• Bulletin of the Korean Chemical Society
• /
• v.30 no.7
• /
• pp.1579-1582
• /
• 2009

The reaction rates of 4-X-2,6-dinitrochlorobenzenes (X = $NO_2,\;CN,\;CF_3$) with Y-substituted pyridines (Y = 3-$OCH_3,\;H,\;3-CH_3,\;4-CH_3$) in methanol-acetonitrile mixtures were measured by conductometry at 25 ${^{\circ}C}$. It was observed that the rate constant increased in the order of X = 4-$NO_2\;>\;4-CN\;>\;4-CF_3$ and the rate constant also increased in the order of Y = 4-$CH_3\;>\;3-CH_3\;>\;H\;>\;3-OCH_3$. When the solvent composition was varied, the rate constant increased in order of MeCN > 50% MeOH > MeOH. The electrophilic catalysis by methanol may be ascribed to the formation of hydrogen bonds between alcoholic hydrogen and nitrogen of pyridines in ground state. Based on the transition parameters, ${\rho}_S,\;{\rho}_N,\;{\beta}_Y,\;{\rho}_{XY}$ and solvent effects, the reaction seems to proceed via $S_N$Ar-Ad.E mechanism. We also estimated the isokinetic solvent mixtures (${\rho}_{XY}$ = 0) based on cross-interaction constants, where the substituent effects of the substrate and nucleophile are compensated.

• Journal of the Korean Chemical Society
• /
• v.28 no.5
• /
• pp.335-341
• /
• 1984

Acetals of ${\alpha},{\beta}$-unsaturated aldehydes reacted readily with aryl bromides in the presence of palladium catalyst and triethylamine to form aryl conjugated enals. Acrolein diethyl acetal and methacrolein diethyl acetal were reacted with phenyl bromides with substituents such as methyl and isopropyl groups at $100^{\circ}C$. The reaction products yields except the reaction of o-bromotoluene with methacrolein diethyl acetal. The products were identified by proton nuclear magnetic resonance and infrared spectroscopy. In the reverse combination of reactants to prepare aliphatic 2,4-dienals in good yield of above 50%, 3-bromopropenal dimethyl acetal and (E)-3-bromo-2-methylpropenal diethyl acetal were used as vinylic halide reactants and 1-alkenes and ethyl acrylate as olefin reactants.

• Journal of the Korean Chemical Society
• /
• v.37 no.6
• /
• pp.555-561
• /
• 1993

Ultraviolet spectrophotometric investigation has been carried out on the system of iododestannylation iodine and tetramethyltin in methanol. The transient CT absorption spectrum can be observed and the subsequent disappearance of CT absorption spectrum was accompained by the cleavage of tetramethyltin with iodine. From there, the rate constants for the iododestannylation were determined at 10, 25 and 35$^{\circ}C$ up to 1600 bar and the reaction rates were increased with increasing temperature and pressure. From these rate constants, the values of the activation parameters (${\Delta}V^\neq,\;{\Delta}{\beta}^{\neq},\;{\Delta}H^{\neq},\;{\Delta}S^{\neq}\;and\;{\Delta}G^{\neq}$) were obtained. The activation volumes and activation compressibility coefficients were both negativity. The activation enthalpies were positive and activation entropies had large negative values. From these values discussed in terms of solvent structure variation of transition state and mechanism. From these results, it was found that the reaction is followed with $S_E2$ mechaenism and weakened $S_E2$ mechanism nature by increasing pressure.

• Membrane Journal
• /
• v.8 no.4
• /
• pp.210-219
• /
• 1998

Sulfonated poly(ether sulfone)(SPES) of various ion exchange capacity (IEC) was prepared by heterogeneous sulfonation with chlorosulfonic acid (CSA) to make hydrophilic ultrafiltration membrane for reducing fouling. The effects of CSA concentration, reaction temperature and reaction time has been investigated. The reaction was effective when the temperature is above 10$\circ$C and the CSA concentration is over 0.05 mol, although polymer chain has been significantly degraded. The substitution of sulfonic acid groups was characterized by FTIR and $^1$H-NMR. Transport properties and fouling test have been conducted to the modified SPES ultrafiltration rnembranrs by heterogeneors method. Membranes were obtained using DCM and PVP as a non-solvent and pore forming agent, respectively. Flux reduced and rejection increased with ion exchange capacity. Finger-like structure was disappeared and the thickness of top layer was increased. Dense membrane by non-solvent DCM and porous membrane by pore forming agent PVP was prepared. Fouling was reduced with increasing ion exchange capacity because of hydrophilicity.

• Animal Bioscience
• /
• v.34 no.12
• /
• pp.1995-2002
• /
• 2021

Objective: Detection of adulteration in processed meats is an important issue for some countries due to substitution of beef with a cheaper source of protein like poultry. In this study, the presence of chicken meat was investigated using real-time polymerase chain reaction (real-time PCR) and enzyme-linked immunosorbent assay (ELISA) techniques to verify adulteration of fermented sausage samples. Methods: A total of 60 commercial samples were collected from 20 establishments in three replicates including 10 fermented sausage manufacturers and 10 butchers to investigate the presence of chicken meat with the sequential use of real-time PCR and ELISA techniques. In addition, pH, moisture content, water activity and color values of the samples were determined. Results: Both real-time PCR and ELISA showed agreement on the presence or absence of chicken meat in 55 out of 60 fermented sausage samples and chicken meat was identified with both methods in 16 samples. Five samples produced inconsistent results for the presence of chicken meat in the first run. Nevertheless, the presence of chicken meat was verified with both methods when these samples were analyzed for the second time. In addition, the average physico-chemical values of the fermented sausage samples tested positive for chicken meat were not significantly different from some of those fermented sausage samples tested negative for the chicken meat. Conclusion: The sequential use of real-time PCR and ELISA techniques in fermented sausages could be beneficial for the government testing programs to eliminate false negatives for detection of adulteration with chicken meat. Furthermore, consumers should not rely on some of the quality cues including color to predict the adulteration of fermented sausages with chicken meat since there were no statistical differences among some of the samples tested positive and negative for chicken meat.

• Journal of Electrochemical Science and Technology
• /
• v.13 no.4
• /
• pp.497-503
• /
• 2022

Spinel ferrites (Ni_xFe_3-xO₄; x = 0.25, 0.5, 0.75 and 1.0) have been prepared at 550℃ by egg white auto-combustion route using egg white at 550℃ and characterized by physicochemical (TGA, IR, XRD, and SEM) and electrochemical (CV and Tafel polarization) techniques. The presence of characteristic vibration peaks in FT-IR and reflection planes in XRD spectra confirmed the formation of spinel ferrites. The prepared oxides were transformed into oxide film on glassy carbon electrodes by coating oxide powder ink using the nafion solution and investigated their electrocatalytic performance for OER in an alkaline solution. The cyclic voltammograms of the oxide electrode did not show any redox peaks in oxygen overpotential regions. The iR-free Tafel polarization curves exhibited two Tafel slopes (b₁ = 59-90 mV decade^-1 and b₂ = 92-124 mV decade^-1) in lower and higher over potential regions, respectively. Ni-substitution in oxide matrix significantly improved the electrocatalytic activity for oxygen evolution reaction. Based on the current density for OER, the 0.75 mol Ni-substituted oxide electrode was found to be the most active electrode among the prepared oxides and showed the highest value of apparent current density (~9 mA cm^-2 at 0.85 V) and lowest Tafel slope (59 mV decade^-1). The OER on oxide electrodes occurred via the formation of chemisorbed intermediate on the active sites of the oxide electrode and follow the second-order mechanism.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.5C
• /
• pp.199-206
• /
• 2009

This paper presents full scale model tests on the various types of model piles carried out to estimate the behavior of laterally loaded steel-concrete composite piles. Subgrade-reaction spring system was developed to simulate the reaction of ground in laboratory condition. In addition, lateral behavior of piles under working load condition was estimated using composite loading system, which is available for independent loading in vertical and horizontal direction. Steel-concrete composite piles showed higher efficiency in lateral resistance rather than drilled shaft made of reinforced concrete. The lateral resistance of composite pile was larger than the summation of steel pile and concrete pile due to the composite effect by steel casing. The effect of shear key or strength of concrete on the behavior of composite pile was examined. The substitution of reinforcing bar by steel casing was also investigated.

• Annals of Occupational and Environmental Medicine
• /
• v.35
• /
• pp.23.1-23.14
• /
• 2023

Background: Exposure to heavy metals is a public health concern worldwide. Previous studies on the association between heavy metal exposure and neurobehavioral functions in children have focused on single exposures and clinical manifestations. However, the present study evaluated the effects of heavy metal complex exposure on subclinical neurobehavioral function using a Korean Computerized Neurobehavior Test (KCNT). Methods: Urinary mercury, lead, cadmium analyses as well as symbol digit substitution (SDS) and choice reaction time (CRT) tests of the KCNT were conducted in children aged between 10 and 12 years. Reaction time and urinary heavy metal levels were analyzed using partial correlation, linear regression, Bayesian kernel machine regression (BKMR), the weighted quantile sum (WQS) regression and quantile G-computation analysis. Results: Participants of 203 SDS tests and 198 CRT tests were analyzed, excluding poor cooperation and inappropriate urine sample. Partial correlation analysis revealed no association between neurobehavioral function and exposure to individual heavy metals. The result of multiple linear regression shows significant positive association between urinary lead, mercury, and CRT. BMKR, WQS regression and quantile G-computation analysis showed a statistically significant positive association between complex urinary heavy metal concentrations, especially lead and mercury, and reaction time. Conclusions: Assuming complex exposures, urinary heavy metal concentrations showed a statistically significant positive association with CRT. These results suggest that heavy metal complex exposure during childhood should be evaluated and managed strictly.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.6
• /
• pp.1951-1956
• /
• 2011

A kinetic study is reported on nucleophilic substitution reactions of 4-nitrophenyl nicotinate 5 and isonicotinate 6 with alkali metal ethoxide EtOM (M = K, Na, and Li) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. Plots of pseudo-first-order rate constant $k_{obsd}$ vs. EtOM concentration exhibit upward curvature for the reactions of 5 and 6 with EtOK and EtONa but are almost linear for those with EtOLi. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constant for the reaction with dissociated $EtO^-$ and ion-paired EtOM, respectively) has shown that $k_{EtOK}$ ${\geq}$ $k_{EtONa}$ > $k_{EtO^-}$ but $k_{EtOLi}$ < $k_{EtO^-}$. It has been concluded that $K^+$ and $Na^+$ ions catalyze the reactions by increasing the electrophilicity of the carbonyl carbon atom through formation of a 4-membered cyclic transition state $TS_3$ or $TS_4$. However, $M^+$ ion catalysis has been found to be much less significant for the reactions of 5 and 6 than for the corresponding reactions of 4-nitrophenyl picolinate 4, which was reported to proceed through a 5-membered cyclic transition state $TS_2$. Although 5 and 6 are significantly more reactive than 4-nitrophenyl benzoate 3, the reactions of 5 and 6 result in smaller $k_{EtOK}/k_{EtO^-}$ ratios than those of 3. The electron-withdrawing ability of the nitrogen atom in the acyl moiety of 5 and 6 has been suggested to be responsible for the increase in reactivity and the decrease in the $k_{EtOK}/k_{EtO^-}$ ratio.

• Journal of Ginseng Research
• /
• v.35 no.4
• /
• pp.504-513
• /
• 2011

In order to develop a novel system for the discrimination of five ginseng cultivars (Panax ginseng Meyer), single nucleotide polymorphism (SNP) genotyping assays with real-time polymerase chain reaction were conducted. Nucleotide substitution in gDNA library clones of P. ginseng cv. Yunpoong was targeted for the SNP genotyping assay. From these SNP sites, a set of modified SNP specific fluorescence probes (PGP74, PGP110, and PGP130) and novel primer sets have been developed to distinguish among five ginseng cultivars. The combination of the SNP type of the five cultivars, Chungpoong, Yunpoong, Gopoong, Kumpoong, and Sunpoong, was identified as 'ATA', 'GCC', 'GTA', 'GCA', and 'ACC', respectively. This study represents the first report of the identification of ginseng cultivars by fluorescence probes. An SNP genotyping assay using fluorescence probes could prove useful for the identification of ginseng cultivars and ginseng seed management systems and guarantee the purity of ginseng seed.