• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5990-5996
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• 2011

6-Methylquinolinium dichromate[$(C_{10}H_9NH)_2Cr_2O_7$] was synthesized by the reaction of 6-methylquinoline with chromium trioxide in $H_2O$, and characterized by IR, ICP. The oxidation of benzyl alcohol using 6-methylquinolinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order: cyclohexene < chloroform < acetone < N,N- dimethylformamide. In the presence of hydrochloric acid($H_2SO_4$ solution), 6-methylquinolinium dichromate oxidized benzyl alcohol and its derivatives(p-$OCH_3$, m-$CH_3$, H, m-$OCH_3$, m-Cl, m-$NO_2$) smoothly in DMF. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.67(303K). The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.104-106
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• 1989

Halopyrimidines such as 2-chloro-, 5-bromo, and 4,6-dichloro-5-nitropyrimidine undergo substitution reactions with superoxide anion radical (superoxide) to give the corresponding hydroxypyrimidines under suitable conditions. Parallel experiments employing hydroxide instead of superoxide strongly indicate that the reactivity of superoxide is comparable to that of the hydroxide in the reaction with halopyrimidines. The results seem to provide a piece of information in favor of the nucleophilic substitution rather than electron-transfer mechanism in the title reaction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.221-226
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• 2013

The water soluble quantum dots (QDs) are synthesized by the phase transfer and silica coating reaction. The photoluminescence intensity of silica-coated QDs are mainly affected by the amount of phase transfer agent, SDS (sodium dodecyl sulfate), and the maximum value is obtained at the cmc (critical micell concentration) concentration of SDS in the phase transfer reaction. Based on fluorescence spectra and field emission transmission electron microscope (FETEM), the energy transfer rate by forster resonance energy transfer (FRET) is increasing with the thickness of the silica shell coated on CdSe/ZnS QDs.

• Bulletin of the Korean Chemical Society
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• v.17 no.10
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• pp.939-943
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• 1996

Reactions that proceed within mixed acetylene-methanol and ethylene-methanol cluster ions were studied using an electron-impact time-of-flight mass spectrometer. When acetylene and methanol seeded in helium are expanded and ionized by electron impact, the ion abundance ratio, [CH3OH+]/[CH2OH+] shows a propensity to increase as the acetylene/methanol mixing ratio increases, indicating that the initially ionized acetylene ion transfers its charge to adjacent methanol molecules within the clusters. Investigations on the relative cluster ion intensity distributions of [CH3OH2+]/[CH3OH+] and [(CH3OH)2H+]/[CH3OH·CH2OH+] under various experimental conditions suggest that hydrogen-atom abstraction reaction of acetylene molecule with CH3OH ion is responsible for the effective formation of CH2OH ion. In ethylene/methanol clusters, the intensity ratio of [CH3OH2]/[CH3OH] increases linearly as the relative concentration of methanol decreases. The prominent ion intensities of (CH3OH)mH over (CH3OH)m-1CH2OH ions (m=1, 2, and 3) at all mixing ratios are also interpreted as a consequence of hydrogen atom transfer reaction between C2H4 and CH3OH to produce the protonated methanol cluster ions.

• Bulletin of the Korean Chemical Society
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• v.11 no.6
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• pp.497-505
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• 1990

The function exp$(x^2)$erfc(x), which is often encountered in studies of electrode kinetics, is evaluated to an extended precision with 32 significant decimal digits in order to find theoretical relationships used in derivative polarography/voltammetry for a chemically-coupled electrode process. Computations with a lower precision are not successful. Evaluation of the function is accomplished by using three types of expansions for the function. Best ranges of arguments are selected for each equation for particular precisions for efficiencies. The method is successfully applied to calculate higher-order derivatives of the current-potential curves in all potential ranges for a reversible electron transfer reaction coupled with a prior chemical equilibrium (i.e., a CE type process). Various parameters that characterize the peak asymmetry (such as ratios of peak-heights, ratios of half-peak-widths, and separations in peak-potentials) are analyzed to find how kinetic and thermodynamic parameters influence shapes of the derivatives. The results from the CE process is compared with those from an EC process in which a reversible electron transfer is coupled with a follow-up homogeneous chemical reaction. The two processes exibit quite contrasting differences for values of the parameters.

• Bulletin of the Korean Chemical Society
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• v.26 no.12
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• pp.1953-1961
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• 2005

We have performed high-level quantum mechanical calculation for multiple proton transfer in HOCl + HCl and $H_2O$ + $ClONO_2$ on water clusters, which can be used as a model of the reactions on ice surface in stratospheric clouds. Multiple proton transfer on ice surface plays crucial role in these reactions. The structures of the clusters with 0-3 water molecules and the transition state structures for the multiple proton transfer have been calculated. The energies and barrier heights of the proton transfer were calculated at various levels of theory including multi-coefficient correlated quantum mechanical methods (MCCM) that have recently been developed. The transition state structures and the predicted reaction mechanism depend very much on the level of theory. In particular, the HF level can not correctly predict the TS structure and barrier heights, so the electron correlation should be considered appropriately.

• Journal of the Korean Chemical Society
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• v.27 no.3
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• pp.213-217
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• 1983

Devices that mimic the natural photosynthetic pathway are of considerable interest as fuel sources. Quantum yield of viologen radical formation in several water-in-oil microemulsion system were measured. The yield of hexadecylviologen radical formation in microemulsion system using EDTA as an electron donor, ruthenium bipyridinium complex as photosensitizer, and hexadecylviologen as an electron acceptor was 12%. When benzylnicotinamide was inserted in the interface of the microemulsion and azo compound was dissolved in oil face, the quantum yield of hydroazo compound was 0.16. Organic dye (Rose bengal) was used as photosensitizer for the photoinduced electron transfer reaction. In anionic microemulsion no electrontransfer was observed.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1108-1114
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• 2013

Photochemical reactions of fluoro- vs. nonfluoro-substituted polymethylenoxy chain linked phthalimide were carried out to explore how electronegative fluorine atoms inside the donor chain influence photocyclization reaction efficiencies and to briefly determine the alkali metal binding properties of the photoproducts. The results of this study show that the fluorine-substituted donor chain linked phthalimide undergoes inefficient photocyclization via single electron transfer (SET)-induced excited state pathways to generate 14-membered cyclic amidol compared to nonfluoro-analog due to low electron donor ability of the terminal oxygen donor site. These results show that photoinduced intramolecular SET processes arising from ${\alpha}$-silyl ether electron donors to phthalimides are largely dependent on the kinds of substituents inside donor chain. Finally, a preliminary study with the cyclic amidols generated in this effort showed that they have weak alkali metal cation binding properties regardless of absence/presence of fluoro-substituents.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1939-1944
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• 2011

The nucleophilic substitution reactions of bis(Y-aryl) chlorophosphates (1) with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at 35.0 $^{\circ}C$. The kinetic results of 1 are compared with those of Y-aryl phenyl chlorophosphates (2). The substrate 1 has one more identical substituent Y compared to substrate 2. The cross-interaction between Y and Y, due to additional substituent Y, is significant enough to result in the change of the sign of cross-interaction constant (CIC) from negative ${\rho}_{XY}$ = -1.31 (2) to positive ${\rho}_{XY}$ = +1.91 (1), indicating the change of reaction mechanism from a concerted $S_N2$ (2) to a stepwise mechanism with a rate-limiting leaving group departure from the intermediate (1). The deuterium kinetic isotope effects (DKIEs) involving deuterated anilines ($XC_6H_4ND_2$) show secondary inverse, $k_H/k_D$ = 0.61-0.87. The DKIEs invariably increase as substituent X changes from electron-donating to electron-withdrawing, while invariably decrease as substituent Y changes from electron-donating to electron-withdrawing. A stepwise mechanism with a rate-limiting bond breaking involving a predominant backside attack is proposed on the basis of positive sign of ${\rho}_{XY}$ and secondary inverse DKIEs.

• BMB Reports
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• v.31 no.5
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• pp.444-452
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• 1998

The visible spectra of soybean ferric leghemoglobin reductase exhibited a charge transfer band at 530 nm under aerobic condition. Spectra of the oxidized enzyme show a flavin peak at 454 nm and the enzyme has three redox states associated with the active site of the enzyme. The enzyme has an active disulfide bridge and two-electron transfer may dominate in the ferric state of leghemoglobin reduction. The midpoint potentials of the enzyme were determined by spectrotitration to be -0.294 V for disulfide/dithiol and -0.318 V for FAD/$FADH_2$. Since the midpoint potentials for $NAD^+$/NADH and the ferrous/ferric states of leghemoglobin are -0.32 V and +0.22 V, respectively, it is proposed that two electrons are transferred sequentially from NADH to FAD, to the disulfide group, and then to the ferric state of leghemoglobin in the enzyme reaction.