• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.126-126
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• 2017

Using first principles calculations we unveil fundamental mechanism of hydrolysis reactions of two hazardous chemicals $PCl_3$ and $POCl_3$ with molecular water clusters nearby. It is found that the water molecules play a key role as a catalyst significantly lowing the activation barriers by transferring its protons to the reaction intermediates. Interestingly, torsional angles of molecular complexes at transition states are identified as a vital descriptor on the reaction rate. Analysis of charge distribution over the complexes further reinforces the finding with atomic level correlation between the torsional angle and variation of the orbital hybridization state of P in the complex. Electronic charge separation (or polarization) enhances thermodynamic stability of the activated complex at transition state and reduces the activation energy through hydrogen bonding network with water molecules nearby. Calculated potential energy surfaces (PES) for the hydrolysis reactions of $PCl_3$ and $POCl_3$ depict their two contrastingly different profiles of double- and triple-deep wells, respectively. It is ascribed to the unique double-bonding O=P in the $POCl_3$. Our results on the activation free energy show well agreements with previous experimental data within $7kcalmol^{-1}$ deviation.

• 한국세라믹학회지
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• 제34권8호
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• pp.811-816
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• 1997

SiO2-P2O5-B2O3 glass soot was fabricated by flame hydrolysis deposition and their properties by SEM, XRD, TGA-DSC were investigated., The mechanism of consolidation process of a glass soot as a function of consolidation temperature was analyzed by SEM observations. In the XRD patterns, the crystalline peaks which seem to be generated from B2O3 and BPO4 were observed. When the temperature of heat treatment exceeded 105$0^{\circ}C$, the non-crystalline state of SiO2-P2O5-B2O3 glass was observed. In the TGA-DSC curves, the evaporation of water molecule by a sudden endothermic reaction was observed at 128$^{\circ}C$ and a broad endothermic peak was seen in the temperature range of 40$0^{\circ}C$-95$0^{\circ}C$, without any weight loss. Finally, this peak was began to recover its baseline at 953$^{\circ}C$. This point is equal to the temperature at which the densification begins. Furthermore, we observed that the addition of dopants such as P2O5 and B2O3 decrease the onset of consolidation temperature till 95$0^{\circ}C$.

• 대한화학회지
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• 제17권2호
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• pp.130-135
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• 1973

여러 pH에서 3,4-methylenedioxyphenylmethyllenemalonitrile의 가수분해속도상수를 자외선분광광도법에 의하여 측정하여 넓은 궤도 범위에서 잘 맞는 반응속도식을 구하였다. 이 속도식에 의하면 가수분해 반응메카니즘 특히 종전에 잘 규명된 바 없는 산성 용매 속에서의 반응 과정을 잘 설명할 수 있다. 즉 pH 5 이하에서는 물의 첨가로서 가수분해가 시작되며 pH 6∼8 사이에서는 물분자와 수산화이온의 첨가가 경쟁적으로 일어나나 pH 9 이상에서는 수산화이온만이 첨가된다. 한편 친핵성 시약과 촉매 역할을 겸하고 있는 수산화이온 및 물의 역할로 잘 설명할 수가 있었다.

• 대한화학회지
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• 제31권4호
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• pp.352-358
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• 1987

$25^{\circ}C$의 1 : 4 dioxane-물의 혼합용액속에서 파라-치환된 phenyl N-(p-chlorobenzoyl)chloroformimidate (I) 유도체들의 가수분해 반응속도 상수를 측정하고 반응속도식, 치환기 효과$(\rho\>{\rho}^+)$, 생성물 분석 및 분자궤도 함수의 계산 결과로부터 pH3.0 이하에서는 azocarbonium 이온(II)이 생성되는 $S_N1$반응 메카니즘으로 무촉매 반응이 일어나며, pH 4.0이상에서는 전이상태(III)를 지나는 $S_N2$반응 메카니즘을 통하여 염기 촉매반응이 일어남을 제안 할 수 있었다. 4가지 peri planar형태 이성질체들의 상대적인 안정도는 각각 (E-ap) > (Z-ap) > (E-sp) > 및 (Z-ap)이었고, (E-ap)형태의 가장 안정한 입체구조는 benzimidochloroformyl group면에 대하여 Y-치환 phenyl group이 수직$(90^{\circ})$을 이루었으며 (I)의 활성화된 azomethine탄소 원자에 대하여 물분자는 시그마 공격에 의하여 친핵성 반응이 일어난다.

• 공업화학
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• 제7권4호
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• pp.794-801
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• 1996

Isopropanol 용매 내에서 titanium isopropoxide($Ti(O-^iPr)_4$)의 가수분해반응에 의하여 $TiO_2$ 미분말을 합성하였고 가수분해 반응 속도를 자외선분광법에 의하여 측정하였다. 반응은 $Ti(O-^iPr)_4$의 농도에 비하여 물 농도를 크게 하여 유사일차반응으로 진행시켰고, 물 농도 및 온도의 변화에 따른 반응속도상수를 Guggenheim method로 계산하였다. 또한 물의 동위원소 효과를 측정하여 반응에 참여하는 물분자의 촉매성을 확인하였다. 입도분석과 미세구조 관찰 결과, 얻어진 $TiO_2$ 미분말은 $0.3{\mu}m$정도의 입자크기를 갖는 구형의 입자로 확인되었다. 또한 반응속도로부터 전이상태에 참여하는 n value와 열역학적 파라메타를 계산한 결과, $Ti(O-^iPr)_4$의 가수분해반응은 이분자 반응인 $S_N2$ mechanism으로 진행하는 것으로 추정되었다.

• Journal of Pharmaceutical Investigation
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• 제33권2호
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• pp.91-97
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• 2003

During the preparation of decoction from the mixture of Coptidis Rhizoma and Scutellariae Radix, insoluble copreciptate was formed. The coprecipitated product (COP) was composed of berberine and baicalin which was the active ingredient of Coptidis Rhizoma and Scutellariae Radix, respectively. COP was slightly soluble in water and could not be well absorbed after oral administration. This poor bioavailibility might be associated with its poor aqueous solubility. With the purpose of increasing the solubility and bioavailibility of COP, hydrolysis of COP by ${\beta}-glucuronidase$ was carried out. Hydrolyzed products (HOP) of COP were identified and assayed for active ingredients. The partition coefficient study, in situ absorption test, and pharmacokinetic study after oral administration were also performed. COP was found to be consisted of berberine and baicalin with molecular ratio of 1 to 1. This compound was hydrolyzed to berberine and baicalin by ${\beta}-glucuronidase$. The rate of hydrolysis was higher at higher temperature up to $50^{\circ}C$ and higher concentration of ${\beta}-glucuronidase$ up to 2500 unit under our experimental conditions. Baicalein, which is more liphophilic than baicalin, showed greater absorption in small intestine than baicalin did. The plasma concentrations of berberine and baicalein after oral administration of HOP were significantly higer than those of COP. The possible mechanism of increased bioavailibility of berberine and baicalein could be the hydrolysis of COP by ${\beta}-glucuronidase$. On the basis of the above results, it might be said that HOP should be a suitable preparation for increasing the bioavailibility of Coptidis Rhizoma and Scutellariae Radix.

• 대한화학회지
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• 제28권4호
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• pp.259-264
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• 1984

1 : 4 dioxane-물의 혼합용매중에서 benzenesulfonylimido phosgene의 가수분해 반응속도 상수를 자외선 분광법으로 측정하여 넓은 pH범위에서 잘 맞는 반응속도식을 구하였다. Grunwald-Winstein식에 적용하여 pH4.0에서 m=0.4의 값을 얻었으며 열역학적 활성화 파라미터 값은 pH4.0에서 ${\Delta}H^{\neq}$ = 15kcal/mol과 $ {\Delta}S^{\neq}$ =-21e.u 그리고 pH10.0에서는 $ {\Delta}H^{\neq}$ = 8kcal/mol, ${\Delta}S^{\neq}$ = -39e.u.이었다. 이와 같은 결과로부터 잘 알려져 있지않은 benzenesulfonylimido phosgene의 친핵성 첨가-제거 반응메카니즘을 정량적으로 잘 설명할 수 있었다.

• 대한화학회지
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• 제28권5호
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• pp.328-334
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• 1984

새로운 4가지의 phenyl N-benzenesulfonylchloroformimidate 유도체를 합성하고 $25^{\circ}C$와 1 ; 4 dioxane-물의 이성분 혼합용매중에서 가수분해 반응속도를 자외선 분광 광도법으로 측정하여 넓은 pH범위에 적용되는 가수분해 반응속도식을 유도하였다. 치환기 효과(${\rho}$ = -0.45, ${\rho}$ = 0.40), 용매효과 (m = 1.3-1.5, n = 5.0-5.5), 반응속도식 및 생성물 분석 등의 결과로부터 가수분해 반응 메카니즘을 제안하였다. 즉, pH 0.0-8.0의 산성과 중성용액에서는 $SN_1$, 그리고 pH 10.0이상의 알카리성 용액에서는 $SN_2$반응으로 가수분해가 시작되어 $E_1CB$반응으로 benzensulfonamide를 생성하는 일련의 반응으로 가수분해가 진행됨을 알았다.

• Applied Biological Chemistry
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• 제39권1호
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• pp.70-76
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• 1996

일련의 pyridylsulfonyl urea들을 합성하고 25%(v/v) 디옥산 수용액의 넓은 pH범위에서 가수분해 반응속도 상수를 측정하였다. pH-효과, 용매 효과($m{\ll}1,\;n{\ll}3$ 및 ${\mid}m{\mid}{\ll}{\mid}{\ell}{\mid}$), 일반 염기-효과, 산-해리상수(pKa, 3: 4.9 및 5: lit.4.6), 열역학적 활성화 파라미터(${\Delta}H^{\neq}=0.025\;Kcal.mol.^{-1}$ 및 ${\Delta}S^{\neq}=0.54{\sim}\;-2.19\;e.u.$) 및 생성물 분석 결과로부터 반응속도식을 유도하고 가수분해 반응 메카니즘을 제안하였다. 즉, 비(H)치환체, 1-(4,6-dimethoxypyrimidine-2-yl)-3-(2-pyridylsulfonyl) urea, 3은 산성용액에서 A-2형(또는 $A_{AC}2$)반응 그리고 염기성 용액 에서는 $(E_1)_{anion}$ 메카니즘으로 가수분해 반응이 일어난다. 반면에 trifluoromethyl-치환체, 1-(4,6-dimethoxypyrimidine-2-yl)-3-(3-trifluorornethyl-2-pyridylsulfonyl) urea, 5(Flazasulfuron)는 산성 용액중에서 $A-S_N2Ar$형의 반응으로 생성된 conjugate acid($5H^+$), 그리고 pH 9.0 이상에서는 $(E_1)_{anion}$ 및 $(E_1CB)_R$ 반응으로 생성된 conjugate base(CB)를 거쳐 산성 및 염기성 용액중에서 모두 5원자 고리 중간체를 경유하는 Smile 자리옮김 반응으로 산성에서는 3-trifluoromethyl-2-pyridylpyrimidinyl urea(PPU) 그리고 염기성에서는 3-trifluoromethyl-2-pyridyl-4,6-dimethoxy-pyrimidinyl amine(PPA)을 생성하는 가수분해 반응이 일어남을 알았으며 5는 3보다 약 3.5배 빠른 반응속도를 나타내었다.

• Archives of Pharmacal Research
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• 제25권6호
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• pp.873-878
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• 2002

OA-8159, a new Phosphodiesterase (PDE) 5 inhibitor, has exhibited potent erectogenic potential in a penile erection test in rats and anesthetized dogs. In this study, we investigated the mechanism of its erectogenic activity by measuring the activity of OA-8159 against a various PDE isozymes and assessing cGMP and cAMP formation in a rabbit corpus cavernosum in vitro. DA-8159 inhibited the PDE 5 activity in rabbit and human platelets, which the $IC_{50}$ was 5.84$\pm$1.70 nM and 8.25$\pm$2.90 nM, respectively. The $IC_{50}$ of DA-8159 on PDE 1, PDE2, PDE 3 and PDE 6 were 870$\pm$57.4 nM, $101\pm$5 $\mu$M, 52.0$\pm$3.53 $\mu$M and 53.3$\pm$2.47 nM, respectively. This suggests that DA-8159 is a potent, highly selective, competitive inhibitor of PDE 5-catalyzed cGMP hydrolysis. The rates of cGMP hydrolysis catalyzed by human platelets-derived PDE 5 as a function of the cGMP concentration (5~100 nM) and two-fixed DA-8159 concentration (11.3 and 18.8 nM) were investigated in order to characterize the mode of PDE 5 inhibition by DA-8159. DA-8159 increased the apparent 4K_{m}$ value for cGMP hydrolysis but had no effect on the apparent $V_{max}$, indicating a competitive mode of inhibition. DA-8159 increased the cGMP concentrations in the rabbit corpus cavernosum dose dependently. In the presence of sodium nitroprusside (SNP), DA-8159 significantly sti\mulated the accu\mulation of cGMP when compared to the control level. This indicated that the enhancement of a penile erection by DA-8159 involved the relaxation of the cavernosal smooth \muscle by NO-sti\mulated cGMP accu\mulation. In conclusion, DA-8159 is a selective inhibitor of PDE 5-catalyzed cGMP hydrolysis and the enhancement of a penile erection by DA-8159 is mediated by the relaxation of the cavernosal smooth \muscle by the NO-sti\mulated cGMP accu\mulation.