• Journal of the Korean Chemical Society
• /
• v.43 no.4
• /
• pp.456-460
• /
• 1999

Rates of 1-adamantyl fluoroformate with substituted pyridines ($3-CH_3,\;4-CH_3,\;H,\;3-Cl,\;3,4-(CH_3)_2,\;3,5-(CH_3)_2$) in methanol have been measured by conductometric method at various temperatures and concentrations. The activation parameters (${\Delta}H^{\neq},\;{\Delta}S^{\neq}$) and Hammett reaction constant (${\rho}$) or Bronsted coefficient (${\beta}$) were evaluated from rate constants. The activation entropies are large and negative, and the activation enthalpies are small and positive. The Hammett reaction constant (${\rho}$) and Bronsted coefficient (${\beta}$) values were -4.15 and 0.63, respectively. From the above results, it may be concluded that this reaction proceeds to a concerted displacement mechanism in methanol.

• Bulletin of the Korean Chemical Society
• /
• v.7 no.6
• /
• pp.413-421
• /
• 1986

Hydrocarbon solution of $Cp_2Zr(CH_3)Cl$ react rapidly with $Na_2Fe(CO)_4$ (1/2 equiv.) to yield $[Cp_2Zr(CH_3)]_2Fe(CO)_4$ and NaCl. The more soluble metal-metal bonded complex $[Cp_2ZrC_8H_{17}]_2Fe(CO)_2$ has also been prepared through the reaction of $Cp_2Zr(C_8H_{17})BF_4$ and $Na_2Fe(CO)_4 (1/2 equiv.). The complexes were characterized by IR, $^1H$ NMR, ^{13}C$ NMR, and elemental analysis. The infrared spectrum of $[Cp_2ZrR]_2Fe(CO)_4$ shows four bands, which is indicative of a cis-structure. The $^{13}C$ NMR spectrum provides evidence for the cis-structure.

• Tribology and Lubricants
• /
• v.4 no.2
• /
• pp.36-43
• /
• 1988

Titanium carbide(TiC) and titanium nitride(TiN) flims were deposited on $Si_3N_4$-TiC composite cutting tools by chemical vapor deposition(CVD) using $TiCl_4-CH_4-H_2$ and $TiCl_4-H_2-N_2$ gas mixtures, respectively. The nonmetal to metal ratio of deposit increases with increasing $m_{C/Ti}$(mole ratio of CH$_4$ to TiCl$_4$ in the input) for TiC coatings and $m_{N/Ti}$(mole ratio of N$_2$ to TiCl$_4$ in the input) for TiN coatings. The nearly stoiahiometric films could be obtained under the deposition condition of $m_{C/Ti}$ between 1.15 and 1.61 for TiC, and that of $m_{N/Ti}$ between 25 and 28 for TiN. Also maximum microhardness of the coatings can be obtained in these ranges. The interfacial region of TiC coatings on $Si_3N_4$-TiC ceramics is wider than that of TiN coatings according to Auger depth profile analysis, which indicates good interfacial bonding for TiC. Experimental results show that TiC coatings have an randomly equiaxed structure and Columnar structure with(220) preferred orientation can be obtained for TiN coatings. And, multilayer coatings have a dense and equiaxed structure.

• Proceedings of the Korean Fiber Society Conference
• /
• 1991.06b
• /
• pp.87-87
• /
• 1991

• Bulletin of the Korean Chemical Society
• /
• v.14 no.2
• /
• pp.195-200
• /
• 1993

The neutral, reduced, and oxidized 2,2-trans isomers of $Rh_2(ap)_4$ (ap=2-anilinopyridinate) were investigated with respect to dioxygen binding in $CH_2Cl_2$ containing 0.1 M tetrabutyl-ammonium perchlorate. $Rh_2(ap)_4$ binds dioxygen in nonaqueous media and forms a $Rh^{II}Rh^{III}$ superoxide complex, $Rh_2(ap)_4(O_2)$. This neutral species was isolated and is characterized by UV-visible and IR spectroscopy, mass spectrometry and cyclic voltammetry. It can be reduced by one electron at $E_{1/2}$ = -0.45 V vs. SCE in $CH_2Cl_2$ and gives ${[Rh_2(ap)_4(O_2)]}^-$ as demonstrated by the ESR spectrum of a frozen solution taken after controlled potential reduction. The superoxide ion in ${[Rh_2(ap)_4(O_2)]}^-$ is axially bound to one of the two rhodium ions, both of which are in a +2 oxidation state. $Rh_2(ap)_4(O_2)$ can also be stepwise oxidized in two one-electron transfer steps at $E_{1/2}$ = 0.21 V and 0.85 V vs. SCE in $CH_2Cl_2$ and gives ${[Rh_2(ap)_4(O_2)]}^+$ followed by ${[Rh_2(ap)_4(O_2)]}^{2+}$. ESR spectra demonstrate that the singly oxidized complex is best described as ${[Rh^{II}Rh^{III}(ap)_4(O_2)]}^+$ where the odd electron is delocalized on both of the two rhodium ions and the axial ligand is molecular oxygen.

• Korean Journal of Pharmacognosy
• /
• v.39 no.4
• /
• pp.347-351
• /
• 2008

The methanol (MeOH) extract of the rhizome of Alpinia officinarum Hance (Zingiberaceae) demonstrated a potent inhibition on the proliferation of cultured human tumor cell lines such as MES-SA (human uterine carcinoma cell line), MESSA/DX5 (multidrug resistant subline of MES-SA), HCT-15 (human colorectal adenocarcinoma cell line), HCT15/CL02 (multidrug resistant subline of HCT15). The MeOH extract was fractionated into four portions by serial solvent partition, ie., methylene chloride (CH2Cl2) soluble part, ethylacetate (EtOAc) soluble part, n-butanol (BuOH) soluble part and remaining water layer. Among them, the $CH_2Cl_2$ soluble part of the extract exhibited a most potent inhibition on the proliferation of tested tumor cell lines. Bioassay-guided fractionation of the $CH_2Cl_2$ soluble part led to the isolation of five diarylheptanoid and two flavonoid constituents, i. e., galangin (1), 7-(4"-hydroxy-3"-methoxyphenyl)-1-phenylhept-4-en-3-one (2), 1,7-diphenyl-5-hydroxy-3-heptanone (3), trans,trans-1-(3'-methoxy-4'-hydroxyphenyl)-7-phenyl-5-ol-4,6-dien-3-heptanone (4), 5-methoxy-7-(4"-hydroxy-3"-methoxyphenyl)-1-phenyl-3-heptanone (5), kaempferide (6), 5-hydroxy-7-(4"-hydroxy-3"-methoxyphenyl)-1-phenyl-3-heptanone (7). Structures of the isolated active components (1 - 7) were established by chemical and spectroscopic means.

• Journal of the Korean Wood Science and Technology
• /
• v.40 no.2
• /
• pp.141-146
• /
• 2012

The outer bark of Prunus sargentii was collected, air-dried and extracted with 70% aqueous acetone. Then it was successively partitioned with n-hexane, dichloromethane ($CH_2Cl_2$), ethyl acetate (EtOAc) and $H_2O$. From the EtOAc soluble fraction, four compounds were isolated by the repeated Sephadex LH-20 column chromatography. The isolated compounds were determined as (+)-catechin (1), (-)-epicatechin (2), taxifolin (3), and neosakuranin (4) by the spectroscopic analysis including $^1H$, $^{13}C$-NMR, and 2D-NMR spectrometers. The antioxidative activities on the isolated compounds and the separated fractions were evaluated by DPPH radical scavenging assay. The crude, EtOAc, and $H_2O$ soluble fractions indicated good antioxidative potential compared to the $CH_2Cl_2$ and n-hexane soluble fractions.

• Electronic Materials Letters
• /
• v.14 no.6
• /
• pp.700-711
• /
• 2018

CdS synthesized by the chemical bath method at $70^{\circ}C$, has been used as an electron transport layer in the planar structure of the perovskite solar cells. A two-step spin process produced a mixed halide perovskite of $CH_3NH_3PbI_{3-x}Cl_x$ and a mixture of $PbCl_2$ and $PbI_2$ was deposited on CdS, followed by a sub-sequential reaction with MAI ($CH_3NH_3I$). The added $PbCl_2$ to $PbI_2$ in the first spin-step affected the structure, orientation, and shape of lead halides, which varied depending on the content of Cl. A small amount of Cl enhanced the surface morphology and the preferred orientation of $PbI_2$, which led to large and uniform grains of perovskite thin films. In contrast, the high content of Cl produces a new phase PbICl in addition to $PbI_2$, which leads to the small and highly uniform grains of perovskites. An improved surface coverage of perovskite films with the large and uniform grains maximized the performance of perovskite solar cells at 0.1 molar ratio of $PbCl_2$ to $PbI_2$. The depth profiling of elements in both lead halide films and mixed halide perovskite films were measured by Rutherford backscattering spectroscopy, revealing the distribution of chlorine along with the thickness, and providing the basis for the mechanism for enhanced preferred orientation of lead halide and the microstructure of perovskites.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.12
• /
• pp.974-978
• /
• 2012

The effect of Cu coating on the sensing properties of nano $SnO_2:Cu$ based sensors for the $CH_4$, $CH_3CH_2CH_3$ gas was studied. This work was focussed on investigating the change of sensitivity of nano $SnO_2:Cu$ based sensors for $CH_4$, $CH_3CH_2CH_3$ gas by Cu coating. Nano sized $SnO_2$ powders were prepared by solution reduction method using stannous chloride($SnCl_2{\cdot}2H_2O$), hydrazine($N_2H_2$) and NaOH and subsequent heat treatment. XRD patterns showed that nano $SnO_2$ powders with rutile structure were grown with (110), (101), (211) dominant peak. The particle size of nano $SnO_2:Cu$ powders at 8 wt% Cu was about 50 nm. $SnO_2$ particles were found to contain many pores, according to SEM analysis. The sensitivity of nano $SnO_2:Cu$ based sensors was measured for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in target gases. The sensitivity for both $CH_4$ and $CH_3CH_2CH_3$ gases was improved by Cu coating on the nano $SnO_2$ surface. The response time and recovery time of the $SnO_2:Cu$ gas sensors for the $CH_4$ and $CH_3CH_2CH_3$ gases were 18~20 seconds, and 13~15 seconds, respectively.

• Archives of Pharmacal Research
• /
• v.29 no.3
• /
• pp.191-194
• /
• 2006

Twigs from llex macropoda were extracted with MeOH, and the concentrated extracts were partitioned with $CH_2Cl_2$, EtOAc, n-BuOH, and $H_2O$. Repeated column chromatography of the $CH_2Cl_2$ fraction ultimately resulted in the isolation of two compounds, via activity-guided fractionation, using ACAT inhibitory activity measurements. According to the physico-chemical data, the chemical structures of these isolated compounds were identified as lupeol (1) and betulin (2). Compounds 1 and 2 were shown to inhibit the activity of hACAT-1 and hACAT-2 in a dose-dependent manner, and compounds 1 and 2 inhibited hACAT-1 with $IC_{50}$ values of 48 and $83{\mu}M$, respectively.