Determination Of Reaction Order Research Articles

Effect of α-Substitution on the Reactivity of C(sp3)-H Bonds in Pd0-Catalyzed C-H Arylation.

We report mechanistic studies on the reactivity of different α-substituted C(sp3)-H bonds, -CHnR (R = H, Me, CO2Me, CONMe2, OMe, and Ph, as well as the cyclopropyl and isopropyl derivatives -CH(CH2)2 and -CHMe2) in the context of Pd0-catalyzed C(sp3)-H arylation. Primary kinetic isotope effects, kH/kD, were determined experimentally for R = H (3.2) and Me (3.5), and these, along with the determination of reaction orders and computational studies, indicate rate-limiting C-H activation for all substituents except when R = CO2Me. This last result was confirmed experimentally (kH/kD ∼ 1). A reactivity scale for C(sp3)-H activation was then determined: CH2CO2Me > CH(CH2)2 ≥ CH2CONMe2 > CH3 ≫ CH2Ph > CH2Me > CH2OMe ≫ CHMe2. C-H activation involves AMLA/CMD transition states featuring intramolecular O → H-C H-bonding assisted by C-H → Pd agostic bonding. The "AMLA coefficient", χ, is introduced to quantify the energies associated with these interactions via natural bond orbital 2nd order perturbation theory analysis. Higher barriers correlate with lower χ values, which in turn signal a greater agostic interaction in the transition state. We believe that this reactivity scale and the underlying factors that determine this will be of use for future studies in transition-metal-catalyzed C(sp3)-H activation proceeding via the AMLA/CMD mechanism.

Comparison of Gravimetric Method with UV-Vis Spectrophotometry for Determination of Reaction Order in Natural Dyes Adsorption Process

The order of the reaction is the number of concentration factors that affect the speed of a chemical reaction. The reaction order can be used to determine how the adsorption process is in the colouring process based on determining the linear regression equation of the R square value. This study aims to compare the gravimetric method with the UV-Vis spectrophotometric method in determining the reaction order in chlorophyll samples of the natural dye papaya leaves. This study used a quantitative method to determine the value of the reaction order of the papaya leaf natural dye, with data analysis techniques including gravimetric method analysis to determine chlorophyll content, UV-Vis spectrophotometry to determine the value of chlorophyll absorbance and linear regression to determine the order of the reaction. The results showed that the two methods followed first order with an R-value of 0.951 for the gravimetric method and 0.994 for the UV-Vis spectrophotometric method. REFERENCESAisy, G. A. R. (2018). Analysis of the Chlorophyll Content of Papaya Leaf Extract (Upload Papaya L.) Against Extraction Time Variations Using a Hodothermal Extractor. Diponegoro University, (1969), 4–27.Azizah, H. P., & Utami, B. (2016). Utilization of Green Dyes from Papaya Leaves (Carica papaya L.) As a Natural Textile Dyes. UNY National Chemistry Seminar, (October 2016).Fauziah, L., & Wakidah, M. (2019). Extraction of Papaya Leaves (Carica papaya L.) Using Ultrasonic Cleaner. EKSAKTA: Journal of Sciences and Data Analysis, 19(1), 35–45.Khofya, A., & Aji, M. P. (2018). Papaya Leaf Extract (Upload Papaya L.) as a natural dye in batik cloth. Indonesian Journal of Natural Science Education (IJNSE), 1(1), 13–17.Manurung, M. (2012). Mangosteen Peel Application (Garcinia Mangostana L.) As a Natural Dyes on Cotton Fabrics by Pre-Mordanting. Journal of Chemistry, 6(2): 183-190.Matitaputty, J. K., Ufie, A., Ima, W., & Pattipeilohy, P. (2022). Implementation of Education for Sustainable Development (ESD) Through Ecopedagogy in Learning at SMP Negeri 8 Ambon. BUDIMAS Journal, 04(1). http://journal.um-surabaya.ac.id/index.php/JKM/article/view/2203Namirah, I., Affifah, I., Wijayanti, I. E., & Langitasari, I. (2019). Study of Natural Coloring Plants in the Outer Baduy Community. EduChemia (Journal of Chemistry and Education), 4(2), 204.Pujilestari, T. (2015). Review: Sources and Utilization of Natural Dyes for Industrial Purposes Dynamics of Crafts and Batik, 32(2), 93–106. Retrieved from https://media.neliti.com/media/publications/61575-ID-review-sumber-dan-pemanfaatan-zat-warna.pdfRibeiro, M. G. T. C., Costa, D. A., & Machado, A. A. S. C. (2010). “Green Star”: A holistic green chemistry metric for evaluation of teaching laboratory experiments. Green Chemistry Letters and Reviews, 3(2), 149–159.Saputra, B. W. (2008). Adsorption System. 6–21. Tugas Akhir Sarjana. Jurusan Teknik Elektro Universitas Indonesia, Jakarta.Sugiyono. (2011). Quantitative Research Methods, Qualitative and R&D. Bandung: Alphabet.

Kinetic Study of CaCO3 Precipitation Accelerated by High Voltage Impulse

Objectives : Determination of reaction order (n) and rate constants (k) of the CaCO<sub>3</sub> scale formation reaction that was accelerated by the HVI (high voltage impulse) induction.Methods : HVI was inducted to the synthetic solution containing 2.5 mM of Ca<sup>2+</sup> ion at different temperatures of 25, 40, 60℃. The concentration of Ca<sup>2+</sup> ion has been monitored as voltages of the HVI increased from 0 to 5, 10, 15 kV. Reaction order and the rate constants of the CaCO<sub>3</sub> formation reaction were determined with the experimental dataset of Ca<sup>2+</sup> concentration vs. time plots.Results and Discussion : The CaCO<sub>3</sub> formation was determined to follow two-molecules 2<sup>nd</sup> order reaction. The reaction rate constant, k increased as temperature and the applied voltages of HVI increased. The rate constant, k at 25℃ and 15 kV of HVI was 8.2×10<sup>-3</sup> L/(mmol･hr), which was 2.7 times greater than the k of the control at 25℃, 3.0×10<sup>-3</sup> L/(mmol･hr).Conclusions : The reaction of CaCO<sub>3</sub> formation was accelerated by HVI as the applied voltages of HVI increased, indicating that the HVI could be used as an alternative desalting technology for scale control.

Tuning smaller Co3O4 nanoparticles onto HZSM-5 zeolite via complexing agents for boosting toluene oxidation performance

Tunable smaller Co3O4 nanoparticles onto HZSM-5 zeolites were prepared by the addition of various rich-hydroxyl complexing agents. The physicochemical properties including the crystalline size, surface dispersion, reducibility and acidity of Co3O4 active component and the catalytic performance for toluene oxidation were extensively investigated by numerous characterization techniques and catalytic experiments. It was found that the smaller particle size and the better dispersion of Co3O4 nanoparticles on HZSM-5 zeolite after complexing agents addition lead to remarkable reducibility enhancement and higher abundance of surface acidity, which were proved to be the key factors for the elevation of toluene oxidation activity. Among all, the catalyst with β-cyclodextrin as the complexing agent (designated as Co3O4/HZSM-5/β-CD) exhibited not only the optimum catalytic activity, but also high catalytic stability under dry condition and good regeneration capacity under humid conditions. Based on the results of reaction order determination, a first-order reaction rate equation with respect to toluene concentration was derived under rich-oxygen atmospheres, which was in good accordance with the conclusion in previous research.

Catalytic oxidative transformation of betulin to its valuable oxo-derivatives over gold supported catalysts: Effect of support nature

Liquid-phase oxidation of betulin extracted from birch bark was studied over gold catalysts supported on a range of supports (hydrotalcite, ZrO2, ZnO, MgO, CeO2, La2O3, HMS and various alumina) with different morphology and properties. Gold catalysts as well as the corresponding supports were characterized by XRD, BET, ICP-OES, XPS and TEM. It was found that the nature of the support plays a decisive role in betulin oxidation over gold-based catalysts, expressed in the influence on the average size and distribution of gold nanoparticles and, thereby, on their catalytic performance (activity and selectivity) in betulin oxidation. Moreover, it was revealed that betulin oxidation catalyzed by gold is a structure sensitive reaction, requiring an optimal size of gold nanoparticles of ca. 3.3 nm. The most suitable support for gold was found to be alumina. Kinetic studies allowed determination of reaction orders and conditions favorable for selective formation of a particular oxo-derivative of betulin (betulone, betulinic and betulonic aldehydes, betulinic acid).

Кинетика сорбции нефти материалом на основе листового опада

Studies of leaf litter as a sorption material with respect to oil at various temperatures have been carried out. It has been revealed that with process temperature increasing, the samples sorption capacity decreases. The oil sorption mechanism has been studied. It has been shown that the active sorption time was in the interval from 60 to 600 seconds. It has been proved that at the time of oil and sorption material contact for more than 600 seconds, the desorption process began. Kinetic dependencies of oil absorption by the proposed sorption material have been constructed and analyzed. The reaction order determination by a graphic method has showed that obtained functions with a high degree of correlation can be attributed to first-order heterogeneous reactions. Have been calculated thermodynamic parameters confirming the absence of a chemical reaction between oil and leaf litter. The carried out researches determine the most acceptable parameters of oil sorption by material based on leaf litter.

Kinetics of photocatalytic, self-cleaning surfaces: A decision tree approach for determination of reaction order

Self-cleaning photocatalytic surfaces have several decades of application, yet satisfactory rate equations for analyzing the kinetics of reactions on such solid surfaces are lacking, due in large part to the many configurations of the catalyst and the deposited contaminants.We analyze the existing literature and show that nearly all studies can be described by application of the power law for rate of reaction:Rate = kcat [C] nwhere n = apparent reaction order, and kcat is a fundamental constant of the catalytic material. The value of reaction order, n, we show requires answers to the following six questions. In each case, the observed apparent kinetic order depends upon interplay among the distributions of photocatalyst, reactant, and irradiance.1. Is the photocatalyst porous or non-porous?Example: Stearic acid on/within non-porous/porous photocatalyst layer.2. Is the photocatalytically active layer optically thin or thick?Example: Dye conversion in TiO2 layers vs. 10% TiO2/SiO2?3. Is the probe reactant deposit a submonolayer or multilayer?Examples: Dye sub/multilayers with TiO24. Is probe reactant light absorption negligible or important?Example: Stearic acid vs. soot5. Is the probe reactant present as a continuous film or as a distribution of discrete islands?Example: Long chain carboxylic acids on TiO26. If distributed, what is breadth of distribution?Example: Stearic acid on TiO2For contaminant removal we demonstrate apparent reaction orders of 0, ½, 1, and 2! Simple analysis is used to explain this diversity of apparent reaction orders. We use the six questions posed to construct a decision tree for determination of the apparent reaction order, n, as a function of responses to the six questions.

Determination of reaction orders for ascorbic acid degradation during sterilization using a new experimental device: The thermoresistometer Mastia®

Sterilization is the most relevant technique to guaranty safety of shelf-stable highly hydrated food products at ambient temperature. However, these thermal processes are often optimised to microbiological aspect and consequently are not without consequences on food quality. Ascorbic acid's degradation at sterilization temperature (>100 °C) is poorly documented. Using a new instrumented reactor (thermoresistometer Mastia®), the behavior of ascorbic acid was studied in food model solution at pH = 3.5, in aerobic and anaerobic conditions from 95 °C to 125 °C. In anaerobic conditions, degradation was slow and followed first order kinetics (k125°C = 2.88*10−3 min−1, Ea = 96 kJ/mol). In aerobic conditions, reactions were faster with total elimination of ascorbic acid in about 4 h, and the data were best fitted using 0.5-order, while reaction speed varied little with temperature.

Leaching of Mersin/Aydincik dolomite ore in hydrochloric acid. dissolution rates

In this paper dissolution of dolomite ore, collected from Mersin/Aydincik in Turkey, was investigated at various experimental conditions in the presence of HCl acid. Particle size, acid/dolomite ratio, solid/liquid ratio, stirring speed, reaction time and temperature were also conducted to the determin the optimum experimental conditions. During the experiment, CO2 amount released from the dolomite was measured through the experimental apparatus so as to the determination of reaction orders and rate constants of the sample at the different temperatures by using the fractional life approach method. It was found that, reaction orders and rate constants, based on temperatures, changed from 1.505 to 1.339 and between 3.17 and 10.49 10 -2 mol dm -3 sec -1 respectively. In addition, differences in reaction rate constants were examined with Arrhenius equation and the activation energy of the dissolution process was calculated as 16.69 kJ mol -1 , which was consistent with the activation energies determined in literature.

Rapid determination of reaction order and rate constants of an imine synthesis reaction using a mesoscale oscillatory baffled reactor

The reaction of benzaldehyde with n-butylamine to form the imine (1-butanamine, N-(phenylmethylene)) was chosen to demonstrate the ability of the mesoscale OBRs to rapidly screen process conditions and obtain kinetic data in both continuous “multi-steady state” and “dynamic screening” manner. The two methods give ∼98% degree of agreement, with clear step-changes between different residence times. In situ FTIR spectroscopy was used to determine concentrations in real time. The results showed that the average rate constant was 2.0×10−1±0.006mol−0.9L0.9s−1 with about ∼1.0% different between the methods. In determining such kinetic information, the meso-OBR was able to reduce the process development time by about 50% of, and required 75% less reagent, compared to batch screening using standard beaker. Furthermore, the data was more reproducible with the average deviation three times lower across all the data points.

Kinetics of Methanol Steam Reforming with a Pd–Zn–Y/CeO2 Catalyst under Realistic Operating Conditions of a Portable Reformer in Fuel Cell Applications

Kinetics of methanol steam reforming (MSR) with a catalyst containing palladium and zinc on a cerium oxide support was investigated using a differential reactor approach. The goal of the study was to develop optimal process conditions for portable fuel reformers in fuel cell applications. Activation energies for the MSR reaction and for the overall methanol conversion, as well as pre-exponential factors and the reaction orders for CH3OH, H2O, H2, CO2, and CO were determined. The study covers the temperature range from 230 to 320 °C, consistent with the operation of a reformer integrated to a portable power fuel cell device. All work was done with a mixture of CH3OH and H2O with a volume ratio 2:1 (molar ratio 0.88:1) at atmospheric pressure, which is representative of the process conditions of practical interest for this application. For the determination of reaction orders the concentration of each reactant under consideration was varied to mimic a broad range of CH3OH conversions. The following power la...

Determination of reaction orders for the transesterification of canola oil with methanol by using KOH/MgO as a heterogeneous catalyst

The reaction orders with respect to the reactants were determined for the reaction of canola oil with methanol catalyzed by KOH/MgO. The method of initial rates was used to determine the reaction rate. The experiments were carried out with different initial concentrations of methanol and canola oil. A very good correlation was found between the experimental and calculated reaction rates using the proposed equation. The reaction rate equations derived from Eley–Rideal and Langmuir–Hinshelwood mechanisms were discussed. As a result, the orders of reaction respect to both oil and methanol are concordant with the suggestion that the reaction takes place both homogeneously and heterogeneously.

Rate parameter estimation for 4-chlorophenol degradation by UV and organic oxidants

The main objective of this study was to evaluate the rate parameters of degradation/mineralization of 4-chlorophenol (4-CP) using organic oxidants, viz., peroxy acetic acid (PAA), para nitro benzoic acid (PNBA), and methyl ethyl ketone peroxide (MEKP), in basic media, in combination with UV irradiation at 254 nm. All the experiments were conducted with varying time intervals, under identical conditions of UV irradiation and pH. The reactions were followed by HPLC analysis for residual concentration and GC–MS for mineralization, and intermediates/product identification. In the present investigation, the residual concentration data of 4-CP against time were analyzed for reaction order determination by differential and integral methods. The differential method yielded fractional order of reaction for all organic oxidants under consideration. Initially the profile was observed to be linear in the time span of 0–45 s for all the organic oxidants used and thus, first-order approximation was applied. The curvilinear path, which followed up till 300 s, was approximated to first-order and second-order kinetics. No noteworthy results were observed for pseudo-first order rate equation. The change in the nature of the curves was attributed to the formation of intermediates/reaction products.

Simultaneous determination of reaction order and rate constant by rank annihilation factor analysis from kinetic-spectral data

Rank annihilation factor analysis combined with the optimization of kinetic parameter is adopted to resolve the two-way kinetic-spectral data measured online from chemical reactions. To a multi-step reaction whose intermediate process is complicated and reaction order is fractional, the reaction order and rate constant of the first step can be determined without the knowledge of the kinetic model of the reaction. Taken a three-step reaction as an example, the synthetic data has been resolved and its effectiveness was proved. When the approach is applied to the analysis of practical reaction systems such as alkaline hydrolysis of phenyl benzoate, oxidization of sodium bromide by potassium permanganate and electro-degradation of sunset yellow, reliable results are obtained.

A novel reactor system for high throughput catalyst testing under realistic conditions

This article describes a 16-channel reactor system specifically designed for the high throughput study of supported heterogeneous catalysts under well controlled conditions. Each of the individual channels of the reactor has been designed to operate as an autonomous plug flow reactor without thermal or product cross-talk often associated with other reactors specifically designed for high throughput experimentation (HTE) studies. The flowrate difference between reactors was kept to a minimum through the use of orifices, and the temperature of each channel is continuously monitored. This level of control allows for the measurement of kinetically significant parameters in a high throughput manner. The system is also capable of studying transients occurring on the order of seconds, to further assist in kinetic analysis and understanding. Results are shown for the determination of reaction order during carbon monoxide oxidation over various supported metal catalysts measured under differential conversion.

Oxygen evolution at RuO 2( x)+Co 3O 4(1− x) electrodes from acid solution

A systematic investigation of the mechanistic and electrocatalytic properties of O 2 evolution from acidic solutions was conducted using Ti/RuO 2( x)+Co 3O 4(1− x) anodes prepared by thermal decomposition (470°C), with x varied between 0 and 100% mol. Kinetics were studied by current-potential curves recorded under quasi-stationary conditions and reaction order determination. At low overpotentials, a Tafel slope of about 30 mV was found for materials having a 30–80% mol RuO 2 content. A reaction mechanism has been proposed accounting for the composition dependence of the Tafel slope and the order of reaction at constant potential. It has been concluded that mixed oxides bring about an increase in the real electrocatalytic activity, which can be attributed to the synergetic or edge effect between the oxide components. A mechanism for the anodic dissolution of Co 3O 4 is proposed.

Oxygen evolution electrocatalysis in alkaline medium at thin Mn xCo 3- xO4 (0 ≤ x ≤ 1) spinel films on glass / SnO 2: F prepared by spray pyrolysis

Films of a series of manganese-cobalt mixed valency spinel oxides of theoretical formula Mn xCo 3-xO 4, (x = 0; 0.25; 0.5; 0.75 and 1), have been prepared by spray pyrolysis at 150 °C on conductive glass in order to relate solid state and surface chemistry to electrocatalytical activity towards the oxygen evolution reaction (OER). X-ray diffraction (XRD) and IR spectroscopy characterized their bulk crystalline properties. Both techniques have confirmed that all oxides belong to the spinel family. Their surface properties were characterized by XPS yielding the Co 3+ / Co 2+ surface ratio. The kinetics of the OER was investigated in 1 M KOH by means of steady state current-potential curves, obtained in the potentiostatic mode and by reaction order determination. The order of reaction ranging from 1.0 to 1.2, and the Tafel slopes ranging from 67 to 69 mV dec −1 can be tentatively interpreted by a mechanism involving a Temkin type of electrosorption of OH intermediates associated with an electrochemical rate-determining step. Replacing progressively Co by Mn, the electrodes were increasingly electrocatalytically less active, surface Co 3+ ions being the active sites, and making Co 3O 4 the most active in the series.

Estimation of kinetic rate parameters for coal combustion from measurements of the ignition temperature

Combustion reactivity plays a significant role in the development of optimal strategies for the efficient utilization of coal. A promising technique for characterization of combustion reactivity involves measurement of the gas temperatures which lead to the ignition of coal particles of different sizes, and the use of classical ignition theory to extract the relevant reaction rate parameters. This paper examines the influence of the modeling assumptions, within the framework of heterogeneous ignition theory, on the combustion rate parameters calculated from experimental data. It is shown that unequivocal determination of reaction order from ignition data is difficult. Further, the manner in which the rate constant is defined—whether it is based on the external or the internal surface area—exerts a significant influence on the reactivity parameters. The effect of radiation is included in the energy balance and shown to influence the results substantially, for larger particles in particular. Finally, it is shown that combustion reactivity determined from ignition measurements does not differ significantly from other measurement techniques if the effects of radiation and mass transport limitations are accounted for.

Application of regression transformations to the determination of reaction orders in stability studies

Box–Cox and link function transformations can assist in the determination of reaction orders in pharmaceutical studies.

Electrocatalytic properties of ternary oxide mixtures of composition Ru0.3Ti(0.7−x)CexO2: oxygen evolution from acidic solution

Mixed oxide electrodes of general composition Ru0.3Ti(0.7−x)Ce x O2 were prepared by thermal decomposition of the respective chlorides using Ti as a support. x was varied between 0 and 70 mol %. Oxygen evolution was used as a model reaction to investigate the dependence of the electrocatalytic properties on oxide composition. Kinetics was studied by quasistationary current-potential curves and reaction order determination. A minimum Tafel slope of about 30 mV has been found in the 10–30% CeO2 composition range. On the basis of a zero reaction order at constant overpotential, a reaction mechanism has been proposed accounting for the composition dependence of the Tafel slope. It has been concluded that the replacement of TiO2 with CeO2 brings about an increase in the electrocatalytic activity for oxygen evolution, while the layer becomes more prone to mechanical erosion.