Kinetic Study of the Reactions of Some 5-Nitro-2-(4-nitrophenoxy)-3-X-thiophenes with Aniline and 4-Methoxyaniline in Methanol

1999 ◽  
Vol 64 (11) ◽  
pp. 1877-1892 ◽  
Author(s):  
Vincenzo Frenna ◽  
Gabriella Macaluso ◽  
Giovanni Consiglio ◽  
Susanna Guernelli ◽  
Domenico Spinelli
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Kinetic Constant ◽  
Second Order ◽  
Base Catalysis ◽  
Monotonic Function ◽  
Order Kinetic ◽  
General Acid

The rate constants of the title reactions have been measured at various amine concentrations. The second-order kinetic constant for the amino substitution increases in a hyperbolic way as a function of the nucleophile concentration. The k3Am/k-1 ratio for each catalysed system is not a monotonic function of the X substituent. This result has been rationalized in the framework of the SB-GA (Specific Base-General Acid) mechanism of base catalysis.

scholarly journals Kinetic and Thermodynamic Studies of Chromium (VI) Sorption by Pure and Carbonized Fluted Pumpkin waste biomass (Telfairia occidentalis Hook F.)

2012 ◽  
Vol 27 ◽  
pp. 11-18
Author(s):  
Timi Tarawou ◽  
Michael Horsfall
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Industrial Effluents ◽  
Second Order ◽  
Order Kinetic ◽  
Waste Biomass ◽  
Fluted Pumpkin ◽  
Chromium Vi ◽  
Telfairia Occidentalis ◽  
Pseudo Second Order

The adsorption of chromium (VI) ions from aqueous solution was studied using pure and carbonized fluted pumpkin waste biomass (FPWB). The kinetic data shows a pseudo-first-order mechanism with rate constants of 1.26 × 10-2 and 1.933 × 10-2 mg g-1 min-1 for the pure and carbonized FPWB, respectively. While the pseudo-second-order mechanism has rate constants of 0.93 × 10-1 and 1.33 × 10-1 mg g-1 min-1 for the pure and carbonized waste biomass respectively. The pseudo-second order kinetic model was found to be more suitable for describing the experimental data based on the correlation coefficient values (R2) of 0.9975 and 0.9994 obtained for pure waste biomass (PWB) and carbonized waste biomass (CWB), respectively. The results obtained from this study show that PWB and CWB have very high removal capacity for chromium (VI) from aqueous solution over a range of reaction conditions. Thus, fluted pumpkin waste biomass (Telfairia occidentalis Hook F) is a potential sorbent for the treatment of industrial effluents containing chromium (VI) contaminant.DOI: http://dx.doi.org/10.3126/jncs.v27i1.6436 J. Nepal Chem. Soc., Vol. 27, 2011 11-18Uploaded date: 16 July, 2012

scholarly journals KINETICS OF OZONE REACTIONS WITH ADENINE AND CYTOSINE IN AQUEOUS SOLUTIONS

2020 ◽  
Vol 63 (10) ◽  
pp. 17-22
Author(s):  
Aigul A. Maksyutova ◽  
Elvina R. Khaynasova ◽  
Yuriy S. Zimin
Keyword(s):  
Aqueous Solutions ◽  
Rate Constants ◽  
Correlation Coefficients ◽  
Activation Parameters ◽  
Second Order ◽  
Order Kinetic ◽  
Temperature Dependences ◽  
Ozone Reactivity ◽  
Kinetics Of ◽  
Ozone Reactions

The ultraviolet spectroscopy method has been applied to study the kinetics of the ozone reactions with nitrogenous bases (NB), namely adenine and cytosine in aqueous solutions. At the first research stage, the range of NB working concentrations has been determined. It was found that linear dependences between optical densities and concentrations of nitrogenous bases aqueous solutions are quite reliable, with correlation coefficients r ≥ 0.998, are satisfied up to [NB] = 2.3 ∙ 10–4 mol/l. According to the Bouguer-Lambert-Beer law, adenine and cytosine extinction coefficients in aqueous solutions were determined and subsequently used to calculate their residual concentrations. At the next stage, the kinetics of nitrogenous bases ozonized oxidation was studied with equal initial concentrations of the starting substances ([NB]0 = [О3]0). The results revealed that the kinetic consumption curves of the starting reagents are fairly well linearized (r ≥ 0.996) in the second-order reaction equation coordinates. As found with the bubbling installation, 1 mol of the absorbed ozone falls on 1 mol of the used NB. Thus, the reactions of ozone with adenine and cytosine explicitly proceed according to the second-order kinetic laws (the first – according to О3 and the first – according to NB). The rate constants were calculated by the integral reaction equations, the values of which indicate a higher ozone reactivity in relation to nitrogen bases. The temperature dependences of the second-order rate constants was studied ranging 285-309 K, and the activation parameters (pre-exponential factors and activation energies) of the ozone reactions with adenine and cytosine in aqueous solutions were determined.

scholarly journals Kinetic Study of Photocatalytic Degradation of Tolonium Chloride Under High Pressure Irradiation in Aquatic Buffer Systems

2011 ◽  
Vol 8 (s1) ◽  
pp. S19-S26 ◽  
Author(s):  
M. Montazerozohori ◽  
S. Nezami ◽  
S. Mojahedi
Keyword(s):  
High Pressure ◽  
Photocatalytic Degradation ◽  
Kinetic Study ◽  
Rate Constants ◽  
Order Kinetic ◽  
Optimum Conditions ◽  
First Order ◽  
Reactor Cell ◽  
Order Kinetic Model ◽  
Tolonium Chloride

Anatase titanium dioxide catalyzed photodegradation of tolonium chloride at various bufferic pH of 2, 7, 9 and 12 in aqueous solution is presented. The effect of some physicochemical parameters such as initial concentration of dye, catalyst amount and reaction time on photocatalytic degradation has been investigated in a photo-reactor cell containing high pressure mercury lamp to obtain the optimum conditions in each bufferic pH at constant temperature. A complete spectrophotometric kinetic study of tolonium chloride under high pressure irradiation at buffer media was performed. The photocatalytic degradation observed rate constants (kobs) were found to be 2.90×10-3, 3.30×10-3, 3.20×10-3and 5.20×10-3min-1for buffer pH of 2-12 respectively. It was found that a pseudo-first-order kinetic model based on Langmuir-Hinshelwood one is usable to photodegradation of this compound at all considered buffer pH. In addition to these, the Langmuir-Hinshelwood rate constants, krfor the titled compound at various pH are reported.

Comparison of the biodegradability of the grey fraction of municipal solid waste of Barcelona in mesophilic and thermophilic conditions

2003 ◽  
Vol 48 (4) ◽  
pp. 21-28 ◽  
Author(s):  
S. Mace ◽  
D. Bolzonella ◽  
F. Cecchi ◽  
J. Mata-Alvarez
Keyword(s):  
Kinetic Study ◽  
Methane Production ◽  
Kinetic Constant ◽  
Order Kinetic ◽  
Organic Loading ◽  
First Order ◽  
Loading Rates ◽  
Start Up ◽  
Constant Operation ◽  
Thermophilic Conditions

The results of the start-up of two digesters in mesophilic and thermophilic conditions, together with its steady results at several organic loading rates are described. A kinetic study is also carried out which allows one to estimate the ultimate methane production, together with the first-order kinetic constant. Operation at thermophilic temperature yields better results as it allows a more loaded reactor and the methane production is slightly higher.

Kinetic Study on Oxidation of Thiodipropionic Acid by Iron (III)- bipyridine Complex

2016 ◽  
Vol 15 (2) ◽  
pp. 33-44
Author(s):  
John K Adaikalasamy ◽  
Selva A Priya ◽  
Sunaja K R Devi
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Second Order ◽  
Aqueous Acetonitrile ◽  
Order Rate ◽  
Uv Visible

Iron(III)-bipyridine complex was prepared andcharacterized by UV-Visible spectrophotometer. Kineticstudy was carried out by using this iron(III)-bipyridinewith thiodipropionic acid in aqueous acetonitrile solution.The reaction was optimized by studying the effect onsubstrate, solvent, oxidant, acidity and temperature. Firstorder, second order rate constants and activationparameters were calculated. The above reaction wasfound to be second order and proceeded through electrontransfer from thiodipropionic acid to iron(III)-bipyridinecomplex. The product was characterized and confirmedby IR and NMR spectroscopy.Keywords: Thiodipropionic acid, Iron(III)-bipyridine complex,kinetic study of Iron(III)-bipyridyl complexes.

Correlation pKa – activité catalytique des thiols dans la réaction d'hydrolyse de l'acétate de p-nitrophényle

1984 ◽  
Vol 62 (11) ◽  
pp. 2330-2336 ◽  
Author(s):  
Alain Brembilla ◽  
Denis Roizard ◽  
Jacqueline Schoenleber ◽  
Pierre Lochon
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Second Order ◽  
Species Comparison ◽  
Order Rate ◽  
Thiolate Anion ◽  
Group A ◽  
Hydrolysis Of

The kinetic study of the hydrolysis of p-nitrophenylacetate in the presence of primary thiols indicates the thiolate anion as the sole catalytic species. Comparison of the true second order rate constants (kRS−) reveals that purely aliphatic primary thiols behave differently from aromatic α-substituted primary thiols. In the latter group a correlation can be established between the true second order rate constants and the pKSH values by means of the Brönsted equation log kRS− = βpKSH + C, with β equal to 0.40 and C equal to −0.85.

Thermal Activation of Brazilian Smectite Clay (Primavera) and its Application for the Removal of Cadmium from Aqueous Solution

2020 ◽  
Vol 07 ◽  
Author(s):  
Marta Lígia Pereira da Silva ◽  
Tellys Lins Almeida Barbosa ◽  
Meiry Gláucia Freire Rodrigues
Keyword(s):  
Aqueous Solution ◽  
Kinetic Constant ◽  
Second Order ◽  
Order Kinetic ◽  
Experimental Conditions ◽  
X Ray ◽  
Thermally Activated ◽  
Study Results ◽  
Water Cleaning ◽  
Pseudo Second Order

Background: Region-based solutions for water cleaning could be critical to tackle the water challenges faced in enhancing the in the future. Brazilian Primavera clay is cheap, abundant, and an untested material that has the potential to be used for water cleaning. Objective: the objective of the present work was to thermally activate and characterize the Brazilian clay and then determine the potential to remove Cd2+ from an aqueous solution. Methods: Primavera clay was thermally activated at 300 oC and characterized using X ray diffraction, X-ray Spectroscopy Energy Dispersive, and N2 adsorption. Sorption equilibrium was determined using the following experimental conditions: constant pH 4.5, 5 h, and 27 oC. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms models were applied in order to determine the efficiency of clay used as an adsorbent. Adsorption kinetics was analyzed using the pseudo-second-order kinetic model. Results: In this study, results revealed that even though the heat treatment did not cause profound alterations on the clay structure(smectite) and surface area (78 m2 /g), a pseudo-second-order kinetic constant of 0.5563 mg/g/min was found for the cadmium removal. Conclusion: The mathematical models of the Langmuir and Temkin showed a better fit to the experimental data. A high affinity between the cadmium and the thermally activated Primavera clay was found up to 88 % with removal efficiencies.

scholarly journals Kinetic and High-Pressure Mechanistic Investigation of the Aqua Substitution in the Trans-Aquaoxotetracyano Complexes of Re(V) and Tc(V): Some Implications for Nuclear Medicine

2008 ◽  
Vol 2008 ◽  
pp. 1-9 ◽  
Author(s):  
J. Mattheus Botha ◽  
Andreas Roodt
Keyword(s):  
High Pressure ◽  
Nuclear Medicine ◽  
Kinetic Study ◽  
Rate Constants ◽  
Formation Rate ◽  
Activation Parameters ◽  
Second Order ◽  
Associative Mechanism ◽  
Mechanistic Investigation

A kinetic study of the aqua substitution in the [TcO(OH2)(CN)4]− complex by different thiourea ligands (TU = thiourea, NMTU = N-methyl thiourea, NNDMTU = N, N′-dimethylthiourea) yielded second-order formation rate constants (25∘C) as follows [NNDMTU, NMTU, TU, respectively]: kf = 11.5 ± 0.1, 11.38 ± 0.04, and 7.4 ± 0.1 M−1s−1, with activation parameters: ΔHkf#:55±2, 42±3, 35±5 kJ mol−1; ΔSkf#:−40±8, −84±11, −110±17 J K−1mol−1. A subsequent high-pressure investigation of the aqua substitution in the [ReO(OH2)(CN)4]− and [TcO(OH2)(CN4)]− complexes by selected entering ligands yielded ΔVkf# values as follows: Re(V): −1.7±0.3(NCS−), −22.1±0.9 (TU) and for Tc(V): −3.5±0.3(NCS−), −14±1 (NNDMTU), and−6.0±0.5 (TU) cm3mol−1, respectively. These results point to an interchange associative mechanism for the negative NCS− as entering group but even a pure associative mechanism for the neutral thiourea ligands.

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