• Bulletin of the Korean Chemical Society
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• v.26 no.9
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• pp.1339-1343
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• 2005

The N-inversion energies and nucleophilic ring-opening reactions of N-substituted aziridine compounds are investigated using B3LYP/6-31+$G^*$ methods, where substituents (R) on the nitrogen atom has been H (1), Me (2), Ph (3), Bn (4), CHMePh (5), $CO_2Me$ (6), COPh (7) and $SO_2Ph$ (8). The N-inversion energy with X group are decreased as the following order: R = CHMePh (17.06 kcal/mol) $\gt$ Me (16.97) $\gt$ Bn (16.70) $\gt$ H (16.64) $\gt$ $SO_2Ph$ (12.18) $\gt$ Ph (8.91) $\gt$ COPh (5.75) $\gt$ $CO_2Me$ (5.48). For reactivity of the ring opening toward cyanide ion, the aziridine 6 (R=$CO_2Me$) is shown to be the most reactive one. During the ring opening of aziridine 6 by CN$^{\ominus}$, the torsional OCNC angle becomes near to $180^{\circ}$, where the geometry allows for the effective incorporation of electrons of the nitrogen atom to the C=O bond. It would be a possible driving force for nucleophilic ring opening reaction as well as decreasing the N-inversion energy barrier. Regarding to the regioselectivity, the orientation of nucleophile in ring opening reaction appears to be different in the case of 9 and 10. The results are discussed in terms of steric/electronic effect of the $C_2$-substituents.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3690-3694
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• 2013

The $H_2Ge=Ge:$ and its derivatives ($X_2Ge=Ge:$, X = H, Me, F, Cl, Br, Ph, Ar${\ldots}{\ldots}$) is a new species. Its cycloaddition reactions is a new area for the study of germylene chemistry. The mechanism of the cycloaddition reaction between singlet state Cl2Ge=Ge: and formaldehyde has been investigated with CCSD(T)//MP2/$6-31G^*$ method. From the potential energy profile, it could be predicted that the reaction has only one dominant reaction pathway. The reaction rule presented is that the two reactants first form a fourmembered Ge-heterocyclic ring germylene through the [2+2] cycloaddition reaction. Because of the 4p unoccupied orbital of Ge: atom in the four-membered Ge-heterocyclic ring germylene and the ${\pi}$ orbital of formaldehyde forming a ${\pi}{\rightarrow}p$ donor-acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with formaldehyde to form an intermediate. Because the Ge: atom in intermediate hybridizes to an $sp^3$ hybrid orbital after transition state, then, intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state. The research result indicates the laws of cycloaddition reaction between $H_2Ge=Ge:$ and formaldehyde, and laid the theory foundation of the cycloaddition reaction between $H_2Ge=Ge:$ and its derivatives ($X_2Ge=Ge:$, X = H, Me, F, Cl, Br, Ph, Ar${\ldots}{\ldots}$) and asymmetric ${\pi}$-bonded compounds, which is significant for the synthesis of small-ring and spiro-Ge-heterocyclic compounds. The study extends research area and enriches the research content of germylene chemistry.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.104-105
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• 2006

We succeeded the synthesis of new functional polymers by novel ring-opening addition reactions of bis(oxetane)s with diacyl chlorides, di(active ester)s, and di(carboxylic acid)s using quaternary onium salts as catalysts at appropriate conditions. Hyperbranched polyesters with many pendant hydroxy groups were also synthesized by the polyaddition of bis(oxetane)s with tricarboxylic acid, or by the self-polyadditions of $AB_2\;or\;A_2B$ type monomers containing oxetane group. The anionic ring-opening polymerization of (3-ethyl-3-hydroxymethyl)oxetane was examined using sodium tert-buthoxide to give hyperbranched poly(ether)s containing one oxetanyl group and many hydroxyl groups in the end of polymer chain.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2414-2418
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• 2007

N-Hydroxy diketopiperazine derivatives from L- and D-forms of Ser and Cys were synthesized for the first time and the ring conformation of both analogues in water was determined to be close to flat via NMR and ab initio calculations. However, the side chain of the Ser analogue was oriented toward a pseudo-equatorial position while that of the Cys analogue was slightly oriented toward a pseudo-axial direction, with a slightly distorted boat-shaped ring conformation. Among them, the D-Cys analogue was found to be a weak inhibitor of α- glucosidase.

• Bulletin of the Korean Mathematical Society
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• v.57 no.1
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• pp.117-126
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• 2020

Let R be a commutative ring with identity. A proper ideal I of R is called 2-prime if for all a, b ∈ R such that ab ∈ I, then either a² or b² lies in I. In this paper, we study 2-prime ideals which are generalization of prime ideals. Our study provides an analogous to the prime avoidance theorem and some applications of this theorem. Also, it is shown that if R is a PID, then the families of primary ideals and 2-prime ideals of R are identical. Moreover, a number of examples concerning 2-prime ideals are given. Finally, rings in which every 2-prime ideal is a prime ideal are investigated.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1911-1916
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• 2004

The conformational preference of tetrahomodioxacalix[4]arenes with three different para substituents on the phenolic ring has been investigated by using ab initio molecular orbital theory (RHF/6-31$G^{\ast}$) and density functional theory (B3LYP/6-31$G^{\ast}$). The stability order is predicted to be cone > C-1,2-alternate > partial cone > 1,3-alternate > COC-1,2-alternate. The distorted cone conformation is found to be most stable in a gas phase and the calculated results are in agreement with the reported $^1$H NMR and X-ray experimental observations. The substitution of methylene with dimethyleneoxa bridges increases the size of the annulus of the molecule, its conformational mobility, and the number of hydrogen bonding patterns. The thermodynamic stability and the conformational characteristics of tetrahomodioxacalix[4]arenes are discussed in regards of the number of phenolic hydrogen bonding patterns and the polarity of a molecule. The substituent effects on the para position of the phenolic ring are also introduced.

• Communications of the Korean Mathematical Society
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• v.39 no.1
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• pp.93-104
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• 2024

Let R be a commutative ring with identity. In this paper, we introduce a new class of ideals called the class of strongly quasi J-ideals lying properly between the class of J-ideals and the class of quasi J-ideals. A proper ideal I of R is called a strongly quasi J-ideal if, whenever a, b ∈ R and ab ∈ I, then a² ∈ I or b ∈ Jac(R). Firstly, we investigate some basic properties of strongly quasi J-ideals. Hence, we give the necessary and sufficient conditions for a ring R to contain a strongly quasi J-ideals. Many other results are given to disclose the relations between this new concept and others that already exist. Namely, the primary ideals, the prime ideals and the maximal ideals. Finally, we give an idea about some strongly quasi J-ideals of the quotient rings, the localization of rings, the polynomial rings and the trivial rings extensions.

• Kyungpook Mathematical Journal
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• v.51 no.3
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• pp.283-291
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• 2011

In this paper, a generalization of the class of semicommutative rings is investigated. A ring R is called central semicommutative if for any a, b ${\in}$ R, ab = 0 implies arb is a central element of R for each r ${\in}$ R. We prove that some results on semicommutative rings can be extended to central semicommutative rings for this general settings.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.158.1-158.1
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• 2003

We report here the results on N-acetyl-N"-methylamide of oxazolidine (Ac-Oxa-NHMe) calculated using the ab initio molecular orbital method with the self-consistent reaction field (SCRF) theory at the HF level of theory with the 6-31 +G(d) basis set. The displacement of the $\gamma$-$CH_2$ group in proline ring by oxygen atom has affected the structure of proline, cis-trans equilibrium, and rotational barrier. The up-puckered structure is found to be prevalent for the trans conformers of the Oxa amide. (omitted)

• Journal of the Korean Chemical Society
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• v.39 no.7
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• pp.493-500
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• 1995

The geometry optimization of oxazole, relevant to the binding of lexitropsin that contains this ring to the base pair (G-C sequence) of minor groove of DNA, is performed with the aid of MM+ and ab initio (Hartree-Fock) calculations. The proton affinity and electronic structure are calculated at the 6-31G and $6-31G^{\ast}$ level for the optimized geometry. The proton affinities are also studied for various substituted oxazoles with the electron-donating and -withdrawing groups to estimate the substituent effect on the proton affinities of oxazoles. It is shown that the electron-donating substituents increase the proton affinity of oxazole, while the electron-withdrawing substituents decrease it. This result can be explained with atomic charge and electron density at oxygen of substituted oxazoles.