• Bulletin of the Korean Chemical Society
• /
• v.29 no.2
• /
• pp.319-322
• /
• 2008

The viability of acetylene addition in each step of aromatic formation initiated by vinyl radical and acetylene also with its competition with structure rearrangement is investigated by determining optimal geometries and barrier and reaction energies using quantum mechanical methods. In principle, the addition reaction has more difficult in term of free energy and enthalpy compared to geometry arrangement. Under combustion conditions, i.e. T = 1200 K, acetylene addition is unfavorable mechanism as the barrier energy values rise much higher than that of geometry arrangement. However, in longer chain hydrocarbon case, e.g. n-CxHx+1 where x ³ 8, C-C bond rotation is rather difficult and requires high energy to form a ring structure, elongation chain is preferable.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.8
• /
• pp.1231-1237
• /
• 2004

Rate constants for photolytic reactions of p-substituted 2-diazopropiophenones were determined in acetonitrile. The reactions show a comparatively low value of activation energy and activation enthalpy to alkylcarbenes or other arylcarbenes. The transition state corresponds to the step of a new carbonyl bond formation. The high negative ρ -values are shown in Hammett plots. The kinetics results and EPR spectrum are in accord with a phenomenon that occurs in interconversion between singlet and triplet carbenes.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.1
• /
• pp.53-58
• /
• 1995

Heats of solution of aniline (AN), benzylamine (BA), ethyl-(EBS) and 2-phenylethyl benzenesulfonates (PEB) are calorimetrically measured in acetonitrile-methanol mixtures at 25.0 $^{\circ}C$. The activation parameters, ${\Delta}H^{\neq}$, ${\Delta}S^{\neq}$ and ${\Delta}G^{\neq}$, are determined for the reactions of EBS and PEB with AN and BA using the kinetic data at three temperatures. Calorimetric transfer enthalpies of initial state, ${\delta}H_t^{0{\rightarrow}x})$(IS), and kinetically derived activation enthalpies, ${\delta}\;{\Delta}H^{\neq}$, in the MeCN-MeOH mixtures are combined to determine the transfer enthalpies of transition state, ${\delta}H_t^{0{\rightarrow}x})$(TS); ${\delta}H_t^{0{\rightarrow}x})$(IS) = ${\delta}{\Delta}H^{\neq}\;+\;{\delta}H_t^{0{\rightarrow}x}$(IS) The preferential solvation of anionic charge in the TS predicts a loose TS with a greater degree of bond cleavage for the reactions of PEB than for EBS, and also for the reactions with BA compared to the reactions with AN.

• Advances in nano research
• /
• v.13 no.2
• /
• pp.121-134
• /
• 2022

Emerge of nanotechnology impacts all aspects of humans' life. One of important aspects of the nanotechnology and nanoparticles (NPs) is in the food production industry. The safety of such foods is not well recognized and producing safe foods using nanoparticles involves delicate experiments. In this study, we aim to incorporate intelligent computer simulation in predicting safety degree of nanofoods. In this regard, the safety concerns on the nano-foods are addressed considering cytotoxicity levels in metal oxides nanoparticles using adaptive neuro-fuzzy inference system (ANFIS) and response surface method (RSM). Three descriptors including chemical bond length, lattice energy and enthalpy of formation gaseous cation of 15 selected NPs are examined to find their influence on the cytotoxicity of NPs. The most effective descriptor is selected using RSM method and dependency of the toxicity of these NPs on the descriptors are presented in 2D and 3D graphs obtained using ANFIS technique. A comprehensive parameters study is conducted to observe effects of different descriptors on cytotoxicity of NPs. The results indicated that combinations of descriptors have the most effects on the cytotoxicity.

• The Korean Journal of Food And Nutrition
• /
• v.15 no.4
• /
• pp.331-336
• /
• 2002

Conformation of soymilk protein was examined to obtain basic information for improved calcium intolerence of soymilk protein partially hydrolyzed with protease. Surface hydrophobicities of three proteins showed the order of SMP(soymilk protein) < SPI(soy protein isolate) < PT-SMP(protease treated soymilk protein). Total thiol group contents of SMP and PT-SMP were similar but larger than that of SPI. Reducing rate of disulfide bond in PT-SMP after 2-mercaptoethanol treatment was laster than that in SMP. And so, this result indicates that PT-SMP may be less compacting due to protease treatement. From circular dichroism result, PT-SMP showed different pattern from SMP and SPI suggesting change of secondary structure by hydrolysis. And analysis of heat denaturating property by DSC showed that denaturation enthalpy of three proteins were all small. Especially enthalpy of PT-SMP was least, and this result suggested that PT-SMP was denatured easily by heating due to less compacting structure.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.3
• /
• pp.810-814
• /
• 2013

The thermodynamic parameters for the intercalative interaction of structurally related well known intercalators, 9-aminoacridine (9AA) and proflavine (PF) were determined by means of fluorescence quenching study. The fluorescence intensity of 9AA decreased upon intercalation to DNA, poly[$d(A-T)_2$] and poly[$d(G-C)_2$]. A van't Hoff plot was constructed from the temperature-dependence of slope of the ratio of the fluorophore in the absence and presence of a quencher molecule with respect to the quencher concentration, which is known as a Stern-Volmer plot. Consequently, the thermodynamic parameters, enthalpy and entropy change, for complex formation was calculated from the slope and y-intercept of the van't Hoff plot. The detailed thermodynamic profile has been elucidated the exothermic nature of complex formation. The complex formation of 9AA with DNA, poly[$d(A-T)_2$] and poly[$d(G-C)_2$] was energetically favorable with a similar negative Gibb's free energy. On the other hand, the entropy change appeared to be unfavorable for 9AA-poly[$d(G-C)_2$] complex formation, which was in contrast to that observed with native DNA and poly[$d(A-T)_2$] cases. The equilibrium constant for the intercalation of PF to poly[$d(G-C)_2$] was larger than that to DNA, and was the largest among sets tested despite the most unfavorable entropy change, which was compensated for by the largest favorable enthalpy. The favorable hydrogen bond contribution to the formation of the complexes was revealed from the analyzed thermodynamic data.

• Journal of the Korean Chemical Society
• /
• v.37 no.4
• /
• pp.442-447
• /
• 1993

The thermodynamic parameters (${\Delta}$G, ${\Delta}$H and ${\Delta}$S) of lanthanides(III)-benzoylformate complexes in aqueous solution have been determined in the ionic medium of 0.1M $NaClO_4$ at 25$^{\circ}C$, using pH and enthalpy titration method. The stability constants of the lanthanide(III)-benzoylformate complexes (1 : 1) agree well with the general relationships for the bidentate ligands (e.g., log${\beta}_1$ vs. p$K_a$). Thermodynamic evidences show that the oxygen atom in ketone group is coordinated along with the carboxylate group. It is ascribed to the increasing charge density on the oxygen atom in ketone group due to the conjugation effect in the benzoylformate ligand. Thermodynamic results also indicate that the complexes are stabilized by the enthalpy effect caused by the ionic interaction of metal-oxygen bond as well as the entropy effect.

• Journal of the Korean Chemical Society
• /
• v.35 no.1
• /
• pp.64-69
• /
• 1991

Kinetics of the reaction of p-methylphenacyl arenesulfonates with pyridine in acetonitrile were investigated by an electric conductivity method at 1∼2000 bars and 35∼55$^{\circ}C$. The rates of these reactions were increased with raising pressures and temperatures. The activation enthalpy(${\Delta}H^{\neq}$), entropy(${\Delta}S^{\neq}$) and activation volume(${\Delta}V^{\neq}$) of the reaction were obtained with the rate constants. Activation volume and entropy were both negative valued, and activation enthalpy was positive. The acteivation parameters (${\Delta}V^{\neq}$ and ${\Delta}S^{\neq}$) were decreased with increasing pressure. From all of the above results, it was found that this reaction proceeds on the S$_N$2 in which C${\cdots}$O bond breaking is more advanced as pressure increases.

• Journal of the Korean Chemical Society
• /
• v.19 no.3
• /
• pp.156-162
• /
• 1975

Rates of reactions of methanesulfonyl chloride with various substituted anilines have been measured in methanol. Substituent effects in aniline are found to be linearly correlated with pKa(Bronsted relation with ${\beta}$ = 0.84) and ${\rho}$(Hammett equation with ${\rho}$ = -2.46) respectively. The results are interpreted in terms of degree of bond-formation at the transition state, which was found to have progressed relatively further. The rates for o-methylaniline deviated from the Bronsted plot established by meta and para substituted anilines because of a steric effect of ortho position in aniline. Activation parameters, ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ have also been determined. The enthalpy of activation showed a regular variation in that electron donating substituents in the p-substituted aniline decrease ${\Delta}H^{\neq}$ and increase the negative value of ${\Delta}S^{\neq}$.

• Journal of the Korean Chemical Society
• /
• v.60 no.1
• /
• pp.9-15
• /
• 2016

The theoretical investigation has been performed to predict detonation velocity, detonation pressure, and thermodynamic stability of HMX/LLM-116 cocrystal. All possible geometries of HMX, LLM-116, and cocrystal have been optimized at the B3LYP/cc-pVTZ level of theory. The binding energy for the trigger bond and cluster has been calculated to predict the thermodynamic stability. The MP2 binding energies were obtained using single point energy calculation at the B3LYP optimized geometries, and the density has been calculated from monte carlo integration. The detonation velocity and detonation pressure have been calculated using Kamlet-Jacobs equation, while enthalpy has been predicted at the CBS-Q level of theory.