• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.487-488
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• 2008

SiOC films containing alkyl groups have a low dielectric constant because of the interaction between the C-H hydrogen bonds and the oxygen of high electro-negative atom. The Si-$CH_3$ in a void is broken by the $O_2$, therefore the strength of CH bond in Si-O-O-$CH_3$ bond increases. The Si-O-O-$CH_3$ bond is broken by nucleophilic attack due to Si atom, again. The elongation of C-H bond causes the red shift, and the compression of C-H bond causes the blue shift. Among these chemical shifts, the blue shift from $1000\;cm^{-1}$ to $1250\;cm^{-1}$ was related with the formation of pores. If the oxygen is deficient condition, the methylradicals of the electron-rich substitution group terminate easily the Si-O-Si cross-link, and the pore is originated from the cross-link breakdown due to much methyl radicals of Si-$CH_3$. The dielectric constant of the films decreases due to pore generation.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.495-500
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• 2003

The effect of initial combined load on the lateral free vibration of arches is investigated. For the analysis, P-M interaction curves for the arches are obtained. The arches are circular arches which have constant cross-section and simply supported. Also, the arches are subjected both radial uniform distributed load which results in an axial compression on the cross-section and end moments that cause uniform bending action at the same time. All analysis are performed by finite element method based on Kang and Yoo's curved beam theory.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.985-990
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• 1994

Cross-interaction constants, ${\rho}^e_{XY}$, ${\rho}_{YZ}$ and ${\rho}_{XZ}$ are defined using observed rate constant, k_N=(k_1/k_{-1})k_2=Kk_2$, for the stepwise carbonyl addition reactions involving the rate-limiting breakdown of a tetrahedral intermediate $(T^{\pm})$. Abundant experimental evidence in the literature enables us to determine signs for the three constants for such mechanism, ${\rho}^e_{XY}$>0, ${\rho}_{YZ}$<0 and ${\rho}_{XZ}$0. These are in contrast to those for the concerted $S_N2$ mechanism, ${\rho}_{XY}$<0, ${\rho}_{YZ}$>0 and ${\rho}_{XZ}$, and provide useful mechanistic criteria. In the light of these criteria, mechanisms of some nucleophilic reactions of carbonyl compounds are re-examined.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1579-1582
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• 2009

The reaction rates of 4-X-2,6-dinitrochlorobenzenes (X = $NO_2,\;CN,\;CF_3$) with Y-substituted pyridines (Y = 3-$OCH_3,\;H,\;3-CH_3,\;4-CH_3$) in methanol-acetonitrile mixtures were measured by conductometry at 25 ${^{\circ}C}$. It was observed that the rate constant increased in the order of X = 4-$NO_2\;>\;4-CN\;>\;4-CF_3$ and the rate constant also increased in the order of Y = 4-$CH_3\;>\;3-CH_3\;>\;H\;>\;3-OCH_3$. When the solvent composition was varied, the rate constant increased in order of MeCN > 50% MeOH > MeOH. The electrophilic catalysis by methanol may be ascribed to the formation of hydrogen bonds between alcoholic hydrogen and nitrogen of pyridines in ground state. Based on the transition parameters, ${\rho}_S,\;{\rho}_N,\;{\beta}_Y,\;{\rho}_{XY}$ and solvent effects, the reaction seems to proceed via $S_N$Ar-Ad.E mechanism. We also estimated the isokinetic solvent mixtures (${\rho}_{XY}$ = 0) based on cross-interaction constants, where the substituent effects of the substrate and nucleophile are compensated.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1217-1220
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• 2007

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.753-757
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• 2014

The nucleophilic substitution reactions of Y-aryl N,N-dimethyl phosphoroamidochloridates with substituted anilines and deuterated anilines are kinetically investigated in acetonitrile at $65.0^{\circ}C$. A stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed based on the positive ${\rho}_{XY}$ value. The deuterium kinetic isotope effects involving deuterated anilines show secondary inverse with all the nucleophiles, rationalized by a dominant backside nucleophilic attack.

• Bulletin of the Korean Chemical Society
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• v.19 no.12
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• pp.1334-1336
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• 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.

• International Journal of High-Rise Buildings
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• v.13 no.1
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• pp.85-95
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• 2024

A composite member made of concrete-filled steel tubes (CFT columns) has been recognized for its fire resistance due to the thermal mass effect of concrete inside the steel tube, as shown in various studies. In this study, the fire resistance performance of reinforced CFT columns under constant axial load was evaluated using finite element analysis with ABAQUS. For this purpose, the variables including cross-section size, steel tube thickness, and concrete cover thickness were set, and the temperature distribution in the column cross-section exposed to a standard fire was investigated using heat transfer analysis. Ultimately, a P-M interaction curve was obtained by evaluating the overall residual strength of columns, and the fire resistance time was determined by evaluating axial displacement-time responses due to the reduction in load capacity during fire through stress analysis.

• Bulletin of the Korean Chemical Society
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• v.27 no.5
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• pp.733-738
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• 2006

Nucleophilic addition reactions of p-substitutedbenzylamines $(XC _6H_4CH _2NH _2)$ to $\alpha$-phenyl-$\beta$-thiophenyl-acrylonitriles ($YC _4SH _2CH=C(CN)C_6H_4$Y') have been studied in acetonitrile at 25.0, 30.0, and 35.0 ${^{\circ}C}$. The reactions take place in single step in which the $C_\beta$ -N bond formation and proton transfer to $C_\alpha$ of $\alpha$-phenyl-$\beta$-thiophenylacrylonitriles occur concurrently with four-membered cyclic transition structure. These mechanistic conclusions are drawn based on (i) the large negative $\rho$x and large positive $\rho$Y' values and also large magnitude of $\rho$X, (ii) the negative sign and large magnitude of the cross-interaction constants ($\rho$XY), (iii) the normal kinetic isotope effects ($k_H/k_D$ > 1.0), and (iv) relatively low $\Delta H ^\neq$ and large negative $\Delta S ^\neq$ values.

• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1670-1674
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• 2007

Addition reactions of anilines (XC6H4NH2) to β-nitrostilbene (YC6H4CH=C(NO2)C6H4Y') have been investigated in acetonitrile at 30.0 oC. The magnitude of βX values (=0.11-0.34) indicates relatively earlier transition state for additions with anilines than with benzylamines. The signs of ρY and ρY' are positive with Δρ = ρY?ρY' = 0.04, demonstrating a TS imbalance with a negative charge development on the Cβ in the TS. The signs of cross-interaction constants ρXY (<0), ρXY' (<0) and ρYY' (>0) are consistent with bond forming and breaking processes. The relatively weak normal kinetic isotope effects involving deutarated nucleophiles, kH/kD>1, suggest an early, hydrogen-bonded, 4-member cyclic TS.