• Journal of the Korean Chemical Society
• /
• v.32 no.4
• /
• pp.342-350
• /
• 1988

An experimental investigation is made to determine the mechanism of the aquation of $[Co(en)_2Cl_2]^+$ in $Hg^{2+}$ aqueous solution. The progress of reaction is followed UV/vis-spectrophotometrically by a measurment of the absorbance at a specific wavelength of Co(III) complex as a function of time. The aquation of cis-$[Co(en)_2Cl_2]^+$ and trans-$[Co(en)_2Cl_2]^+$ has been found to be first order and second order with respect to the concentration of $Hg^{2+}$ catalyst, respectively. It has been found that the reaction rate for aquation of the trans-form is faster than that of cis-form, and that the product of either cis-form or trans-form is always in the mixture ratio of 97 % to 3 %. Plausible reaction mechanism is proposed for the reaction system on the basis of kinetic data and activation parameters. Theoretical rate equation derived from the proposed mechanism is consistent with the observed one.

• The Journal of Engineering Research
• /
• v.3 no.1
• /
• pp.223-233
• /
• 1998

The kinetic and mechanism of the hydrothermal reaction between lime and quartz used solid state reaction equations have been investigated. Hydrothermal reaction on the starting materials was carried out in an autoclave that quartz mixed with calcium hydroxide in CaO/$SiO_2$ ratio of 0.8-1.0 for 0.5-8 hour at saturated steam pressure of $180-200^{\circ}C$. The rate of reaction was given from the ratio of uncombined lime and quartz content to the total lime and quartz content. The rate of reaction was obtained the results by the Jander's equation $[1-(1-\alpha)^{1/3}]^N=Kt$. The reaction of lime is controlled mainly by the dissolution such as N=1, and the reaction of quartz is controlled mostly by the diffusion such as $N\risingdotseq2$. The rate of hydrothermal reaction in the calcium silicate hydrates system is suggested to be determined generally by the mass transfer through the product laver formed around the reactant particles. The rate equation for whole hydrothermal reaction is shown that it is converted into the rate determining step by the diffusion from the boundary reaction such as approximately $N=1-2$.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.9
• /
• pp.2366-2377
• /
• 1997

An Adaptive Usage Parameter Control(UPC) mechanism using a Variable Token Pool(VTP) which is kind of preventive traffic control in the Asynchronous Transfer Mode(ATM) networks is described. The VTP mechanism can monitor violations of the average bit rate and burst duration as well as peak bit rate for the ON-OFF type traffic. The VTP can vary the token pool size by monitoring burst duration and silence duration for a long term. It also improves the sensitivity against the violation of burst duration and average bit rate and enables to response for the violating traffic situation quickly. The variable token pool size is varied in step size by every burst duration and silence duration. Two important parameters for controlling token pool size are Down_size and Up_size. We compare the performance of LB and JW mechanism with the proposed VTP mechanism by computer simulations. We have known that the proposed method is more effective than the previous mechanisms. It is shown that the cell loss rate of the VTP quite depends on the value of Down_size and Up_size. The two parameters should be decided as a propr value according to traffic situations.

• Journal of the Korean Chemical Society
• /
• v.31 no.2
• /
• pp.178-183
• /
• 1987

The kinetics of the reaction of $[Mo_3O_4(H_2O)_9]^{4+}$ with $VO_2^+$have been studied at $25^{\circ}C$ by spectrophotometric method. With$VO_2^+$ in excess, the $[Mo_3O_4(H_2O)_9]^{4+}$ reaction can be expressed as $Mo^{IV}_3+6V^V{\rightleftarrows}3Mo^{IV}+6V^IV}$. Observed rate constants for the reaction are dependent on [$H^+$] and [$VO_2^+$]. Mechanism for the redox of $[Mo_3O_4(H_2O)_9]^{4+}$and $VO_2^+$ is proposed and discussed.

• Journal of the Korean Chemical Society
• /
• v.17 no.2
• /
• pp.130-135
• /
• 1973

The rate-constants of hydrolysis of 3, 4-methylenedioxyphenylmethylenemalononitrile are determined by ultraviolet spectrophotometry at various pH and a rate equation which can be applied over wide pH range is obtained. The rate equation reveals that below pH 5.0 and above pH 9.0, the hydrolysis is initiated by the addition of water and hydroxide ion respectively. However, at pH 6.0-8.0 the competitive addition of water and hydroxide ion occurs. The catalytic contribution of hydroxide ion and water can be fully explained by the rate equation obtained.

• Journal of the Korean Chemical Society
• /
• v.20 no.6
• /
• pp.453-459
• /
• 1976

Rate constants for the reaction of methyl chloroformate with substituted anilines, and for the halogen exchanges in phenyl chloroformate have been determined in acetone. Although the rate data can be interpreted equally well with the addition-elimination mechanism($S_AN$) involving an intermediate, results of MO and isotope effect studies strongly favor the synchronous ($S_N2$) mechanism for the reactions studied. It was concluded that for the fast reacting nucleophiles the transition state is of "late" type while for the slow reacting nucleophiles it is of "early" type.

• Journal of the Korean Chemical Society
• /
• v.36 no.2
• /
• pp.180-184
• /
• 1992

Kinetic studies for the reaction of pyridine with substituted benzoyl chlorides were conducted under various pressures (1-1000 bar) in acetonitrile. From rate constants, the activation parameters (${\Delta}V^{\neq}$, ${\Delta}{\beta}^{\neq}$,${\Delta}H^{\neq}$, ${\Delta}S^{\neq}$ and ${\Delta}G^{\neq}$) were evaluated. Rates of these reaction increased with an increase in the pressure. The activation volume, the activation compressibility coefficient and the activation entropy were negative. From substituents effect and these results, it was found that these reactions proceed through $S_N2$ mechanism, but the structure of transition state was slightly changed with substituents and pressure.

• Journal of the Korean Chemical Society
• /
• v.34 no.1
• /
• pp.10-18
• /
• 1990

Solvolyses of p-substituted benzyl bromides have been studied in dimethylsulfoxide-water and N,N-dimethylformamide-water mixtures by kinetic method. To determine the ionizing power, Y and the nucleophilicity, $N_{BS}$, the solvolyses of 1-adamantyl halides, t-butyl halides, and methyl tosylate in the same solvent mixtures have been investigated. The solvatochromic parameters for each dimethylsulfoxide-water mixtures have been determined by substituting into the Taft's linear solvatochromic energy relationships with measured $ν_{max}$. The solvolyses of p-substituted benzyl bromides have been found to proceed by borderline mechanism in which bond formation is more advanced than bond cleavage in the transition state based on the m, l values and ${\beta},{\rho}_s$, values.

• 레미콘
• /
• no.10 s.73
• /
• pp.2-12
• /
• 2002

• Proceedings of the Korean Vacuum Society Conference
• /
• 1997.02a
• /
• pp.86-87
• /
• 1997