• 대한화학회지
• /
• 제36권2호
• /
• pp.174-179
• /
• 1992

$CHCl_3,\;CHCl_3 : CH_2Cl_2$(1 : 1), 및 $CH_2Cl_2$ 용매 중에서 aniline과 iodine간의 반응을 전도도법을 이용하여 속도론적으로 조사하였다. 유사 1차반응 속도상수($k_{obs}$) 및 2차 반응속도상수 ($k_{obs}$/[aniline])가 aniline 농도 의존성을 보였다. 실험적으로 구한 2차반응 속도 상수는 aniline 농도 증가와 더불어 증가하였다. 이러한 결과를 반응중간체로서 전하이동 착물생성에 기인하는 것으로 보고, 반응 메카니즘의 설정과 속도식의 유도로부터 착물 생성에 따른 평형상수와 변환에 따른 활성화 파라미터를 계산하였다. 평형상수는 용매의 유전상수의 증가와 더불어 감소하였으며, 1.7-3.7$M^{-1}$의 값을 보였다. 또한 변환의 빠르기는 용매의 극성에 크게 의존하였으며, ${\Delta}H^{\neq}$ 값은 약 14.2kJ/mol, ${\Delta}S^{\neq}$값은 약 -243j/mol K의 큰 음의 값을 나타내었다.

• Bulletin of the Korean Chemical Society
• /
• 제35권6호
• /
• pp.1633-1638
• /
• 2014

[6]-Gingerol is known as the major bioactive constituent of ginger. In the study, it was observed to effectively protect against ${\bullet}OH$-induced DNA damage ($IC_{50}$ $328.60{\pm}24.41{\mu}M$). Antioxidant assays indicated that [6]-gingerol could efficiently scavenge various free radicals, including ${\bullet}OH$ radical ($IC_{50}$ $70.39{\pm}1.23{\mu}M$), ${\bullet}O_2{^-}$ radical ($IC_{50}$ $228.40{\pm}9.20{\mu}M$), $DPPH{\bullet}$radical ($IC_{50}$ $27.35{\pm}1.44{\mu}M$), and $ABTS{^+}{\bullet}$radical ($IC_{50}$ $2.53{\pm}0.070{\mu}M$), and reduce $Cu^{2+}$ ion ($IC_{50}$ $11.97{\pm}0.68{\mu}M$). In order to investigate the possible mechanism, the reaction product of [6]-gingerol and $DPPH{\bullet}$ radical was further measured using HPLC combined mass spectrometry. The product showed a molecular ion peak at m/z 316 $[M+Na]^+$, and diagnostic fragment loss (m/z 28) for quinone. On this basis, it can be concluded that: (i) [6]-gingerol can effectively protect against ${\bullet}OH$-induced DNA damage; (ii) a possible mechanism for [6]-gingerol to protect against oxidative damage is ${\bullet}OH$ radical scavenging; (iii) [6]-gingerol scavenges ${\bullet}OH$ radical through hydrogen atom ($H{\bullet}$) transfer (HAT) and sequential electron (e) proton transfer (SEPT) mechanisms; and (iv) both mechanisms make [6]-gingerol be oxidized to semi-quinone or quinone forms.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.401-401
• /
• 2016

Although vertically aligned one-dimensional (1D) structure has been considered as efficient forms for photoelectrode, development of efficient 1D nanostructured photocathode are still required. In this sense, we recently demonstrated a simple fabrication route for CuInS2 (CIS) nanorod arrays from aqueous solution by template-assisted growth-and-transfer method and their feasibility as a photoelectrode for water splitting. In this study, we further evaluated the photoelectrochemical properties surface-modified CIS nanorod arrays. Surface modification with CdS and ZnS was performed by successive ion layer adsorption and reaction (SILAR) method, which is well known as suitable technique for conformal coating throughout nanoporous structure. With surface modification of CdS and ZnS, both photoelectrochemical performance and stability of CuInS2 nanorod arrays were improved by shifting of the flat-band potential, which was analyzed both onset potential and Mott-schottky plot.

• Bulletin of the Korean Chemical Society
• /
• 제13권3호
• /
• pp.274-279
• /
• 1992

Immobilization method of lariat azacrown ethers, containing hydroxyl group in the side arm of crown ring, on the polymer matrix and the phase-transfer catalytic activity of thus obtained immobilized lariat azacrown ethers were studied. Polystyrene resins with crown ether structures and hydroxyl groups adjacent to the macrorings were prepared by the reaction of crosslinked polystyrene resins containing epoxy groups with monoaza-15-crown-5 or monoaza-18-crown-6. Microporous crosslinked polystyrene resins containing epoxy group for the syntheses of these immobilized lariat crown catalysts were prepared by suspension polymerization of styrene, divinylbenzene (DVB 2%) and vinylbenzylglycidyl ether. The immobilized lariat catalysts with 10-20% ring substitution exhibited maximal activity for the halogen exchange reactions of 1-bromooctane with aqueous KI or NaI under triphase heterogeneous conditions. Immobilized catalyst exhibited higher activity than corresponding catalyst without the hydroxyl group and this result was suggested that the active site have a structure in which the $K^+$ ion was bound by the cooperative coordination of the crown ring donors and the hydroxyl group in the side arm.

• Mass Spectrometry Letters
• /
• 제12권4호
• /
• pp.146-151
• /
• 2021

In this study, the hydrogen/deuterium (HDX) exchange mechanism of active hydrogen, nitrogen, and sulfur-containing polycyclic aromatic hydrocarbon (PAH) dissolved in toluene and deuterated methanol by atmospheric pressure photoionization (APPI) is investigated. The comparison of the data obtained using APPI suggests that aniline and benzene-1,2-dithiol contain two exchanging hydrogens. The APPI HDX that best explains the experimental findings was investigated with the use of quantum mechanical calculations. The HDX mechanism is composed of a two-step reaction: in the first step, analyte radical ion gets deuterated, and in the second step, the hydrogen transfer occurs from deuterated analyte to de-deuterated methanol to complete the exchange reaction. The suggested mechanism provides fundamentals for the HDX technique that is important for structural identification with mass spectrometry. This paper is dedicated to Professor Seung Koo Shin for his outstanding contributions in chemistry and mass spectrometry.

• 공업화학
• /
• 제28권5호
• /
• pp.597-600
• /
• 2017

4,4'-비피리딘과 크롬(VI) 산화물을 반응시켜 $(C_{10}H_8N_2H)_2Cr_2O_7$을 합성하였다. 적외선분광광도법(FT-IR)과 원소분석으로 구조를 확인하였다. 여러 가지 용매 하에서 $(C_{10}H_8N_2H)_2Cr_2O_7$을 이용하여 벤질알코올의 산화반응을 측정한 결과, 용매의 유전상수 값이 증가함에 따라 반응수율이 증가했다. 그 순서는 DMF (N,N'-디메틸포름아미드) > 아세톤 > 클로로포름 > 시클로헥센이었다. $H_2SO_4$ 촉매를 이용한 DMF 용매 하에서, $(C_{10}-H_8N_2H)_2Cr_2O_7$은 벤질알코올(H)과 그의 유도체들($p-OCH_3$, $m-CH_3$, $m-OCH_3$, m-Cl, $m-NO_2$)을 효과적으로 산화시켰다. 전자받개 그룹들은 반응속도가 감소한 반면에 전자주개 치환체들은 반응속도를 증가시켰고, Hammett 반응상수(${\rho}$) 값은 -0.70 (308 K)이었다. 본 실험에서 알코올의 산화반응 과정은 속도결정단계에서 수소화 전이가 일어났다.

• Macromolecular Research
• /
• 제16권2호
• /
• pp.108-112
• /
• 2008

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of nonpolar polymeric materials is affected by the sample preparation as well as the matrix and cationizing agent. This study examined the influence of silver salt types on the MALDI analysis of polybutadiene (PB). Silver trifluoroacetate (AgTFA), silver benzoate (AgBz), silver nitrate ($AgNO_3$), and silver p-toluenesulfonate (AgTS) were used as the silver salts to compare the MALDI mass spectra of PB. The mixture solution of PB and 2,5-dihydroxybenzoic acid (DHB), as a matrix dissolved in THF, was spotted on the sample plate and dried. A droplet of the aqueous silver salt solution was placed onto the mixture. The mass spectrum with AgBz showed the clear $[M+Ag]^+$ ion distribution of PB while the mass spectrum with AgTFA did not show $[M+Ag]^+$ ions but only silver cluster ions. The mass spectra with $AgNO_3$ and AgTS did not show a clear $[M+Ag]^+$ ion distribution. The difference in the formation of $[M+Ag]^+$ ions of PB depending on the silver salts was attributed to the silver cation transfer reaction between the silver salt and the matrix (DHB). The mass spectrum showed a clear $[M+Ag]^+$ ion distribution of PB when the conjugate acid of the silver salt was less acidic than the matrix.

• 분석과학
• /
• 제20권5호
• /
• pp.406-412
• /
• 2007

분광 광도법을 이용하여 ${\beta}$-CD와 $[Cu(dien)(sub-py)]^{2+}$ 이온 간의 복합체 형성에 관한 연구를 하였다. ${\beta}$-CD와 $Cu^{2+}$ 착물이 복합체를 형성 할 때 ${\gamma}_{max}$은 리간드에 전자 주는기($CH_3$)가 치환 된 경우는 $^2T_2{\rightarrow}^2E$로 한 곳에서, 전자 끄는기(Cl)가 치환된 경우는 $^2T_2{\rightarrow}^2E$와 MLCT에 의하여 두 곳에서 나타났다. 형성상수는 온도가 올라가면 결합에너지의 감소로 작아졌다. 모든 반응은 엔트로피의 감소를 보였으나 큰 발열반응으로 자발적 반응이었다. 치환기 상수(${\sigma}_x$)에 따른 Hammett plot 결과 좋은 직선성(${\gamma}=0.996$)을 보여 형성상수를 정량적으로 설명할 수 있었다.

• 분석과학
• /
• 제9권3호
• /
• pp.292-301
• /
• 1996

산화환원반응 탐침제로, poly ether 꼬리가 결합된 Cobalt(II)bipyridine 착물을 합성 하였고, 이들 화합물의 느린 확산계수와 불균일 전자이동을 설명하였다. $Co(bpy(ppgm)_2)_{3^-}(ClO_4)_2$에 전해질 $LiClO_4$가 혼합된 neat 상태의 산화반응에 대한 확산계수는 $1.5{\times}10^{-15}cm^2/s$ 였다. 이 화합물들의 불균일 전자이동 속도상수들은 확산계수와 관련이 있었다. 확산계수의 감소에 따라 속도상수(k)의 감소가 일어났다. 강한 이온쌍을 형성하는 $ClO{_4}^-$의 화합물은 약한 이온 쌍을 형성하는 $CF_3COO^-$ 화합물보다 확산계수가 훨씬 작았다.

• Journal of Electrochemical Science and Technology
• /
• 제12권2호
• /
• pp.279-284
• /
• 2021

The high theoretical specific capacity of lithium-sulfur (Li-S) batteries makes them a more promising energy storage system than conventional lithium-ion batteries (LIBs). However, the slow kinetics of the electrochemical conversion reaction seriously hinders the utilization of Li-S as an active battery material and has prevented the successful application of Li-S cells. Therefore, exploration of alternatives that can overcome the sluggish electrochemical reaction is necessary to increase the performance of Li-S batteries. In this work, an ionic liquid (IL) is proposed as a functional additive to promote the electrochemical reactivity of the Li-S cell. The sluggish electrochemical reaction is mainly caused by precipitation of low-order polysulfide (l-PS) onto the positive electrode, so the IL is adopted as a solubilizer to remove the precipitated l-PS from the positive electrode to promote additional electron transfer reactions. The ILs effectively dissolve l-PS and greatly improve the electrochemical performance by allowing greater utilization of l-PS, which results in a higher initial specific capacity, together with a moderate retention rate. The results presented here confirmed that the use of an IL as an additive is quite effective at enhancing the overall performance of the Li-S cell and this understanding will enable the construction of highly efficient Li-S batteries.