizations of reactants, products, intermediates and transition states, were calculated by using density functional theory (DFT) at the B3LYP/6-31+G(d) method. The reaction mechanism of hydration of alkynes in the catalyzed synthesis of bis-spiroketal by DFT calculations is explored. The pyranyl enol ether was formed regioselectively by the first ring closure. Further, bis-enol ether was formed by second 6-exodig addition. Then, dehydration, followed by dehydrative ring closure finally gave bis-spiroketal product. It is concluded that one of the most feasible reaction pathways comprises pyranyl enol ether and bis-enol ether formation as intermediates. The final cyclization step of product formation is endothermic. In terms of stereochemistry, the trans-product is found to be energetically more stable than cisproduct and hence supports the electivity of the reaction.

The kinetics of O2(aq) reduction during oxidative weathering of naturally occurring fracture minerals in groundwater

2003 ◽  
Vol 67 (2) ◽  
pp. 399-414 ◽  
Author(s):  
J. Rivas-Perez ◽  
E.-L. Tullborg ◽  
S. A. Banwart
Keyword(s):  
Rate Constant ◽  
Spent Nuclear Fuel ◽  
Total Concentration ◽  
Order Rate Constant ◽  
Second Order ◽  
Surface Complexes ◽  
Field Station ◽  
Naturally Occurring ◽  
Groundwater Environment ◽  
Reduction Capacity

Aqueous chemistry methods assessed the kinetic reactivity and reduction capacity of fracture-filling minerals from a granitic groundwater environment at the Aspo Hard Rock Laboratory, a field station for research and development into the geological disposal of spent nuclear fuel. Naturally occurring fracture filling reacted with oxygenated test solutions of known composition in recirculating batch reactors.The loss of O2(aq) with time was consistent with second-order reaction kinetics where O2(aq) is consumed through reduction by reaction with structural Fe(II) at the surface of the fracture minerals. Values of the second-order rate constant (k, l mole—1 h—1) varied between experiments within the range 1.7 < log k < 2.9 and values for the total concentration of reducing sites as a measure of the reduction capacity of the mineral (St, mole g—1) varied within the range 8.5 x 10—5 < St < 4.3 x 10—4. Values for the rate constant are somewhat less than those published previously for reaction between O2(aq) and Fe(II) surface complexes; i.e. structural Fe(II) appears to be less reactive than adsorbed Fe(II)(aq) but is significantly more reactive than Fe2+.Values of the rate constant did not depend on release of network ions from the reacting minerals, and did not vary significantly with pH, mineral mass, specific surface area or mineral Fe(II) content. Oxidative weathering of sulphide minerals does not occur to any measurable extent. When corrected to rock/water ratios for granite aquifers, the rate constants correspond to a half-life for O2(aq) on the order of seconds indicating an essentially instantaneous reaction on repository time scales. Comparison of reducing capacity for the fracture fillings and oxidizing capacity for groundwater saturated with O2(aq) indicates that oxidizing fronts within the geological barrier would travel ~4000 times more slowly than the velocity of groundwater flow.

scholarly journals Kinetic and Mechanistic Study of the Reduction of Chromium(VI) by Lactic Acid

2008 ◽  
Vol 2008 ◽  
pp. 1-4 ◽  
Author(s):  
Jinhuan Shan ◽  
Fang Wang ◽  
Changying Song ◽  
Heye Wang
Keyword(s):  
Lactic Acid ◽  
Rate Constant ◽  
Activation Parameters ◽  
Mechanistic Study ◽  
First Order ◽  
Chromium Vi ◽  
Rate Determining Step ◽  
Probable Reaction Mechanism ◽  
Probable Reaction ◽  
Aqueous Acidic Medium

The kinetics and mechanism of the reduction of chromium(VI) by lactic acid (Lac) in aqueous acidic medium was studied with spectrophotometry in a temperature range of 298.15 K~313.15 K. Under the conditions of the pseudo-first order , the observed rate constant increased with the increase in [Lac] and . There is no salt effect. Based on the experimental results, a probable reaction mechanism of oxidation was proposed. The rate equation derived from the mechanism could explain all the experimental phenomena. Activation parameters along with rate constant of the rate-determining step have been evaluated.

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