• The Pure and Applied Mathematics
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• v.22 no.1
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• pp.75-90
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• 2015

In this paper the existence of global solutions of the parabolic cross-diffusion systems with cooperative reactions is obtained under certain conditions. The uniform boundedness of $W_{1,2}$ norms of the local maximal solution is obtained by using interpolation inequalities and comparison results on differential inequalities.

• Bulletin of the Korean Chemical Society
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• v.18 no.4
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• pp.390-394
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• 1997

Nucleophilic substitution reactions of 2-thiopheneethyl benzenesulfonates (2-TEB) and 3-thiopheneethyl benzenesulfonates (3-TEB) with anilines and N,N-dimethylanilines (DMA) are investigated in acetonitrile at 60.0 ℃. The cross-interaction constants ρxz determined for the reactions with anilines are large negative (- 0.50) which are comparable to those for the similar predominantly frontside-attack SN2 reactions of 1-phenylethyl (1-PEB), 2-phenylethyl (2-PEB) and cumyl benzenesulfonates. A large negative ρxz value (- 0.4∼- 0.8) is considered to provide a mechanistic criterion for the frontside-attack SN2 mechanism with a four-center transition state. In agreement with this proposal the kinetic isotope effects, kH/kD, involving deuterated aniline nucleophiles are all greater than one reflecting partial N-H(D) bond cleavage in the transition state. The MO theoretical reactant structures of 1-PEB, 2-PEB and 2-TEB based on the PM3 calculation show that the benzene ring blocks the backside nucleophile approach to the reaction center carbon (Cα) enforcing the frontside-attack SN2 mechanism.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.634-641
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• 1998

Quasiclassical trajectory calculations were carried out for the reactions of $H+H_2$ (V=O, J=O) and its isotope variants on the Siegbahn-Liu-Truhlar-Horowitz potential energy surface for the relative energies E between 6 and 150 kcal/mol. The goal of the work was to understand the inter- and intramolecular isotope effects. We examine the relative motion of reactants during the collision using the method of analysis that monitors the intermolecular properties (internuclear distances, geometry of reactants, and final product). As in other works, we find that the heavier the incoming atom is, the greater the reaction cross section is at the same collision energy. Using the method of analysis we prove that the intermolecular isotope effect is contributed mainly by differences in reorientation due to the different reduced masses. We show that above E=30 kcal/mol recrossing also contributes to the intermolecular isotope effect. For the intramolecular isotope effect in the reactions of H+HD and T+HD, we reach the same conclusions as in the systems of $O(^3P)+HD$, F+HD, and Cl+HD. That is, the intramolecular isotope effect below E=150 kcal/mol is contributed by reorientation, recrossing, and knockout type reactions.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.589-596
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• 2012

In this paper, the reactive dynamics properties of the reactions Ba + $C_6H_5Br$ and Ba + m-$C_6H_4CH_3Br$ were studied by means of the quasi-classical trajectory method based on the London-Eyring-Polanyi-Sato potential energy surfaces. The vibrational distributions, reaction cross sections, rotational alignments of the products BaBr all were obtained. The peak values of the vibrational distributions are located at $\nu$ = 0 for the reactions Ba + $C_6H_5Br$ and Ba + m-$C_6H_4CH_3Br$ when the collision energies are 1.09 and 1.10 eV, respectively. The reaction cross sections increase with the increasing collision energy, which changes from 0.6 to 1.5 eV. The product rotational alignments deviate from -0.5 and firstly increase and then decrease while the collision energy is increasing, just like that of Heavy+Light-Light system.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2635-2644
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• 2014

Gold-catalyzed tandem cyclization-oxidative alkynylation and cyclization-fluorination reactions of 2-alkynone O-methyloximes are described. The reactions proceed smoothly at room temperature in the presence of 10 mol % of $(PPh_3)AuNTf_2$, 2.5 equivalents of selectfluor, and 2 equivalents of $K_3PO_4$. 2-Alkynone O-methyloximes undergo intramolecular oxyauration/cyclization and ensuing oxidative cross-coupling and fluorination process to afford the corresponding 3,4,5-trisubstituted isoxazoles in a cascade manner.

• Bulletin of the Korean Chemical Society
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• v.9 no.3
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• pp.133-135
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• 1988

Kinetics and mechanism of the nucleophilic substitution reactions of phenacyl bromides with anilines in methanol-acetonitrile mixtures at $45.0^{\circ}C$ are reported. The reaction is found to proceed via $S_N2$ process, but the magnitudes of cross interaction constants, ${\rho}_{XY}$, between substituents X in the nucleophile and Y in substrate were unusually small, even after allowing for the fall off due to non-conjugative intervening -CO group in the reactant. As in the other phenacyl derivatives, the resonance shunt phenomenon was invoked to explain the remarkable diminuation of the $|{\rho}_{XY}|$ values.

• Bulletin of the Korean Chemical Society
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• v.10 no.5
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• pp.459-462
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• 1989

The transition state (TS) structure for the reactions of phenacyl benzenesulfonates with N,N-dimethylanilines (DMA) is investigated using various selectivity parameters, especially with cross-interaction constants, ${\rho}_{ij}$, ${\beta}_{ij}$ and ${\lambda}_{ij}$. The trends in reactivity were similar to aniline series but the TS was found to be somewhat looser than that for aniline series. It was found that the RSP and BEP principle hold within the DMA series but are violated between two different reaction series with DMA and aniline.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1244-1248
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• 1998

Ozonolysis reactions of cyclic olefins 1a-c and norbomene In in the presence of trifluoroactophenone 6 provided the corresponding cross-ozonides 7a-c and 7n. Further reactions of ozonides 7a-c and 7n with the independently prepared carbonyl oxide 11 gave diozonides of structure l0a-c and 10n. The ozonolysis of 1methylcyclopentene 12a and 1-methylcyclohexene 12b in the presence of trifluoroactophenone 6 provided exclusively ozonide 15 and 16 derived from capture of carbonyl oxide 13. All of the new ozonides have been isolated as pure substances and characterized by their 1H NMR and 13C NMR spectra.

• Bulletin of the Korean Chemical Society
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• v.19 no.12
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• pp.1334-1336
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• 1998

Kinetic studies are carried out on the reactions of 2-chloro-2-propen-1-yl arenesulfonates with anilines and N,N-dimethylanilines in acetonitrilile at 45.0 ℃. The 2-chloro substituent is found to deactive the allyl moiety with considerable decrease in the rates. The sign and magnitude of the cross-interaction constant (ρxz 0.3) and the inverse secondary kinetic isotope effect (kH/kD 0.92) support an SN2 mechanism with a relatively tight transition state. The possibility of an SN2' mechanism can be safely precluded based on the ρxz values observed.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1785-1788
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• 2010