• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3539-3543
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• 2012

Butacaine sulfate is an ester of p-aminobenzoic acid which has been widely used as a local anaesthetic and it is a long standing agent particularly for spinal anaesthesia. For this reason, a kinetic study of oxidation of butacaine sulfate by sodium N-chlorobenzenesulfonamide (chloramine-B or CAB) has been carried out in $HClO_4$ medium at 303 K in order to explore this redox system mechanistic chemistry. The rate shows a first-order dependence on both $[CAB]_o$, and $[substrate]_o$, and a fractional-order dependence on acid concentration. Decrease of dielectric constant of the medium, by adding methanol, increases the rate of the reaction. Variation of ionic strength and addition of benzenesulfonamide or NaCl have no significant effect on the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated. The stoichiometry of the reaction has been found to be 1:2 and the oxidation products have been identified by spectral analysis. The observed results have been explained by plausible mechanism and the related rate law has been deduced.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.383-393
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• 2020

The corrosion behavior of Hastelloy C-276 was investigated to identify its applicability for carbon-anode-based oxide reduction (OR), in which Cl₂ and O₂ are simultaneously evolved at the anode. Under a 30 mL·min^-1 Cl₂ + 170 mL·min^-1 Ar flow, the corrosion rate was less than 1 g·m^-2·h^-1 up to 500℃, whereas the rate increased exponentially from 500 to 700℃. The effects of the Cl₂-O₂ composition on the corrosion rate at flow rates of 30 mL·min^-1 Cl₂, 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂, and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂ with a constant 170 mL·min^-1 Ar flow rate at 600℃ was analyzed. Based on the data from an 8 h reaction, the fastest corrosion rate was observed for the 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂ case, followed by 30 mL·min^-1 Cl₂ and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂. The effects of the chlorine flow rate on the corrosion rate were negligible within the 5-30 mL·min^-1 range. A surface morphology analysis revealed the formation of vertical scratches in specimens that reacted under the Cl₂-O₂ mixed gas condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.462-469
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• 2012

Cr(VI)-4,4'-bipyridine complex(4,4'-bipyridinium dichromate) was synthesized by the reaction of 4,4'-bipyridine with chromium trioxide in H2O, and characterized by IR, ICP. The oxidation of benzyl alcohol using 4,4'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order: cyclohexene$CH_3$, H, m-Br, m-$NO_2$) smoothly in N,N'-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.63(303K). The observed experimental data have been rationalized as follows; the proton transfer occurs after the prior formation of a chromate ester in the rate determining step.

• Journal of the Korean Applied Science and Technology
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• v.15 no.4
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• pp.79-85
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• 1998

$Cu_xFe_{3-x}O_4$ catalyst and $Zn_xFe_{3-x}O_4$ catalyst were synthesized by the air oxidation method with various C(II) and Zn(II) weights. Activated catalysts decomposed carbon dioxide to carbon at $350^{\circ}C$, $380^{\circ}C$, $410^{\circ}C$ and $440^{\circ}C$. The value of carbon dioxide decomposition rate for $Cu_{0.003}Fe_{2.997}O_4$ and $Zn_{0.003}Fe_{2.997}O_4$ catslysts than was better catalysts. The decomposed rate of the catalysts is about 85%${\sim}$90%. The reaction rate constant(4.00 $psi^{1-{\alpha}}/min$) and activation energy(2.62 kcal/mole) of $Cu_{0.003}Fe_{2.997}O_4$ catalyst are better than $Zn_{0.003}Fe_{2.997}O_4$

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2929-2933
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• 2010

Pseudo-first-order rate constants ($k_{obsd}$) have been measured for nucleophilic substitution reactions of 2-pyridyl benzoate 5 with alkali metal ethoxides (EtOM, M = Li, Na, K) in anhydrous ethanol. The plots of $k_{obsd}$ vs. $[EtOM]_o$ are curved upwardly but linear in the excess presence of 18-crown-6-ether (18C6) with significant decreased $k_{obsd}$ values in the reaction with EtOK. The $k_{obsd}$ value for the reaction of 5 with a given EtONa concentration decreases steeply upon addition of 15-crown-5-ether (15C5) to the reaction medium up to ca. [15C5]/$[EtONa]_o$ = 1, and remains nearly constant thereafter, indicating that $M^+$ ions catalyze the reaction in the absence of the complexing agents. Dissection $k_{obsd}$ into $k_{EtO^-}$- and $k_{EtOM}$, i.e., the second-order rate constants for the reaction with the dissociated $EtO^-$ and the ion-paired EtOM, respectively has revealed that ion-paired EtOM is 3.2 - 4.6 times more reactive than dissociated $EtO^-$. It has been concluded that $M^+$ ions increase the electrophilicity of the reaction center through a 6-membered cyclic transition state. This idea has been examined from the corresponding reactions of 4-pyridyl benzoate 6, which cannot form such a 6-membered cyclic transition state.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.91-94
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• 2003

Kinetic studies of the reaction of O-methyl-S-phenylthiocarbonates with benzylamines in methanol at 45.0 ℃ have been carried out. The reaction proceeds by a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterionic tetrahedral intermediate, $T^{\pm}$, with a hydrogen-bonded four-center type transition state (TS). These mechanistic conclusions are drawn based on (ⅰ) the large magnitude of ${\rho}_X\;and\;{\rho}_Z$, (ⅱ) the normal kinetic isotope effects $(k_H/k_D\;>\;1.0)$ involving deuterated benzylamine nucleophiles, (ⅲ) the positive sign of ${\rho}_{XZ}$ and the larger magnitude of ${\rho}_{XZ}$ than that for normal $S_N2$ processes, and lastly (ⅳ) adherence to the reactivity-selectivity principle (RSP) in all cases.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.620-629
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• 2022

By varying various experimental conditions such as heating rate, molar hourly space velocity (MHSV), and nitridation reaction temperature, vanadium oxynitride was prepared through temperature programmed reduction/nitridation reaction (TPRN) of vanadium pentoxide and ammonia, and characterization were performed. In order to investigate the physico-chemical properties of the prepared catalyst, N₂ adsorption-desorption analysis, X-ray diffraction analysis (XRD), hydrogen temperature programmed reduction (H₂-TPR), temperature programmed oxidation (TPO), ammonia temperature programmed desorption (NH₃-TPD), transmission electron microscopy (TEM) was performed. Transformation of V₂O₅ with 5 m² g^-1 low specific surface area by reduction at 340 ℃ to V₂O₃ showed a high specific surface area value of 115 m² g^-1 by micropore formation. As the nitridation temperature increased beyond that, the specific surface area continued to decrease due to sintering. The nitridation reaction variable that had the greatest influence on the specific surface area was the reaction temperature, and the x + y value of VN_xO_y of a single phase approached from 1.5 to 1.0 as the nitridation reaction temperature increased. At a high reaction temperature of 680 ℃, the cubic lattice constant a was VN. close to the value. At 680 ℃, the highest nitridation temperature among the experimental conditions, the ammonia conversion rate was 93%, and no deactivation was observed.

• Journal of the Korean Institute of Gas
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• v.10 no.2 s.31
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• pp.1-6
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• 2006

In this study we proposed on effect of the photodecomcomposition of coated nanofiber by $Pd/TiO_2$ for the removal of formaldehyde gas as indoor air pollutant. The photocatalytic reactor was setup in the inside of rectangular box (volume 2 l), UV lamp and the coating nanofiber with $Pd/TiO_2$. This study investigated the reaction rate and the adsorption constant of Langmuir-Heinshelwood, conversion of formaldehyde gas on temperature ($40^{\circ}C{\sim}80^{\circ}C$), effect of conversion (%) under different concentration, and effect of conversion (%) with humidity level on added $SO_2$ gas. As results, the rate constant (k) and adsorption constant (ft) were 114.94ppmv/min, $0.0036ppmv^{-1}$, respectively. and the conversion (%) of formaldehyde gas on temperature ($40^{\circ}C{\sim}80^{\circ}C$) was decreased to about 24%, compare with the first conversion (%). In conversion effect of increasing humidity levels, the presence of sulfur dioxide further decreased than without sulfur dioxide. the decreasing reason of conversion with presence sulfur dioxide judged as a cause of interference factor on the decrease of contact chance with photocatalysts.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.999-1005
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• 2008

The main reaction for soil washing with using sodium hydroxide(NaOH) and hydrogen peroxide(H$_2$O$_2$) was desorption and flotation of petrochemical contaminant by means of oxygen bubble. We found the rate of decomposition by rate constant according to various temperature. For the purpose of optimizing the operation factor, we examined the effect of concentration of NaOH and H$_2$O$_2$, washing time, and soil:water ratio. The rate of decomposition for H$_2$O$_2$ in liquid phase is the first order reaction by its concentration. The rate constant of k$_1$ was 0.9439 $\times$ exp(-1376.82/RT) when concentration of NaOH was lower than 0.1 M, and the rate constant of k$_2$ was 17.3588 $\times$ exp(-2320.06/RT) when it was higher than NaOH of 0.1 M. It found that NaOH was facilitated at the beyond of specific concentration. We confirmed the optimum concentration of NaOH/H$_2$O$_2$ by means of rate constants during soil washing. Also, the optimum conditions during soil washing were washing time of 15 min, soil : water ratio of 1 : 3, and NaOH/H$_2$O$_2$ concentration of 0.25 M/0.1 M.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2438-2442
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• 2014

A kinetic study is reported for $S_NAr$ reaction of 1-fluoro-2,4-dinitrobenzene (5a) and 1-chloro-2,4-dinitrobenzene (5b) with alkali-metal ethoxides (EtOM, M = Li, Na, K and 18-crown-6-ether complexed K) in anhydrous ethanol. The second-order rate constant increases in the order $k_{EtOLi}$ < $k_{EtO^-}$ < $k_{EtONa}$ < $k_{EtOK}$ < $k_{EtOK/18C6}$ for the reaction of 5a and $k_{EtOLi}$ < $k_{EtONa}$ < $k_{EtO^-$ < $k_{EtOK}$ < $k_{EtOK/18C6}$ for that of 5b. This indicates that $M^+$ ion behaves as a catalyst or an inhibitor depending on the size of $M^+$ ion and the nature of the leaving group ($F^-$ vs. $Cl^-$). Substrate 5a is more reactive than 5b, although the $F^-$ in 5a is ca. $10pK_a$ units more basic than the $Cl^-$ in 5b, indicating that the reaction proceeds through a Meisenheimer complex in which expulsion of the leaving group occurs after the rate-determining step (RDS). $M^+$ ion would catalyze the reaction by increasing either the nucleofugality of the leaving group through a four-membered cyclic transition state or the electrophilicity of the reaction center through a ${\pi}$-complex. However, the enhanced nucleofugality would be ineffective for the current reaction, since expulsion of the leaving group occurs after the RDS. Thus, it has been concluded that $M^+$ ion catalyzes the reaction by increasing the electrophilicity of the reaction center through a ${\pi}$-complex between $M^+$ ion and the ${\pi}$-electrons in the benzene ring.