• 대한화학회지
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• 제15권6호
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• pp.318-323
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• 1971

Reactions of trimethylsilyldiphenylphosphine with phenylisocyanate and ethylisocyanate were studied at various temperatures for 3 days. Trimethylsilyldiphenylphosphine gave cyclic dimer, cyclic trimer and diphenylcarbodiimide from phenylisocyanate, but gave cyclic trimer, triethylisocyanurate, only from ethylisocyanate. In these reactions, it is suggested that trimethylsilyldiphenylphosphine was used to be an effective catalyst for cyclization of isocyanates.

• 대한화학회지
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• 제16권5호
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• pp.284-289
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• 1972

벤질브로마이드와 여러가지 m-또는 p-핵치환 지오벤즈아미드류와의 반응속도를 전기전도도법으로 측정하였다. 이들 반응에서 전자흡인치환기는 반응속도를 촉진하였고 한편 전자공여치환기는 반응속도를 억제하였다. 이 사실에 부합하는 반응 메카니즘을 고찰하였다. 추가하여 이들 반응에 있어서의 활성화에너지와 활성화엔트로피를 산출하였다.

• Bulletin of the Korean Chemical Society
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• 제23권11호
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• pp.1553-1559
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• 2002

Calculations are presented for the molecule HC2N and its geometrical isomers. The structures, harmonic frequencies and dipole moments are reported. The potential energy surface of the [H,C,C,N] system is investigated in detail, and the transition states, intermediate complexes, and the energies of barrier for the isomerization and dissociation reactions are computed in order to determine the reaction paths and to estimate the stability of the isomers. The barriers of isomerization among HCCN, HCNC and HNCC are computed to be rather large and dissociations of these molecules are highly endothermic, indicating that these molecules are kinetically stable. The association reactions HC + CN→HCCN, HC + NC→HCNC, and HN + CC →HNCC are barrierless and very exothermic, suggesting that they may be considered as efficient means of producing the HCCN and the isomers in the laboratory and in interstellar space.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.291-294
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• 2002

The reactions of triplet oxygen atom with halomethanes as a potential fire extinguisher were studied by a discharge flow-chemiluminescence imaging method. The experiments were carried out under second order conditions. The bimolecular atom-molecule reaction rate constants were determined in terms of the initial rate method. The initial concentration of oxygen atom was also determined under second order rate law instead of the pseudo-first order conditions with $[O(^3P)]_0{\ll}[sample]_0$. The second order conditions were more reliable than pseudo-first order conditions for the determinations of rate constants. The rate constants of the reactions $CF_3I\;+\;O(^3P)$, $CH_3PI\;+\'O(^3P)$, and $CHBrCl_2\;+\;O(^3P)$ were determined to be $5.0\;{\times}\;10^{-12}$ , $1.1\;×\;0^{-11}$ , and $1.9\;{\times}\;10^{-14}cm^3molecule^{-1}s^{-1}$, respectively.

• 생약학회지
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• 제25권1호
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• pp.35-40
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• 1994

Aqueous extreact of fresh ginseng (AFG) was examined for the antigenicity in Hartley guinea pigs in comparision with ovalbumin (OVA). When guinea pigs were sensitized with AFG emulsified with complete Freund's adjuvant (CFA), these animals showed negative reactions in active systemic anaphylaxis (ASA), active cutaneous anaphylaxis (ACA) and passive cutaneous anaphylaxis (PCA) tests and passive hemagglutination (PHA) reaction. On the contrary, when guinea pigs were sensitized with OVA emulsified with CFA as positive controls, these animals disclosed positive reactions in ASA, ACA and PCA tests and PHA reaction. From these results, AFG was considered not to possess antigenic properties in guinea pigs. In addition, the dose levels of AFG empolyed in the present experiment were confirmed not to suppress immune reactions.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2381-2386
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• 2009

The tetrakis(thio)-substituted-1,4-benzoquinone products 4a-e, 6, 7, and the mono(alkoxy)-tris(thio)-substituted-1,4- benzoquinone products 5a-e and 8a-e were synthesized from the reactions of p-chloranil with some thiols and mixture of two different thiol compounds in alcohol in the presence of $Na_2CO_3$ at room temperature. The structures of the novel S,S,S,S- and S,S,S,O- substituted products, which were obtained by the reactions of p-chloranil as a starting compound with n-propanethiol, n-pentanethiol, n-decanethiol, n-dodecanethiol, 2-methyl-2-propanethiol, and mixture of n-decanethiol and n-cyclohexanethiol as S-nucleophiles, were characterized by spectroscopic methods.

• 대한화학회지
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• 제13권4호
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• pp.297-302
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• 1969

The activation parameters for the nucleophilic addition reactions of n-propyl-, n-butyl-, n-amyl-and n-hexyl-mercaptan to 3, 4-methylene-dioxy-${\beta}$-nitrostyrene were determined at pH 5.8 and pH 2.0, and also the isokinetic temperature of the reactions at pH 5.8 was obtained numerically 262${\circ}$K, and at pH 2.0, 17.1${\circ}$K. From the values obtained above, the fact that the mercaptan having the longer carbon chain has the greater nucleophilicity of it in the addition reactions has been discussed by the extrathermodynamic analysis of ${\Delta}H^{\neq}$and ${\Delta}S^{\neq}$.

• 대한화학회지
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• 제9권3호
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• pp.148-151
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• 1965

Benzyl chloride 및 bromide와 chloride 및 bromide ion 간의 반응을 90% ethanol 용액에서반응속도론적으로 연구하였다. 반 정량적인 결과의 해석은 bond-formation 이 bond-breaking보다 더 중요하고 또 결합형성 과정에서는 형성으로 얻은 energy보다는 nucleophile의 electron affinity의 증가로 인한 차이가 더 중요함을 보여주고 있다.

• Bulletin of the Korean Chemical Society
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• 제25권8호
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• pp.1231-1237
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• 2004

Rate constants for photolytic reactions of p-substituted 2-diazopropiophenones were determined in acetonitrile. The reactions show a comparatively low value of activation energy and activation enthalpy to alkylcarbenes or other arylcarbenes. The transition state corresponds to the step of a new carbonyl bond formation. The high negative ρ -values are shown in Hammett plots. The kinetics results and EPR spectrum are in accord with a phenomenon that occurs in interconversion between singlet and triplet carbenes.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.137-140
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• 2011

The aminolysis reactions of phenyl N-benzyl thiocarbamate with benzylamines in acetonitrile at $50.0^{\circ}C$ are investigated. The reactions are first order in both the amine and the substrate. Under amine excess, pseudo-first coefficient ($k_{obs}$) are obtained, plot of $k_{obs}$ vs free amine concentration are linear. The signs of ${\rho}_{XZ}$ (< 0) are consistent with concerted mechanism. Moreover, the variations of $\rho_X$ and $\rho_Z$ with respect to the sustituent in the substrate and large ${\rho}_{XZ}$ value indicate that the reactions proceed concerted mechanism. The normal kinetic isotope effects ($k_H/k_D$ = 1.3 ~ 1.5) involving deuterated benzylamine nucleophiles suggest a hydrogen-bonded, four-centered-type transition state. The activation parameters, ${\Delta}H^\ddagger$ and ${\Delta}S^\ddagger$, are consistent with this transition state structure.