• Bulletin of the Korean Chemical Society
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• 제8권3호
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• pp.185-189
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• 1987

Reactions of $Ir(ClO)_4(CO)(PPh_3)_2$ with dicyano olefins, cis-NCCH = CH$CH_2$$CH_2$CN (cDC1B), trans-NCCH = CH$CH_2$$CH_2$CN (tDC1B), trans-NC$CH_2$CH = CH$CH_2$CN (tDC2B), and NC$CH_2$$CH_2$$CH_2$$CH_2$CN (DCB) produce binuclear dicationic iridium (I) complexes, $[(CO)(PPh_3)_2Ir-NC-A-CN-Ir(PPh_3)_2(CO)](ClO_4)_2$ (NC-A-CN = cDC1B (1a), tDC1B (1b), tDC2B (1c), DCB (1d)). Complexes 1a-1d react with hydrogen to give binuclear dicationic tetrahydrido iridium (Ⅲ ) complexes, $[(CO)(PPh_3)_2(H)_2Ir-NC-A-CN-Ir(H)_2(PPh_3)_2(CO)](ClO_4)_2$ (NC-A-CN = cDC1B (2a), tDC1B (2b), tDC2B (2c), DCB (2d)). Complexes 2a and 2b catalyze the hydrogenation of cDC1B and tDC1B, respectively to give DCB, while the complex 2c is catalytically active for the isomerization of tDC2B to give cDC1B and tDC1B and the hydrogenation of tDC2B to give DCB at $100^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제11권2호
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• pp.109-114
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• 1990

The anionic transition metal hydrides $(HW(CO)_4P(OMe)_3\;^-,\;HW(CO)_5\;^-,\;HCr(CO)_5\;^-,\;HFe(CO)_4\;^-)$ react with transition metal alkyl $(CpMo(CO)_3(CH_3)$ to yield $CH_4\;and\;CH_3CHO$ in addition to the inorganic products $(CpMo(Co)_3\;^-$, etc.). The reaction of these anionic metal hydrides with CpMo(CO)3{CH2CH(CH2)2} may lead to an elucidation of the reaction mechanisms involved; the organic product distributions are among $CH_4,\;CH_2\;=\;CHCH_2CH_3$, and $CH_3CH(CH_2)_2$, depending upon the anionic metal hydride used. These anionic metal hydrides also are reported to undergo a hydride-halide exchange reaction with organic halides; therefore, these similar reactions have been compared in terms of leaving group ability $(CpMo(CO)_3\;^-\;vs.\;Br^-)$ and the mechanistic pathways.

• Bulletin of the Korean Chemical Society
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• 제7권6호
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• pp.466-468
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• 1986

Reaction of $Ir(ClO_4)(CO)(PPh_3)_2$ with trans-$C_6H_5CH$ = $CHCO_2C_2H_5$ produces a new cationic iridium(I) complex, [Ir (trans-$C_6H_5CH$ = $CHCO_2C_2H_5)(CO)(PPh_3)_2]ClO_4$ where trans-$C_6H_5CH$ = $CHCO_2C_2H_5$ seems to be coordinated through the carbonyl oxygen rather than through the $\pi$-system of the olefinic group according to the spectral data. It has been found that Ir$(ClO_4)(CO)(PPh_3)_2$ catalyzes the hydrogenation of $CH_2$ = $CHCO_2C_2H_5$, trans-$CH_3CH$ = $CHCO_2C_2H_5$ and trans-$C_6H_5CH$ = $CHCO_2C_2H_5$ to $CH_3CH_2CO_2C_2H_5$, $CH_3CH_2CH_2CO_2C_2H_5$ and $C_6H_5CH_2CH_2CO_2C_2H_5$, respectively at room temperature under the atmospheric pressure of hydrogen. The relative rates of the hydrogenation of the unsaturated esters are mostly understood in terms of steric reasons.

• Bulletin of the Korean Chemical Society
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• 제23권6호
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• pp.811-817
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• 2002

Gibbs ensemble Monte Carlo simulations were performed to calculate the vapor-liquid coexistence properties for the binary mixtures $CO_2/CH_3OH$, $CO_2/C_2H_5OH$, and $CO_2/CH_3CH_2CH_2OH.$ The configurational bias Monte Carlo method was used in the simulation of alcohol. Density of the mixture, composition of the mixture, the pressure-composition diagram, and the radial distribution function were calculated at vapor-liquid equilibrium. The composition and the density of both vapor and liquid from simulation agree considerably well with the experimental values over a wide range of pressures. The radial distribution functions in the liquid mixtures show that $CO_2$ molecules interact more stogly with methyl group than methylene group of $C_2H_5OH$ and $CH_3CH_2CH_2OH$ due to the steric effects of the alcohol molecules.

• Bulletin of the Korean Chemical Society
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• 제20권5호
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• pp.535-538
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• 1999

Five coordinated water-soluble iridium(l) complex, IrH(CO)(TPPTS)3 (1) (TPPTS = P(m-C6H4SO3Na)3-xH2O) has been prepared from the reaction of IrCl3·3H2O with TPPTS and HCHO in H2O/EtOH solution. Complex 1 catalyzes the hydration of nitrites (RC ≡ N, R = CH3, CICH2, CH3(CH2)4, Ph) in aqueous solution to give the corresponding amides (RCONH2) at 100℃. The hydration of unsaturated nitrites (R'C ≡ N, R'=CH3CH=CH, CH3OCH=CH, trans-PhCH=CH, CH2=C(CH3)) takes place regioselectively on-C ≡ N group to give unsaturated amides (R'CONH2) leaving the olefinic group intact. The yields of the amides seem to be depending on the electrophilicity of the carbon of nitrile: The more the electron withdrawing ability of the substituents on nitrites, the more amides are obtained. The hydration of dinitriles (NC-R-CN, R=(CH2)4, (CH2)6) with complex 1 initially gives mono-hydration products (NC-R-CONH2) which are slowly hydrated further to give dihydration products (H2NCO-R-CONH2). The hydration of 1,4-dicyanobutane has been found to be somewhat faster than that of 1,6-dicyanohexane.

• Environmental Engineering Research
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• 제20권2호
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• pp.191-197
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• 2015

The first objective of this study was to discuss the applicability of the $CO_2/CH_4$ ratio method in order to assess $CH_4$ oxidation efficiency. To achieve this objective, a comparison between $CO_2/CH_4$ ratios and the mass balance method was conducted. The second objective of this study was to estimate the $CH_4$ oxidation efficiency in an interim landfill soil cover and assess how a $CH_4$ influx influences the $CH_4$ oxidation efficiency. The results showed that despite the $CO_2$ problems brought by respiration, the $CH_4$ oxidation efficiencies obtained by the $CO_2/CH_4$ ratio method led to similar results compared to the mass balance method. In this respect, the $CO_2/CH_4$ ratio method can be an indicator of the $CH_4$ oxidation efficiencies for landfill cover soils. The $CH_4$ oxidation efficiencies derived in this study through the $CO_2/CH_4$ ratio method ranged between 46% and 64%, and between 41% and 62% through the mass balance method. The results imply that the Intergovernmental Panel on Climate Change's (IPCC) default value of 10% for the $CH_4$ oxidation efficiency is an underestimation for landfill cover soils. $CH_4$ oxidation efficiency tends to be negatively correlated with $CH_4$ influx. Therefore, $CH_4$ influx reaching a landfill cover should be limited in order to increase the $CH_4$ oxidation efficiency.

• 청정기술
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• 제16권3호
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• pp.198-205
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• 2010

염화탄화수소 열분해와 생성물분포 특성을 고찰하기 위해 등온 관형 반응기를 이용해 두 가지 실험을 수행하였다. 첫 번째는 반응분위기에 따른 열분해 특성을 파악하기 위해 $H_2$ 또는 Ar 반응분위기에서 dichloromethane ($CH_2Cl_2$) 분해율과 생성물분포 특성을 고찰하였다. Ar 반응분위기($CH_2Cl_2$/Ar 반응계)에서 보다 $H_2$ 반응분위기($CH_2Cl_2/H_2$ 반응계)에서 $CH_2Cl_2$ 분해율이 더 높았다. 이는 반응성 기체인 $H_2$ 분위기에서 $CH_2Cl_2$ 분해를 촉진시키며 수소 첨가 탈염소반응을 통해 탈염소화된 탄화수소화합물을 생성시키며, 다환방향족탄화수소 (polycyclic aromatic hydrocarbon: PAH)와 soot 생성을 억제하기 때문이다. $CH_2Cl_2/H_2$ 반응계에서 주요생성물로 탈염소화합물인 $CH_3Cl,\;CH_4,\;C_2H_6,\;C_2H_4,\;HCl$ 등이 생성되었으며, 미량 생성물로 chloroethylene이 검출되었다. $CH_2Cl_2$/Ar 반응계에서는 탄소물질수지가 낮았으며 특히 반응온도 $750^{\circ}C$ 이상에서 탄소물질 수지가 더 낮게 나타났다. 주요 생성물로는 chloroethylene과 HCl이 검출되었으며, 미량 생성물로는 $CH_3Cl$과 $C_2H_2$이 검출되었다. 고온 Ar 반응분위기에서 $CH_4$ 주입에 따른 chloroform($CHCl_3$) 분해와 생성물분포 특성을 비교 고찰하였다. $CHCl_3$ 분해율을 비교해 보면 $CH_4$을 주입할 경우($CHCl_3/CH_4/Ar$ 반응계)가 $CH_4$을 주입하지 않았을 경우($CHCl_3$/Ar 반응계)보다 분해율이 낮았다. 이는 $CHCl_3$가 분해되면서 생성되는 활성도가 큰 이중라디칼(diradical)인 :$CCl_2$가 첨가물로 주입된 $CH_4$와 반응하여 소모됨으로써 $CHCl_3$ 분해율이 상대적으로 감소되기 때문이다. Ar 반응분위기에서 $CH_4$ 첨가 여부에 따라 $CHCl_3$이 분해되면서 생성되는 생성물 분포는 큰 차이를 나타내고 있었다. 앞에서 고찰된 각 반응계에서 분해율 비교와 생성물 분포특성을 고려하고 열화학이론 및 반응속도론을 기초로 주요 반응경로를 제시하였다.

• Bulletin of the Korean Chemical Society
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• 제17권10호
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• pp.939-943
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• 1996

Reactions that proceed within mixed acetylene-methanol and ethylene-methanol cluster ions were studied using an electron-impact time-of-flight mass spectrometer. When acetylene and methanol seeded in helium are expanded and ionized by electron impact, the ion abundance ratio, [CH3OH+]/[CH2OH+] shows a propensity to increase as the acetylene/methanol mixing ratio increases, indicating that the initially ionized acetylene ion transfers its charge to adjacent methanol molecules within the clusters. Investigations on the relative cluster ion intensity distributions of [CH3OH2+]/[CH3OH+] and [(CH3OH)2H+]/[CH3OH·CH2OH+] under various experimental conditions suggest that hydrogen-atom abstraction reaction of acetylene molecule with CH3OH ion is responsible for the effective formation of CH2OH ion. In ethylene/methanol clusters, the intensity ratio of [CH3OH2]/[CH3OH] increases linearly as the relative concentration of methanol decreases. The prominent ion intensities of (CH3OH)mH over (CH3OH)m-1CH2OH ions (m=1, 2, and 3) at all mixing ratios are also interpreted as a consequence of hydrogen atom transfer reaction between C2H4 and CH3OH to produce the protonated methanol cluster ions.

• Bulletin of the Korean Chemical Society
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• 제8권3호
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• pp.179-183
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• 1987

Reactions of $Rh(ClO_4)(CO)(AsPh_3)_2$ with unsaturated nitriles and aldehyde, L, produce a series of new cationic rhodium (I) complexes, $[RhL(CO)(AsPh_3)_2]ClO_4$ (L = $CH_2$ = CHCN, $CH_2$ = C($CH_3$)CN, trans-$CH_3CH$ = CHCN, $CH_2$ = CH$CH_2$CN, trans-$C_6H_5CH$ = CHCN, and trans-$C_6H_5CH$ = CHCHD) where L are coordinated through the nitrogen and oxygen, respectively but not through the ${\pi}$-system of the olefinic group. Dissociation constants for the reaction, $[RhL(CO)(AsPh_3)_2]ClO_4$ $\rightleftharpoons$ $Rh(ClO_4)(CO)(AsPh_3)_2$ + L, have been measured to be $1.20{\times}10^{-4}$ M (L = $CH_2$ = CHCN), $1.05{\times}10^{-4}$ M (L = $CH_2$ = C($CH_3$)CN, $3.26{\times}10^{-5}$ M (L = trans-$CH_3$CH = CHCN) and $6.45{\times}10^{-5}$ M (L = $CH_2$ = CH$CH_2$CN) in chlorobenzene at $25^{\circ}C, and higher than those of triphenylphosphine complexes, $[RhL(CO)(AsPh_3)_2]ClO_4$ where L are the corresponding nitriles that are coordinated through the nitrogen atom. The differences in dissociation constants seem to be predominantly due to the differences in ${\Delta}H$ (not due to the differences in ${\Delta}S$). The weaker Rh-N (unsaturated nitriles) bonding in $AsPh_3$ complexes than in $PPh_3$ complexes (based on ${\Delta}H$ values) suggests that the unsaturated nitriles in 2∼5 are good ${\sigma}$-donor and poor ${\pi}$-acceptor.

• 한국재료학회지
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• 제21권4호
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• pp.207-211
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• 2011

Ni 8 wt.%-doped tin oxide ($SnO_2$) thick films were fabricated into gas sensors by the method of screen printing onto alumina substrates. The particle size of $SnO_2$ was controlled by changing the ball-mill time between 0~120 h. The structural and morphological properties of these thick films were investigated using X-ray diffraction and scanning electron microscopy. The structural properties of $SnO_2$ powders showed a tetragonal phase with (110) dominant orientation. The particle size of the $SnO_2$:Ni powders after ball-mill of 120 h was about 0.05 ${\mu}m$. The gas sensitivity (S = Rg/Ra) to 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas was measured at room temperature by comparing the resistance in air (Ra) with that of the target gases (Rg). The sensitivity of the $SnO_2$ gas sensors was enhanced by increasing the ball-mill time. There was an association between the sensitivity of both the $CH_4$ gas and the $CH_3CH_2CH_3$ gas and the particle size of the $SnO_2$. $SnO_2$ gas sensors prepared by 72 h ball-mill showed a sensitivity of about 13 to 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas. The response time of the $SnO_2$:Ni gas sensors to the $CH_4$ gas was about 20 seconds.