Endoscopic clipping for gastric perforation caused by excessive pulling of the tube durin PEG

류준하,윤다일,임성수,왕준호,고순영 대한내과학회 2020 대한내과학회 추계학술대회 Vol.2020 No.1

Mechanistic Analysis of 4-Methylthiobenzoyl Chloride in Solvolysis

류준하,박경호 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.4

The solvolysis mechanism of 4-methylthiobenzoyl chloride (1) was studied by kinetic methods, and these results were compared with 4-methoxy (2) and 3,4,5-trimethoxybenzoyl chlorides (3) reported previously. The analysis of kinetic data was carried out using both the simple and extended Grunwald–Winstein (G–W) equations, thermodynamic parameters, and kinetic solvent isotope effects (KSIE). In fact, 4-methylthiobenzoyl chloride (1) has a sulfur atom which is bigger in size and has more electrons than oxygen in the para-position. The results were obtained and showed typical dispersed plots from the simple (R = 0.939) and extended G–W equations (l/m = 0.33, R = 0.952) for all data, and when the data from some of the most dispersed points were removed, the correlation coefficients were improved remarkably. Thermodynamic parameters revealed that the change of enthalpies were 16.2 ~ 17.6 kJ/mol and the change of entropies were −16.5 ~ −8.6 J/K-mol. The KSIE of MeOH/MeOD was 1.42. The above results for 4-methylthiobenzoyl chloride supported a unimolecular pathway, or more precisely, a dissociated SN2 mechanism classified by l/m ratio.

Solvent Effect on the Reactions of DANSYL and BANSYL Chlorides with Substituted Pyridines

Ryu, Zoon Ha,Sung, Dae Dong,Kang, Dong Hyo,Chang, Jeong Ah,Park, Sung Bae 동의대학교 기초과학연구소 1999 基礎科學硏究論文集 Vol.9 No.1

Solvent effects on the reactions of DANSYL and BANSYL chlorides with substituted pyridines have been investigated using two parameters of Taft's solvatochromic correlation and four parameters of Kirkwood-Onsager, Parker, Marcus, Hildebrand equation. The acetonitrile molecules accelerate charge separation of the reactants and stabilize the transition state. The coefficient of the solvent parameters provide a good information to predict and to analyze the reaction mechanism. The nucleophilic substitution reaction of DANSYL and BANSYL chlorides with substituted pyridines are ruled by the contribution of the change in dipole moment term and polarity-polarizability term.

Solvolytic Reactions in Fluorinated Alcohols. Role of Nucleophilic and Other Solvation Effects

Ryu, Zoon Ha,Llewellyn, Gareth,Bentley, T. William 동의대학교 기초과학연구소 1999 基礎科學硏究論文集 Vol.9 No.1

Rate constants and products for solvolyses of chlorodiphenylmethane (Ph₂CHCl) and p-methoxybenzyl chloride in 2,2,2-trifluoroethanol (TFE)/water and TFE/ethanol are reported, along with additional kinetic data for solvolyses of tert-butyl and other alkyl halides (RX) in 97% w/w TFE/water and in 97% w/w hexafluoropropan-2-ol/water (HFIP). Results are discussed in terms of the solvent ionizing power(Y) and the solvent nucleophilicity(N), and contributions from other solvation effects are considered. Comparisons with other S_N1 solvolyses show that solvolyses of Ph₂CHCl in TFE mixtures are unexpectedly fast, but product ratios are unexceptional. An additional solvation effect influences solvolyses leading to delocalized cations, and a delocalized cationic transition state for concerted elimination may explain the recent results of Takeuchi et al., (J. Org. Chem. 1997, 62, 4904) without the need to postulate additional specific solvation effects for adamantyl systems, such as Bronsted-base solvation of α- and β-hydrogen atoms; concerted elimination may occur because simple tertiary alkyl cations are too unstable to form in predominantly aqueous media. Iodide/bromide and bromide/chloride rate ratios are very similar for 1-adamantyl halides and corresponding solvolyses of tert-butyl halides; these ratios decrease in the order aq EtOH $gt; TFE $gt; HFIP, as expected for an electrophilic solvation effect (this effect can readily be incorporated into Y values). From kinetic data for a series of tertiary alkyl chlorides in 97% TFE/water, it is shown that the susceptibility of rates of solvolyses of RCl to N decreases with an increase in steric hindrance or with an increase in charge stabilization. Also, the small kinetic solvent isotope effects for typical solvolyses (e.g., methyl tosylate) indicate that nucleophilic attack lags behind heterolysis of the C-X bond.

Methanol-1,1,2,2-Tetrachloro ethan 혼합용매계에서 치환 피리딘과 염화벤젠 술포닐의 친핵성 치환반응에 대한 속도론적 연구

옥치율,류준하 부산교육대학교 과학교육연구소 1990 科學敎育硏究 Vol.15 No.-

Kinetic studies on the nucleophilic substitution of benzenesulfonyl chloride with substituted pyridines have been conductometically carried out in 10-50(v/v)% MEOH-TCE mixtures. From the kinetic data, Hammett ρ_N values, Bro¨nsted β calues, and solvatochromic coefficients were determined caused by change in substitutents, and solvent properies. It is concluded that the reaction proceed associative S_N2 which bond formation is more advanced than bond cleavage.

성견에서 표면처리된 교정용 마미크로 임플랜트의 골 접촉률 및 동요도

박승현,김성훈,류준하,강윤구,정규림,국윤아,Park, Seung-Hyun,Kim, Seong-Hun,Ryu, Jun-Ha,Kang, Yoon-Goo,Chung, Kyu-Rhim,Kook, Yoon-Ah 대한치과교정학회 2008 대한치과교정학회지 Vol.38 No.6

The purpose of this study was to evaluate the mobility and ratio of the bone-implant contact (BIC) of a sandblasted, large grit and acid-etched (SLA) orthodontic micro-implant. Methods: Ninety-six micro-implants (48 SLA and 48 machined) were implanted in the upper and lower buccal alveolar bone, and palatal bone of four beagle dogs. Two weeks after surgery, orthodontic force (150-200 g) was applied. Two beagles were sacrificed at 4-weeks and the other two at 12-weeks. Histomorphometric comparisons were made between the SLA experimental group and the machined micro-implant as a control group to determine the ratio of contact between the bone and implant. Micro-implant mobility was also evaluated using $Periotest^{(R)}$. Results: Periotest values showed no statistically significant difference in the upper alveolar and palatal bone between groups except for the lower buccal area. BIC in the upper buccal area showed no significant difference between groups both at 4-weeks and 12-weeks. However, both the groups showed a significant difference in BIC ratio in the rest of the experimental areas between 4 weeks and 12 weeks. The experimental group showed active bone remodeling around the bone-implant interface compared to the control group. Conclusions: There were significant differences in the BIC and the Periotest values between the surface-treated and machined micro-implants according to bone quality in the early stage.

성견에서 표면처리된 교정용 마이크로임플랜트의 골 접촉률 및 동요도

박승현,김성훈,류준하,강윤구,정규림,국윤아 대한치과교정학회 2008 대한치과교정학회지 Vol.38 No.6

The purpose of this study was to evaluate the mobility and ratio of the bone-implant contact (BIC) of a sandblasted, large grit and acid-etched (SLA) orthodontic micro-implant. Methods: Ninety-six micro-implants (48 SLA and 48 machined) were implanted in the upper and lower buccal alveolar bone, and palatal bone of four beagle dogs. Two weeks after surgery, orthodontic force (150 - 200 g) was applied. Two beagles were sacrificed at 4-weeks and the other two at 12-weeks. Histomorphometric comparisons were made between the SLA experimental group and the machined micro-implant as a control group to determine the ratio of contact between the bone and implant. Micro-implant mobility was also evaluated using Periotest. Results: Periotest values showed no statistically significant difference in the upper alveolar and palatal bone between groups except for the lower buccal area. BIC in the upper buccal area showed no significant difference between groups both at 4-weeks and 12-weeks. However, both the groups showed a significant difference in BIC ratio in the rest of the experimental areas between 4 weeks and 12 weeks. The experimental group showed active bone remodeling around the bone-implant interface compared to the control group. Conclusions: There were significant differences in the BIC and the Periotest values between the surface-treated and machined micro-implants according to bone quality in the early stage. 본 연구는 비글견에 식립된 sandblasted, large grit and acid-etched (SLA) 표면처리된 교정용 마이크로임플랜트와 평활면 마이크로임플랜트에 교정력을 가한 후 시간 경과에 따른 동요도와 골접촉률의 차이를 규명하기 위해 시행되었다. 비글 성견 네 마리를 이용하여 상, 하악 협측과 구개측 골에 대해 SLA 표면처리된 표면처리군 48개, 평활면의 비처리군 48개의 마이크로임플랜트 96개를 식립하고 2주의 치유기간 후 교정력(150 - 200 g)을 지속적으로 가했으며 식립 4주 후에 두 마리를 희생시키고, 12주 후에 나머지 2마리를 희생시켰다. 표면처리군과 비처리군 간의 마이크로 임플랜트의 동요도와 골과 임플랜트 간 접촉률을 조직학적인 측면에서 측정 비교하여 다음과 같은 결과를 얻었다. 상악 협측과 구개측에서는 표면처리군과 비처리군의 동요도에서 유의성 있는 차이가 없었으나 하악협측에서는 표면처리군이 유의하게 안정적인 동요도를 보였다. 마이크로임플랜트와 인접골 간 접촉률은 상악 협측에서는 4주와 12주 모두 표면처리군과 비처리군 간에 유의한 차이가 없었으나 하악 협측과 구개측의 경우 4주와 12주 모두 표면처리군이 비처리군에 비해 유의하게 높은 접촉률을 보였다. 표면처리군은 비처리군에 비해 임플랜트 주변에서 활발한 골개조가 관찰되었으며 모든 군에서 이물반응은 관찰되지 않았다. 본 연구를 통해 SLA 표면처리된 마이크로임플랜트는 평활면 마이크로임플랜트에 비하여 식립 초기에는 식립 부위에 따라 유의하게 높은 인접골 간 접촉률과 동요도의 안정성을 보임으로써 다양한 크기와 방향의 교정력의 적용이 가능할 것이라 생각한다.

多面體 硼素化合物의 反應性과 메카니즘

成大東,金奎喆,柳俊夏,徐敬賢,金良姬 東亞大學校附設基礎科學硏究所 1990 基礎科學硏究論文集 Vol.7 No.1

1,2-dicarba-closo-dodecaborane과 carbene들과의 icosahedral carborane반응에 대한 반응성과 cage borane반응에 대한 메카니즘을 icosahedral skeleton 의 구조적 관점에서 연구하였다. 반응 생성물은 주로 B-inserted-o-carborane이였으며, B-inserted methyl-??-carborane과 di-,tri-o-carborane은 상대적으로 적게 생성되었다. B-inserted chloro-o-carborne과 carbene반응으로부터 carbone의 전자배열은 cage carborane의 구조변화에 따라 open-shell, lowest triplet 그리고 lowest closed-shell 전자배열이 유리한 것으로 나타났다. Reactivity for the reaction of icosahedral carborane, 1,2-dicarba-closo-dodecaborane with various carbenes and the mechanism for the reaction of cage borane have been studied in view point of structure of icosahedral skeleton. From Friedel-Craft reaction, the reaction products were B-inserted-0-carborane mainly and B-inserted methyl-0-carborane and di-and tri-0-carborane were produced only a little. From the carbenic reaction with B-inserted chloro-0-carboranes the electronic configurations of carbenes were favored open-shell, lowest triplet, and lowest closed-shell electronic configurations along with the structure variation of cage carboranes.

Further Kinetic Studies of Solvolytic Reactions of Isobutyl Chloroformate in Solvents of High Ionizing Power Under Conductometric Conditions

임귀택,Yeong Ho Lee,류준하 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.2

Solvolyses of isobutyl chloroformate (4) in 43 binary solvent mixtures including highly aqueous media, water, D2O, CH3OD, 2,2,2-trifluoroethanol (TFE) as well as aqueous 1,1,1,3,3,3-hexafluoro-isopropanol (HFIP) solvents were performed at 45 oC, in order to further investigate the recent results of D'Souza, M. J1. et al.; solvolyses of 4 are found to be consistent with the proposed mechanism (AdE). The variety of solvent systems was extended to comprise highly ionizing power solvent media (YCl > 2.7 excepted for aqueous fluorinated solvents and pure TFE solvent) to investigate whether a mechanistic change occurs as solvent compositions are varied. However, in case of 18-solvent ranges having aqueous fluorinated solvent systems (TFE-H2O and HFIP-H2O) and/or having YCl > 2.7 solvent systems, the solvent effect on reactivity for those of 4 are evaluated by the multiple regression analysis as competition with SN2 - type mechanism. And in pure TFE and 97 w/w % HFIP solvents with high YCl and weak NT, these solvolyses are understood as reactions which proceed through an ionization (SN1) pathway.

혼합용매에서의 용매화 (제 7 보). 등유전상수 용매에서 t-Butyl Halide 의 가용매분해반응

이익춘,이해황,엄태섭,성대동,류준하,Lee, Ick-Choon,Lee, Hai-Whang,Uhm, Tae-Seop,Sung, Dae-Dong,Ryu, Zoon-Ha 대한화학회 1988 대한화학회지 Vol.32 No.2

등유전상수 용매로 취급되는 MeOH-nitromethane, MeOH-nitrobenzene 및 MeOH-ethylene glycol 혼합용매 하에서 t-butyl halides (X = Cl, Br, I)의 가용매 분해반응을 연구 하였다. MeOH-NM 및 MeOH-NB에서 t-butyl halide의 가메탄올 분해반응 속도는 40~100 % (v/v) MeOH 조성에서 최대치를 보였다. 최대속도 현상은 용매의 극성-편극성과 수소결합 주게능력의 협력적인 결과로 설명하였다. Y값의 변화로 부터 극성-편극성과 수소 결합 주게능력의 협력적인 결과로 설명하였다. Y값의 변화로 부터 극성-편극성과 수소결합 주게능력이 기질의 반응성에 미치는 효과를 논의 하였다. E.G.에서 기질의 반응성은 MeOH에 비해 20배 이상 빠름을 보였으며 이는 아마도 E.G.의 특이한 용매구조에 기인 한다고 여겨 진다. Solvolyses of t-butylhalides (X = Cl, Br, I) in quasi isodielectric solvent system, MeOH-nitromethane, MeOH-nitrobenzene and MeOH-ethyleneglycol have been studied kinetically. Methanolyses for t-butylhalides in MeOH-NM and MeOH-NB show rate maxima at 40~100 % (v/v) MeOH. The rate maxima observed have been interpreted as a result of cooperative enhancement of polarity-polarizability and hydrogen bonddonor ability of solvents. The influences of polarity-polarizability and hydrogen bonddonor ability on reactivities of substrates have been discussed in terms of Y value changes. The solvolysis rates for t-butylhalides in E.G. are more than 20 fold faster than those in MeOH and this was attributed to the solvent structure of E.G.