• Bulletin of the Korean Chemical Society
• /
• 제21권9호
• /
• pp.901-904
• /
• 2000

The mechanism for the photo-Fries rearrangement of phenyl acetate andbiphenylyl acetates were reinvestigat-ed in phenol (or phenol derivatives) containing media. The results showed that the phenol (or phenol deriva-tives) which is the most common by-product of Fries reaction reacts with acyl radical togive Fries-product. These phenol (or phenol derivatives) contributions to the Fries-products were suggested as the Trivial mecha-nism for the photo-Fries reaction.

• Bulletin of the Korean Chemical Society
• /
• 제19권4호
• /
• pp.434-436
• /
• 1998

The mechanism of nucleophilic displacement was studied by using three variable systems of ${\rho}_X,\; {\rho}_Y,\; and {\rho}_Z$ obtained from the change of substituent X, Y, and Z for the reaction of (Z)-substituted benzyl (X)-benzensulfonates with (Y)-substituted thiobenzamides in acetone at 45 ℃. The results ${\rho}_Z$<0 and ${\rho}_YZ$>${\rho}_XZ$ indicate that this reaction series proceeded via a dissociative $S_N2$ mechanism. The prediction of the movement of TS by using the sign of ${\rho}_XZ{\cdot}{\rho}_{YZ}$ accorded with the Hammond postulate.

• Bulletin of the Korean Chemical Society
• /
• 제13권5호
• /
• pp.504-507
• /
• 1992

fac-RuH(NO)(ttp) is fluxional in the range between 180 K and 303 K. The structures involved in this fluxional process are found to be a mixture of two square pyramids and a trigonal bipyramid from the low temperature NMR spectra and the line shape analysis using DNMR 3 program and the activation parameters of this process were determined by using the simulated data. The mechanism of this fluxional process is proposed to be a pathway known as Turnstile Rotation.

• Bulletin of the Korean Chemical Society
• /
• 제18권12호
• /
• pp.1301-1304
• /
• 1997

Elimination reactions of (E)-2,4-dinitrobenzaldehyde O-pivaloyloxime promoted by R2NH/R2NH2+ buffer in 70% MeCN(aq) have been studied kinetically. The reaction exhibited second order kinetics and general base catalysis with Bronsted β=0.45. The Hammett ρ value decreased from 2.3 to 1.6 as the base-solvent system was changed from DBU in MeCN to R2NH/R2NH2+ buffer in 70% MeCN(aq). From these results an E2 mechanism is proposed.

• Bulletin of the Korean Chemical Society
• /
• 제19권12호
• /
• pp.1334-1336
• /
• 1998

Kinetic studies are carried out on the reactions of 2-chloro-2-propen-1-yl arenesulfonates with anilines and N,N-dimethylanilines in acetonitrilile at 45.0 ℃. The 2-chloro substituent is found to deactive the allyl moiety with considerable decrease in the rates. The sign and magnitude of the cross-interaction constant (ρxz 0.3) and the inverse secondary kinetic isotope effect (kH/kD 0.92) support an SN2 mechanism with a relatively tight transition state. The possibility of an SN2' mechanism can be safely precluded based on the ρxz values observed.

• Bulletin of the Korean Chemical Society
• /
• 제16권7호
• /
• pp.657-661
• /
• 1995

Kinetic studies are carried out on the reaction of S-phenyl dithiobenzoates with benzylamines in acetonitrile at 30.0 ℃. Small magnitude of ρX (βX) as well as ρZ (βZ) obtained suggests rate-limiting nucleophilic attack of the thiocarbonyl carbon. This is supported by the unusually small magnitude of ρXY and ρYZ, albeit their signs do not agree with those expected. Moreover, the inverse secondary kinetic isotope effects (kH/kD<1.0) involving deuterated benzylamine nucleophiles are also in line with the proposed mechanism.

• 한국자동차공학회논문집
• /
• 제16권6호
• /
• pp.74-80
• /
• 2008

A combustion of CAI engine is purely dominated by fuel chemical reactions. In order to simulate the combustion of CAI engine, it should be considered the effect of fuel components and chemical kinetics. So it needs enormous computational power. To overcome this problem reduced problem of needing massive computational power, chemical kinetic mechanism and multi-zone method is proposed here in this paper. A reduced chemical kinetic mechanism for a gasoline surrogate was used in this study for a CAI combustion. This gasoline surrogate was modeled as a blend of iso-octane, n-heptane, and toluene. For the analysis of CAI combustion, a multi-zone method as combustion model for a CAI engine was developed and incorporated into the computational fluid dynamics code, STAR-CD, for computing efficiency. This coupled multi-zone model can calculate 3 dimensional computational fluid dynamics and multi-zoned chemical reaction simultaneously in one time step. In other words, every computational cell interacts with the adjacent cells during the chemical reaction process. It can enhance the reality of multi-zone model. A greatly time-saving and yet still relatively accurate CAI combustion simulation model based on the above mentioned two efficient methodologies, is thus proposed.

• 대한화학회지
• /
• 제20권3호
• /
• pp.236-239
• /
• 1976

광독성 물질인 쿠마린과 푸로쿠마린의 광화학반응을 분광분석, 삼중상태 켄칭, 형광법을 써서 연구하였다. 크산토톡신과 티민 또는 DNA 수용액의 광화학반응에서 ${\beta}$-카로텐을 켄치로 썼으나 아무런 켄칭이 일어나지 않는 것으로 보아 이 반응은 수명이 긴 크산토톡신의 삼중상태보다 수명이 짧은 들뜬 단일상태에서 일어나는 것으로 생각된다.

• Membrane and Water Treatment
• /
• 제9권5호
• /
• pp.353-361
• /
• 2018

Fouling characteristics of humic substances on tight ultrafiltration (UF) membrane have been investigated. The tight UF membrane was prepared by blending polysulfone (PSf) in N.N-dimethylacetamide (DMAc) with 25%wt of Polyethylene glycol (PEG400) and 4%wt of acetone. Fouling characteristic of the modified PSf membrane was observed during peat water filtration in different trans-membrane pressure (TMP). It was found that the acetone modified membrane provided 13% increase in TMP during five hours of peat water filtration, where a stable flux was reached within 150 minutes. Meanwhile, the increase of TMP from 10 psig to 30 psig resulted in a fouling resistance enhancement of 60%. Furthermore, based on the fouling analysis, fouling mechanism at the first phase of filtration was attributed to intermediate blocking while the second phase was cake formation.

• Membrane and Water Treatment
• /
• 제7권4호
• /
• pp.327-339
• /
• 2016

Nanofiltration is useful to concentrate propolis extract. During the selection of membrane, both compound rejection and permeate flux are important indicators of process economy. Brazilian green propolis extract was studied to evaluate the separation performance of Startmen 122 and NF270 membranes. Compared to Starmen 122, NF270 membrane showed better rejection of bioactive compounds. The flux decline patterns were further studied using Hermia's model. Cake formation is the major fouling mechanism on the hydrophobic surface of Starmen 122. While the fouling mechanism for NF270 is pore blocking. The fouled membranes were further characterized using SEM and FT-IR to confirm on the predicted fouling mechanisms.