• Bulletin of the Korean Chemical Society
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• 제13권2호
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• pp.166-172
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• 1992

Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethoxyalkyl)phthalimides(alkyl=E thyl, n-propyl, n-butyl, n-pentyl, and n-octyl). Photocyclizations occur in methanol in high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from oxygen in the $\alpha-silylmethoxy$ groups to the singlet excited state phthalimide moieties followed by desilylation of the intermediate $\alpha-silylmethoxy$ cation radicals and cyclization by radical coupling are proposed. In contrast, photoreaction of N-(trimethylsilylmethoxyethyl) phthalimide in acetone follows different reaction routes to produce two cyclized products in which carbon-carbon bond formation takes place between the phthalimide carbonyl carbon and the carbon $\alpha$ to silicon and oxygen atoms via triplet carbonyl hydrogen abstraction triplet carbonyl silyl group abstraction pathways. The normal singlet SET pathway dominates these triplet processes for photoreaction of this substance in methanol. The efficient and regioselective cyclization reactions observed for photolysis in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.

• Carbon letters
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• 제2권1호
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• pp.22-26
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• 2001

Na alloyed graphite intercalation compounds with stage 1 and 2 were synthesized using the high temperature and pressure technique. Thermal stability and staging transitions of the compounds were investigated depending on heating rates. The thermal stability and temperature dependence of the deintercalation compounds were characterized using differential scanning calorimeter (DSC) analyzer. Enthalpy of formations were confirmed at temperatures between 25 and $500^{\circ}C$, depending on the various heating rates. The structure ions and interlayer spaces of the graphite were identified by X-ray diffraction (XRD). Diffractograms of stages with non-integral (00l) values were obtained in the thermal decomposition process, and stacking disorder defects and random stage modes were observed. The average value of the interlayer C-C bond lengths were found approximately $2.12{\AA}$ and $1.23{\AA}$ from the diffractions. Based on the stage transition, the degree of the deintercalaton has a inverse-linear relationship against the heating rate.

• 대한화학회지
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• 제19권2호
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• pp.116-122
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• 1975

Benzyl arenesulfonate와 피리딘과의 아세톤 용매중에서의 反應速度를 測定하였다. Benzyl arenesulfonate의 離脫基의 치환기효과는 p-MeO基 및 $p-NO_2$기를 除外하고는 Hammett 式에 잘 적용되었으며, 전자끄는기는 반응속도를 증가시켰다. 離脫基의 치환효과는 벤질炭素에 아민이 親核的으로 공격하여 전이상태에서 치환기의 電子끄는 능력이 C-N 結合의 形成과 C-O結合의 쪼개짐에 변화를 주고 있다는 사실로서도 설명이 되어진다. 치환기효과는 benzyl p-bromobenzeneslfonate가 benzyl p-nitrobenzenesulfonate보다 N-C結合이 tight 한 전이상태의 구조를 가지고 있음을 말해주며 이는 結合의 형성과 쪼개짐에 있어 Thornton의 $S_N2$전이상태 구조의 예상과도 잘 符合된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.426-427
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• 2007

Here we describe the formation of a self-assembled film of thin multiwalled carbon Nanotubes(t-MWNT) modified with hydroxy groups through hydrogen peroxide treatment. Morphologies of t-MWNT films could be controlled by the various coating method, such as filtering, drop casting, spraying method, etc. The results show that on densification of the CNT suspension during drying, multiple hydroxy group-modified MWNTs can be self-assembled through strong surface hydrogen bond interaction while MWNTs usually exist an entangled state in the film. The interaction between t-MWNT was illustrated from Raman spectrum of spray coated films.

• Bulletin of the Korean Chemical Society
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• 제1권2호
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• pp.62-68
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• 1980

Ultraviolet spectrophotometric investigations have been carried out the systems of monoalkylbenzene with iodine in carbon tetrachloride. The results reveal the formation of one to one molecular complexes. The equilibrium constants for these complexes of representative monosubstituted benzene reveal the following order of increasing stability: benzene < methyl- < ethyl- < n-propyl-benzene. The value of ${\Delta}H$, ${\Delta}G$, and ${\Delta}S$ for interaction of a number of monoalkyl substituted benzene with iodine has been determinated. In general, as ΛH becomes increasingly negative, corresponding decreases in ${\Delta}G$ and ${\Delta}S$ values are observed, and these variation are linear. The thermodynamic constants become increasingly negative with increasing monoalkyl substitution of the aromatic donor nucleus. The complex bond is therefore weak, and its formation is accompanied by relatively small entropy changes.

• Nano
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• 제13권10호
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• pp.1850116.1-1850116.14
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• 2018

In this study, we report the mercury ions ($Hg^{2+}$) mediated phosphorus-containing carbon dots (PCDs) as a selective "off-on" fluorescence probe for glutathione (GSH), cysteine (Cys) and homocysteine (Hcys). PCDs obtained by hydrothermal reaction are sensitive to $Hg^{2+}$ ions and its fluorescence can be significantly quenched owing to the electron transfer from the lowest unoccupied molecular orbital (LUMO) of PCDs to $Hg^{2+}$. Interestingly, the weak fluorescence of $Hg^{2+}$-mediated PCDs could be gradually recovered with the addition of GSH, Cys and Hcys. This can be attributed to the formation of $Hg^{2+}-S$ complex due to the super affinity of $Hg^{2+}$-sulfydryl bond. The formation of $Hg^{2+}-S$ complex extremely reduces the oxidation ability of $Hg^{2+}$ that inhibits the electron transfer from LUMO of PCDs to $Hg^{2+}$ and re-opens the native electron transition from LUMO to the highest occupied molecular orbital (HOMO) of PCDs. Thus, the green fluorescence of PCDs is switched on. Furthermore, the present $Hg^{2+}$-mediated PCDs assay exhibits a high selectivity for GSH, Cys and Hcy and has been successfully used to detect the total biothiols content in human urine samples.

• Corrosion Science and Technology
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• 제16권2호
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• pp.69-75
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• 2017

Zinc coating on carbon steels give the higher corrosion resistance in chloride containing environments and in carbonated concrete. However, hydrogen evolution accompanies the corrosion of zinc in the initial activity in fresh concrete, which can lead to the formation of a porous structure at the reinforcement -concrete interface, which can potentially reduce the bond-strength of the reinforcement with concrete. The present study examines the mechanism of the corrosion of hot-dip galvanized steel in detail, as in the model pore solutions and real concrete. Calcium ion plays an important role in the corrosion mechanism, as it prevents the formation of passive layers on zinc at an elevated alkalinity. The corrosion rate of galvanized steel decreases in accordance with the exposure time; however, the reason for this is not the zinc transition into passivity, but the consumption of the less corrosion-resistant phases of hot-dip galvanizing in the concrete environment. The results on the electrochemical tests have been confirmed by the bond-strength test for the reinforcement of concrete and by evaluating the porosity of the cement adjacent to the reinforcement.

• 한국태양에너지학회 논문집
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• 제30권5호
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• pp.11-16
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• 2010

Methane hydrate is crystalline ice-like compounds which formed methane gas enters within water molecules composed cavity and each other from physically-bond at specially temperature and pressure condition. $1m^3$ of methane hydrate can be decomposed into the maximum of $216m^3$ of methane gas under standard condition. If these characteristics of hydrate are utilized in the opposite sense, natural gas can be fixed into water in the form of a hydrate solid. Therefore the use of hydrate is considered to be a great way to transport and store natural gas in large quantity. However, when methane hydrate is formed artificially, the amount of gas that is consumed is relatively low, due to the slow reaction rate between water and methane gas. Therefore for practical purposes in the application, the present investigation focuses on increasing the amount of gas consumed by adding chemically oxidized OMWCNTs to pure water. The results show that when 0.003 wt% of oxidation multi-walled carbon nanotubes was added to pure water, the amount of gas consumed was almost four times more than that of pure water indicating its effect in hydrate formation and the hydrate formation time decreased at alow subcooling temperature.

• 대한방사성의약품학회지
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• 제4권1호
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• pp.16-21
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• 2018

Organoboron compounds and their derivatives are synthetically versatile building blocks because they are readily available, stable, and highly useful for potential organic transformations. Arylboronic esters are of particular interest due to their well-established synthetic methods: transition metal catalyzed borylations of aryl halides. However, the use of aryl halides as an electrophile has one serious disadvantage: formation of toxic halogenated byproducts. A promising alternative substrate to aryl halides would be phenol derivatives such as aryl ethers, esters, carbamates and sulfonates. The phenol derivatives involve several advantages: their abundance, relatively low toxicity and versatile synthetic application. However, utilization of the aryl methyl ether, which is one of the simplest phenol derivatives, remains as a challenge, as C-OMe bond activation requires high activation energy and methoxides are not good leaving groups. Nevertheless, there have been a significant recent progress on ipso-borylation of aryl methyl ether including Martin's nickel catalysis. Here, we review the current advance on the borylation of carbon-oxygen bonds of unactivated C-OMe bond in aromatic compounds.

• 전기화학회지
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• 제3권2호
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• pp.85-89
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• 2000

Lithium ion Battery(LIB)의 음극 활물질로써 리튬을 대체하기 위한 노력으로 phenol resin을 탄화시킨 탄소재료를 사용하였다. Phenol resin을 소성하면 축합반응을 일으키면서 탄화되어 무정형 탄소가 된다. 무정형 탄소는 층간거리가 넓어 리튬의 삽입과 탈리가 용이하지만 탄소간의 결합력이 약하여 구조적 붕괴가 일어난다. 이러한 문제를 해결하기 위해 세공형성제로서 $ZnCl_2$를 사용하였다. $ZnCl_2$는 생성된 물질에서 3차원적 망상구조로 성장하는 개방세공을 형성하는 세공형성제로서 뿐만 아니라, 벌크 첨가제가 도핑된 느슨한 구조를 형성하는 미세세공 형성제로서 작용하였다. SEM을 통해서 구조적 차이를 알 수 있었으며, XRD분석으로 층간의 거리를 알 수 있었다. CV측정을 통해 두 가지 샘플에 대한 산화와 환원 반응의 차이를 알아보았다.