• Bulletin of the Korean Chemical Society
• /
• 제19권10호
• /
• pp.1084-1090
• /
• 1998

The oxidation of triphenylphosphine by [(tpy)(phen)RuⅣ(O)]2+ and [(bpy)(p-tert-butylpy)RuⅣ(0)]2+ (tpy is 2,2': 6',2"-terpyridine, phen is 1,10-phenanthroline, bpy is 2,2'-bipyridine, and p-tert-butylpy is para-tertbutylpyridine) in CH3CN has been studied. Experiments using 18O-labeled complex show the oxyl group transfer from [RuⅣ=O]2+ to triphenylphosphine occured quantitatively within experimental error. Kinetic data were fit to a second-order for [RuⅣ=O]2+ and [PPh3]. The initial product, [RuⅡ-OPPh3]2+, was formed as an observable intermediate and then underwent slow solvolysis. The reaction proceeded as endothermic in activation enthalpy and a decrease in activation entropy. The oxidative reactivity of four representative ruthenium mono-oxo oxidants against triphenylphosphine was compared. These systems have been utilized as electrochemical oxidative catalysts.

• 대한설비공학회지:설비저널
• /
• 제16권5호
• /
• pp.477-483
• /
• 1987

A FORTRAN code has been developed to calculate thermodynamic properties of 12 kinds of refrigerants. Input variables are temperature and pressure or temperature only depending on the saturation. The program output properties are specific volume, saturation pressure, enthalpy, entropy, specific heats and speed of sound. Sample calculations show that output properties are in very good agreements with thermodynamic tables and charts.

• 설비공학논문집
• /
• 제2권3호
• /
• pp.218-225
• /
• 1990

Studies on the performance of a heat pump using non-azeotropic refrigerant mixtures are done. In order to estimate the thermodynamic properties for the selected non-azeotropic refrigerant mixtures including R22/R152a, R22/R142b, R22/R114 and R13B1/R152a, Peng-Robinson equation of state is adopted. The pressure-enthalpy diagram and the temperature-entropy diagram are plotted for each refrigerant mixture. Considerations on the capacity modulation for the heat pump system using refrigerant mixtures are taken into. Results show that when the heating load varies, the possibility for the capacity modulation is found in the heat pump system using a compressor with constant volume flow rate. Under a constant heating capacity condition in the heat pump system, the coefficient of performance increases when the refrigerant mixtures are used. The volume flow rate decreases as the mass fraction of lower boiler increases in this case.

• Journal of Photoscience
• /
• 제12권3호
• /
• pp.113-117
• /
• 2005

Spectroscopic investigations on the interaction of gabapentin (GBP) with bovine serum albumin (BSA) were reported. The association constant of GBP-BSA system was determined at different temperatures (298, 302, 306 and 311 K) based on the fluorescence quenching results. The GBP was found to quench the fluorescence of BSA through static mechanism. Thermodynamic parameters, the standard enthalpy change, $({\Delta}H^o)$ and the standard entropy change $({\Delta}S^o)$ were observed to be $-9.61{\pm}0.008\;kJ\;mol^{-1}$ and $3.58{\pm}0.011\;Jmol^{-1}K{-1}$ respectively. These indicated that the hydrophobic and electrostatic forces played a role in the interaction of GBP with BSA. The negative value of ${\Delta}G^o$ revealed that the binding reaction is spontaneous. The circular dichroism studies indicated the conformational changes in BSA upon interaction with GBP. The effect of some metal ions on the binding constant was also investigated.

• 한국세라믹학회지
• /
• 제45권7호
• /
• pp.375-379
• /
• 2008

Redox behavior was observed in alkali alkaline earth silicate PDP (Plasma Display Panel) glass melts doped with sulfate and sulfide by square wave voltammetry (SWV). According to voltammograms produced at a temperature range of 1100 to $1400^{\circ}C$ and frequency range of 5 to 1000 Hz, both melts showed the same behavior in which there is one reduction peak at low frequency but another peak at an increase of frequency. Based on the frequency dependence of the peak current, self diffusivity of $S^{4+}$ was determined. Based on the temperature dependence of the peak potential, standard enthalpy (${\Delta}H^0$) and standard entropy (${\Delta}S^0$) for the reduction of $S^{4+}$ to $S^0$ were calculated.

• 한국응용과학기술학회지
• /
• 제6권1호
• /
• pp.67-73
• /
• 1989

The adsorptions of 2-(dimethylalkylammonio)propanoates with straight chain alkyl group having from 12 to 16 carbon atoms on the liquid-air interface were decreased while lowering the surface tensions at critical micelle concentrations. In micellization, the standard free energy changes per methylene in alkyl group were found to make same contribution to the micelle formation of corresponding C-alkylcarboxybetaines, and the standard enthalpy and entropy changes were studied within the range of temperature from 30 to $50^{\circ}C$.

• Bulletin of the Korean Chemical Society
• /
• 제4권5호
• /
• pp.212-217
• /
• 1983

Depending on the range of shear rates, temperatures and concentrations, the potato starch suspension in water behaves as a typical dilatant system. The flow curves of the suspension at various concentrations and temperatures were obtained by using a Couette type rotational viscometer. The flow mechanism of the suspension is explained by a structure model of starch granules in the suspension. Based on the experimental results, a general flow equation for the dilatant system is proposed. By analyzing the temperature dependency of the relaxation time, the activation enthalpy and activation entropy for flow in the starch-water suspension were calculated, the former being about 10 kcal/mol.

• 대한화학회지
• /
• 제35권2호
• /
• pp.135-141
• /
• 1991

N,N'-oxalylbis(salicylaldehyde hydrazone) (OBSH)과 Zn (II), Cd (II) 및 Pb(II) 이온들과의 착물 형성에 따르는 안정도상수를 DMSO 용액에서 폴라로그래피법으로 측정하였다. 안정도상수의 크기는 Cd(II) < Zn(II) < pb(II) 이온의 순서로 증가하였으며, 모든 중금속이온들의 OBSH 리간드와 매우 안정한 착물을 형성하였다. 안정도상수를 여러 온도에서 측정하여 엔탈피 및 엔트로피 변화를 구한 결과, 착물의 안정도에 많은 기여를 하고 있음을 알았다.

• 해양환경안전학회지
• /
• 제14권2호
• /
• pp.145-148
• /
• 2008

화장품과 유처리제 등에 응용할 수 있는 양이온 계면활성제인 N-octadecyl pyridinium bromide를 사용하여 온도 $40{\sim}60^{\circ}C$ 범위에서 적하법을 이용한 임계미셀농도를 적용 미셀형성에 따른 열역학적 특성(자유에너지, 엔탈피, 엔트로피, 열용량)을 조사하였다. 그 결과 자유에너지 변화는 온도가 증가함에 따라 감소함을 알 수 있었다.

• 대한화학회지
• /
• 제63권4호
• /
• pp.233-236
• /
• 2019

In this study, the solvolysis of cyclohexanesulfonyl chloride (1) was studied by kinetics in ethanol-water, methanol-water, acetone-water, and 2,2,2-trifluoroethanol (TFE)-water binary solvent systems. The rate constants were applied to the extended Grunwald-Winstein equation, to obtain the values of m = 0.41 and l = 0.81. These values suggested $S_N2$ mechanism in which bond formation is more important than bond breaking in the transition state (TS). Relatively small activation enthalpy values (11.6 to $14.8kcal{\cdot}mol^{-1}$), the large negative activation entropy values (-29.7 to $-38.7cal{\cdot}mol^{-1}{\cdot}K^{-1}$) and the solvent kinetic isotope effects (SKIE, 2.29, 2.30), the solvolyses of the cyclohexanesulfonyl chloride (1) proceeds via the $S_N2$ mechanism.