• Journal of the Korean Chemical Society
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• v.12 no.3
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• pp.89-92
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• 1968

A theoretical study was made on the energies of ${\pi}$ electrons and the reactivity of each atom of porphin nucleus and phthalocyanine nucleus in the ground states. The energy of each ${\pi}$ orbital, the superdelocalizabilities and the bond orders have been calculated by the simple Huckel method. With respect of these two compounds, results of the calculations have shown that the energy differences between highest occupied orbitals and lowest vacant orbitals are relatively less than those of other common organic compounds. This suggests that these two compounds will be easily excited. Then, by superdelocalizabilities and bond orders, the reactivities of electrophilic, nucleophilic and radical reactions and bond strenghs have been respectively considered.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.313-320
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• 1994

Rosin-maleic anhydride adduct(RMA) was synthesized from rosin and maleic anhydride. Highly purified RMA for the application of polymerization monomer was synthesized by means of two methods; the melt reaction followed by further purification and the solution reaction. As a result of this study, the solution reaction was better than the melt reaction for obtaining higher yield of RMA. Maximum yield of RMA obtained by the melt reaction was only 40%. But the yield of RMA obtained by the reaction in carbon tetrachloride solution was 48%(theoretical yield 87.6%) and that obtained by the reaction in acetic acid solution was 51.5%(theoretical yield 94%) respectively.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.38-44
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• 1985

Photoreaction path for the monocyanochromium (Ⅲ) ion was inferred from the experimentally observed product ratio and theoretical analysis. The angular overlap model was used to analyze the d-orbital of various intermediates along a selected reaction coordinate and to determine quartet state energy level. A loss of equatorial ammine leads to pentacoordinated square pyramid with CN- ligand in an equatorial position. The SP(CNeq) intermediate undergoes a rearrangement by the N-Cr-CN bending. This process leads to a trigonal bipyramidal intermediate in which the CN- ligand is located in equatorial position. The subsequent association with a solvent molecule should probably proceed by lateral attack an one edge of the equatorial triangle. The assumption adopted above was consistent with experimental results.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1934-1938
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• 2012

The reaction mechanism between cyclopropenylidene and formaldehyde has been systematically investigated employing the MP2/6-311+$G^*$ level of theory to better understand the cyclopropenylidene reactivity with carbonyl compound. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the potential energy surface have been calculated. Energies of all the species are further corrected by the CCSD(T)/6-311+$G^*$ single-point calculations. It was found that one important reaction intermediate (INTa) has been located firstly $via$ a transition state (TSa). After that, the common intermediate (INTb) for the two pathways (1) and (2) has been formed $via$ TSb. At last, two different products possessing three- and four-membered ring characters have been obtained through two possible reaction pathways. In the reaction pathway (1), a three-membered ring alkyne compound has been obtained. As for the reaction pathway (2), it is the formation of the four-membered ring conjugated diene compound. The energy barrier of the ratedetermining step of pathway (1) is lower than that of the pathway (2), and the ultima product of pathway (2) is more stable than that of the pathway (1).

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1998-2004
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• 2012

We carried out DFT calculations for monohydrated sulfuric and phosphoric acids. We are interested in clusters which differ in orientation of hydrogen atoms only. Such molecular complexes are close in energy, since they lie in the vicinity of the global minimum energy structure on the flat potential energy surface. For monohydrated sulfuric acid we identified four different isomers. The monohydrated phosphoric acid forms five different conformers. These systems are difficult to study from the theoretical point of view, since binding energy differences in several cases are very small. For each structure, we calculated harmonic vibrational frequencies to be sure that if the optimized structures are at the local or global minima on the potential energy surface. The analysis of calculated -OH vibrational frequencies is useful in interpretation of infrared photodissociation spectroscopy experiments. We employed four different DFT functionals in our calculations. For each structure, we calculated binding energies, thermodynamic properties, and harmonic vibrational frequencies. Our analysis clearly shows that DFT approach is suitable for studying monohydrated inorganic acids with different hydrogen atom orientations. We carried out MP2 calculations with aug-cc-pVDZ basis set for both monohydrated acids. MP2 results serve as a benchmark for DFT calculations.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.277-286
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• 2008

This paper deals with the theoretical derivation of the modified Haldane model of the substrate inhibition in the microbial growth processes. Based on the biological concepts of substrate-receptor complex working mechanisms, a new microbial kinetics of N-fold multiplex substrate inhibition and its generalization has been considered theoretically, which is natural expansion of the simple substrate inhibition mechanism in the enzyme reaction. As a result, the modified Haldane model of the substrate inhibition turns out to be a well-designed four-parameter kinetic model with a biological constant of the total substrate inhibition concentration.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2228-2234
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• 2010

Theoretical studies have been performed to study the binding characteristics of the alkali metal iodides, M-I (M = Li, Na, K), to poly(ethylene oxide) (PEO, I), poly(ethylene amine) (PEA, II) and poly(ethylene N-methylamine) (PEMA, III) via the B3LYP method. In this study, two types of complexes, singly-coordinated systems (SCS) and doubly-coordinated systems (DCS), were considered, and dissociation energies (${\Delta}E_D$) were calculated both with and without basis set superposition error (BSSE). Two types of counterpoise (CP) approach were investigated in this work, but the ${\Delta}E_D$ values corrected by using the function CP (fCP) correction exhibited an unusual trend in some cases due to deformation of the sub-units. This problem was solved by including geometry relaxation in the CP-corrected (GCP) interaction energy. On the other hand, the effects of the BSSE on the structures were very small when the complexes were re-optimized on the CP-corrected (RCP) potential energy surface (PES), even if the bond lengths between X and $M^+$ ($d_{{X-M}^+}$) and between $M^+$ and $I^-$ ($d_{M^+-I^-}$) were slightly lengthened. Therefore, neither the GCP nor RCP corrections made much difference to the dissociation energies.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1973-1976
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• 2008

Electronic photodepletion spectrum of dibenzo-18-crown-6 with a potassium ion ($K^+$-DB18C6) was obtained in the gas phase using electrospray ionization and quadrupole ion-trap reflectron time-of-flight mass spectrometry. The spectrum exhibited rather a broad absorption band at 36350 $cm^{-1}$, which was tentatively assigned as the origin of the S1 band. The photodepletion spectrum of $Cs^+$-DB18C6 was also obtained to elaborate the effects of metal cations on electronic and geometric structures of metal cation-DB18C6 complexes. We found that the S1 band of $Cs^+$-DB18C6 was red-shifted by 180 $cm^{-1}$ from that of $K^+$-DB18C6. With the results of quantum theoretical calculations using the density functional theory, we suggested that the red-shift arose mainly from weaker binding of $Cs^+$ to DB18C6 than that of K+, which resulted from a larger size of $Cs^+$ than that of the cavity in DB18C6.

• Analytical Science and Technology
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• v.18 no.4
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• pp.263-270
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• 2005

Nuclear track is an useful tool for elemental analysis of radionuclides, such as uranium, plutonium and thorium, etc., and for elements undergoing nuclear reactions with thermal neutrons such as lithium and boron. This method has various application fields such as detecting fissionable radionuelides, measuring the fission rate in nuclear technology, analyzing cosmic radiation from meteorite, calculating the age of minerals as well as their history, etc. Track registration method has been applied to the microscopic analysis of boron and fissionable element such as uranium in KAERI. This report reviews the theoretical background of the nuclear track formation, practical procedures to obtain etched tracks and a perspective of the future.

• Bulletin of the Korean Chemical Society
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• v.12 no.2
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• pp.214-219
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• 1991

To study the effect of solvents and counterions in Z-DNA crystal of d(5BrC-G-5BrC-G-5BrC-G), we performed the local energy analysis and then molecular dynamics simulations. Since counterions raise serious caging problems in crystal simulations, it is very important to search for the possible positions before simulations. For this purpose, the local energy analysis was done for the whole crystal volume. It is shown from our simulation that counterions along with water molecules play a bridging role to bind adjacent oligomers so as to form the crystal. In this crystal, each water molecule bound to Gua-N2H, either directly or indirectly, hydrates the adjacent anionic phosphate oxygen, and thus assists Gua to be in a syn position. From the simulation, the average root-mean-square deviation of allthe DNA heavy atom coordinates from the X-ray data is $0.99{\AA}$ . The bases are less deviated from the X-ray positions than the phosphates. The temperature factors from the simulation are consistent with those from the X-ray refinement, showing that the phosphates are more mobile than the bases.