• Bulletin of the Korean Chemical Society
• /
• v.29 no.1
• /
• pp.191-196
• /
• 2008

Kinetic studies of the reactions of a-bromoacetanilides [YC6H4NHC(=O)CH2Br] with substituted benzylamines (XC6H4CH2NH2) have been carried out in dimethyl sulfoxide at 35.0 oC. The Hammett plots for substituent (Y) variations in the substrate (log kN vs. sY) are biphasic concave upwards/downwards with breaks at Y = 4-Cl (sY = 0.23). The Hammett coefficients rY and the cross-interaction constant rXY (= +0.16) are positive for sY 0.23, while the rY values are positive/negative [rY > 0 for X = (4-MeO and 4-Me) and rY < 0 for X = (H, 4-Cl and 3-Cl)] and the rXY (= -1.51) value is negative for sY ³ 0.23. Based on these and other results, the benzylaminolyses of a-bromoacetanilides are proposed to proceed through rate-limiting expulsion of the bromide leaving group from a zwitterionic tetrahedral intermediate, T, with a bridged transition state for s Y 0.23, while the reaction proceeds through concerted mechanism with an enolate-like TS in which the nucleophile attacks the a-carbon for s Y ³ 0.23.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.2
• /
• pp.205-208
• /
• 2003

Laser-induced Raman spectroscopy has been utilized to demonstrate its feasibility for studying the kinetics of imine formation in chloroform solvent. The imine formation, by the nucleophilic addition of primary amine to the carbonyl group of ketone, has been monitored at ten minute intervals for eight hours. The intensity of the C=O stretching mode at 1684 $cm^{-1}$ was measured to determine the rate constant of the reaction. In order to correct the sample-to-sample fluctuations in Raman peak area, this peak was normalized to the C-Cl bending peak at 666 $cm^{-1}$. By the peak area change during the course of reaction, the second order rates at three different temperatures have been determined. The substituent effects on the π conjugations of imine product have also been investigated. On the basis of Raman frequency shifts, the delocalization properties of the aromatic system modified by substitution of a hydrogen atom with -Cl and $-CH_3O$ groups could be clearly understood.

• Journal of the Korean Applied Science and Technology
• /
• v.12 no.2
• /
• pp.93-98
• /
• 1995

The rate constant of Nucleophilic addition of sodium thiophenoxide to nitrone were determined by UV Spectrophotometry and a rate equation which can be applied over wide pH range was obtained. Base on the rate equation, general base effect, substituent effect and final product, plausible mechanism of addition reaction have been proposed. Blow pH 3.0, the reaction was initiated of thiophenol, and in the range of pH $3.0{\sim}10.0$, proceeded by the competitive addition of thiophenol and thiophenoxide anion. Above the pH 10.0, the reaction proceeded through the addition of a thiophenoxide anion.

• Journal of the Korean Applied Science and Technology
• /
• v.12 no.2
• /
• pp.85-92
• /
• 1995

The rate constant of the nucleophilic addition of 1-propanethiol to ${\alpha}-phenyl-N-iso-propylnitrone$ derivatives were determined at various pH and a rate equation which can be applied over wide pH range is obtained. Final product of the addition reaction was ${\alpha}-thiopropyl-p-phenylbenzylideneamine$. Base on the rate equation, general base effect, substituent effect and final product, plausible mechanism of addition reaction have been proposed. Below pH 3.0, the reaction was initiated by the addition of 1-propanthiol, and in the range of pH 3.0-10.0, proceeded by the competitive addition of 1-propanethiol and propanethiolate. Above the pH 10.0, the reaction proceeded through the addition of propanethiolate.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.4
• /
• pp.851-855
• /
• 2008

The reactions of O,O-diphenyl Z-S-phenyl phosphorothiolates with X-pyridines have been studied kinetically in acetonitrile at $35.0{^{\circ}C}$. The Hammett plots for substituent (Z) variations in the leaving group (log $k_2$ vs. $\sigma$ Z) are biphasic concave downwards with breaks at Z = H. The large magnitudes of ${\rho}X(\rho_{nuc})$, ${\beta}X(\rho_{nuc})$, and the cross-interaction constant, $\rho$XZ, suggest frontside nucleophilic attack toward the leaving group. The sign reversal of $\rho$Z from positive in $\sigma$ Z $\leq$ 0 to negative in $\sigma$ Z $\geq$ 0 is interpreted as the change in mechanism from concerted to stepwise with rate-limiting expulsion of the leaving group. The anomalous negative sign of $\rho$ Z for leaving groups with electron-withdrawing substituents is interpreted as the intramolecular ligand exchange process of the leaving group from the equatorial position in the intermediate to the apical position in the TS.

• The Korean Journal of Pesticide Science
• /
• v.3 no.2
• /
• pp.86-89
• /
• 1999

A series of methanesulfonamide (I a- I g) and phenylhydrazone (IIa-IIh) derivatives were synthesized and their fungicidal activity in vitro against gray mold (BC: Botrytis cinerea), phytophthora blight (PC: Phytophthora capsici) and sheath blight (RS: Rhizoctonia solani) were measured by agar dilution method. The (II) deriviatives showed higher activity than ( I ) derivitives. And the relative orders of the fungicidal activity are BC=PC>RS, Among these compounds, 3-chlorophenyl substituent, IIg showed the most highest activity ($pI_{50}=3.96$) against PC. From the parameter focusing technique, major factors on the activity were ovality, polar and logP constant and so on.

• Journal of the Korean Applied Science and Technology
• /
• v.10 no.2
• /
• pp.65-72
• /
• 1993

The kinetics of the addition of thiourea to cinnamenylisophorone derivatives(X : H, p-Br, $p-CH_3$ $m-CH_3$, $p-OCH_3$) was investigated using ultraviolet spectrophotometry in 20%(v/v) dioxane-$H_2O$ at $25^{\circ}C$. A rate equation which can be applied over wide pH range(pH $1.0{\sim}13.0$) was obtained. In order to investigate the substituent effects of cinnamenylisophorone derivatives. Hammett constant was plotted. As the result, the rate of uncleophilic addition of thiourea to cinnamenylisophorone derivatives was facilitated by electron donating group. It was found that addition of neutral thiourea which was not dissociated at the pH $1.0{\sim}9.0$ was proceeded, the reaction was proceeded by addition of dissociated anion of thiourea above the pH 10.0. On the basis of this kinetic study, the reaction mechanism of nucleophilic addition of thiourea was investigated.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.10
• /
• pp.3587-3591
• /
• 2011

The reactions of O,O-diethyl Z-S-aryl phosphorothioates with X-benzylamines are kinetically investigated in dimethyl sulfoxide at $85.0^{\circ}C$. The Hammett (log $k_2$ vs ${\sigma}x$) and Br$\ddot{o}$nsted [log $k_2$ vs $pK_a$(X)] plots are biphasic concave downwards for substituent X variations in the nucleophiles with a break point at X = H. The signs of the cross-interaction constants (${\rho}xz$) are positive for both the strongly and weakly basic nucleophiles. Considerably great magnitude of ${\rho}xz$ (= 6.56) value is observed with the weakly basic nucleophiles, while ${\rho}xz$ = 0.91 with the strongly basic nucleophiles. Proposed reaction mechanism is a stepwise process with a rate-limiting leaving group expulsion from the intermediate involving a backside nucleophilic attack with the strongly basic nucleophiles and a frontside attack with the weakly basic nucleophiles. The kinetic results are compared with those of the benzylaminolysis of O,O-diphenyl Z-S-aryl phosphorothioates.

• Bulletin of the Korean Chemical Society
• /
• v.8 no.3
• /
• pp.168-170
• /
• 1987

The reaction between 1-benzyl-3-carbamoyl-1,4-dihydropyridine (BNAH) 1 and various 1-arylpyridinium salts 2, and the reaction between 1-(4-methylphenyl)-1,4-dihydropyridine 4b and 1-aryl-3-carbamoylpyridinium (1-arylnicotinamide) salts 5 were carried out. The extents of reaction in equilibrium were estimated by nmr integration data. The equilibrium constants for the reactions, K, and the standard Gibbs free energy changes for the reduction of the pyridinium salts to the corresponding 1,4-dihydropyridines ${\Delta}G^{\circ}'$ were evaluated. The Hammett plot of log K for the reaction between 1 and 2, and ${\Delta}G^{\circ}'$ against ${\sigma}_p$ of the substituents in 1-aryl moiety shows linear correlation with the reaction constant ${\rho}$ of 9.4 (for log K vs ${\sigma}_p$) and -54.5 KJ/mole (for ${\Delta}G^{\circ}'$ vs ${\sigma}_p$). It was found that 1-aryl-1,4-dihydropyridines have much higher reducing power than the corresponding 1-aryl-1,4-dihydronicotinamides, and the power is affected greatly by the electron-withdrawing ability of the substituents in aryl group. The reactions were utilized for preparation of 1,4-dihydropyridines bearing highly electron-withdrawing groups such as 4-nitrophenyl and 2,4-dinitrophenyl, which could not be obtained by conventional dithionite reduction of the corresponding pyridinium salts due to the base-labile nature of the salts.

• The Korean Journal of Pesticide Science
• /
• v.3 no.1
• /
• pp.29-36
• /
• 1999

A series of N-phenyl-O-phenylthionocarbamate derivatives were synthesized and determinated fungicidal activities in vitro against gray mold (Botrytis cinerea) and capsicum phytophthora blight (Phytophthora capsici) which showed resistance and sensitivity to benomyl and metalaxyl as systemic fungicides, respectively. The structure-activity relationship (SAR) was investigated by Free-Wilson analysis method and Hansch method. From the basis on the findings, the N-phenyl(X) groups had more contributions than O-phenyl(Y) groups did and ortho-substituents on the N-phenyl group showed high fungicidal activities. Especially, 4-cyano substituent, 2 as X-group showed 50% inhibition($pI_{50}=5.50$) of hyphae growth at 0.8ppm against resistance P. capsici (RPC) And hydroxyl substituents, 12 and 23 displayed the highest fungicidal activity against resistant B. cinerea (RBC), sensitive B. cinerea (SBC), and sensitive P. capsici (SPC). Antifungal activities of SPC were dependent upon molar refractivity (MR) constant and those of others relied on hydrophobic parameters (${\sigma}$ and logP). For increasing fungicidal activity against RPC and SBC, the optimum values of the sigma (${\sigma}$) and field(F) constants as electron withdrawing groups were 0.32 and 0.18, respectively.