• Journal of the Korean Chemical Society
• /
• v.51 no.3
• /
• pp.258-264
• /
• 2007

Novel fluoride sensory systems have been successfully developed. Previously developed method of the fluoride-induced lactonization to fluorescent molecules was detailed, and newly developed fluoride-induced aromatic cyclization scheme was introduced. Based on the strategies using the specific affinity of fluoride to silicon, our systems are highly selective for fluoride ion. Incorporation of the developed sensor to a conjugated polymer has successfully enhanced its sensitivity to fluoride ion.

• Journal of the Korean Chemical Society
• /
• v.41 no.1
• /
• pp.22-46
• /
• 1997

Kinetic studies on nucleophilic substitution reaction of phenacyl bromide and phenacyl chloride with pyridines were conducted at 25℃ and 35℃ in methanol-acetonitrile solvents mixtures. It was shown that the reaction proceeds via an SN2 reaction mechanism based on the transition state parameters, ΔH≠ and ΔS≠ and Bro nsted β values. Quantum mechanical model predicted a product-like transition state, where bond-formation is much more progressed than bond breaking, upon changing the leaving group to that with a better leaving ability.

• Journal of the Korean Chemical Society
• /
• v.33 no.4
• /
• pp.413-418
• /
• 1989

The rates for the reaction of substituted 2-phenylethyl tosylates with substituted pyridines were measured in acetonitrile and that of 2-PNS with substituted pyridines were investigated in both acetonitrile and methanol. The substitutent effect was accelerated by an electron-donating substituent on both substrate and nucleophile. Results showed that More O'Ferrall and quantum mechanical model of predicting transition state structure suggest the reaction proceeds via an $S_N2$ mechanism, in which bond-breaking is more advanced than bond-formation. Transition state variation predicted with the quantum mechanical model is consistent with the experimental results, whereas the predictions provided by the More O'Ferrall plots is found to be inconsistent in leaving group. In the reaction of 2-PNS, the rate constants in acetonitrile were larger than that in methanol.

• Journal of the Korean Chemical Society
• /
• v.34 no.3
• /
• pp.221-226
• /
• 1990

The solvolysis of substitued phenacyl tosylates was studied in binary solvent mixtures of methanol-acetonitrile and methanol-acetone at 55$^{\circ}C$. Except for m-nitrophenacyl tosylate, the rate constants were increased with both of electron-donating substituents and electron-withdrawing ones and its rate constants were the largest in the binary solvent mixtures of 90% MeOH-10% MeCN. The results show that the reactions were changed with dissociative $S_N2$ mechanism judging from the magnitude of 1/m values going from the electron-withdrawing group to the electron-donating one of the substrate. And above results were consisted with the account for the PES model and QM approach.

• Journal of the Korean Chemical Society
• /
• v.31 no.4
• /
• pp.364-368
• /
• 1987

The addition reactions of thioglycolic acid, benzenethiol and benzylmercaptan to ${\beta}-acetyl-{\beta}-benzoylstyrene$ were investigated. ${\beta}-Acetyl-{\beta}-benzoylstyrene$ derivatives easily underwent addition reactions with thioglycolic acid, benzenethiol, and benzylmercaptan to form five(2-acetyl-2-benzoyl-1-phenylethyl) thioglycolic acid derivatives (IIa-IIe), five (2-acetyl-2-benzoyl-1-phenylethyl)benzenethiol (IIIa-IIIe) derivatives and five (2-acetyl-2-benzoyl-1-phenylethyl)benzylmercaptan derivatives (IVa-IVe), respectively.

• The Korean Journal of Pesticide Science
• /
• v.5 no.2
• /
• pp.13-17
• /
• 2001

A synthesis of new 2-phenylimino-1,3-thiazolines 2 for the purpose of development of new agrochemical fuugicide was described. Reaction of chlorine with diketene followed by treatment of benzylamine without isolation of intermediate 8a gave ${\gamma}-chloro-{\beta}-keto$ benzylamide 10a. Thioureas 4 obtained from the reaction of methyl isothiocyanate with aniline derivatives were subjected to 10a in acetone solution to afford the corresponding 2-phenylimino-1,3-thiazoline hydrochloric acid salts 2 through unisolable inltermediates 11 and 12. The plausible reaction mechanism including nucleophilic attack of sulfur assisted neighboring nitrogen lone pair electron on phenyl of thiourea 4 was discussed.

• Journal of the Korean Chemical Society
• /
• v.40 no.10
• /
• pp.663-669
• /
• 1996

The rate constants for the nucleophilic addition reactions of thioglycolic acid to vinylsulfilimine(VSI) derivatives(p-OCH3, H, p-Cl and p-Br) were determined by an ultraviolet spectrophotometric method, and rate equations which can be applied over a wide pH range were obtained. On the basis of rate equation, general base catalysis and substituent effect, a plausible addition reaction mechanism was proposed: Below pH 3.0, the reaction was proceeded via the addition of neutral molecule to carbon-carbon double bond after protonation at the nitrogen atom of the sulfilimine, and in the pH range of 3.0 to 9.0, the neutral molecule and its anion attacked to carbon-carbon double bond competitively. Above pH 9.0, sulfide anion added to the double bond (Michael type addition).

• Journal of the Korean Chemical Society
• /
• v.35 no.3
• /
• pp.268-274
• /
• 1991

The rate constants for the nucleophilic addition reactions of thiourea to ${\beta}$-nitrostyrene derivatives(p-H, p-Cl, p-CH$_3$, p-OCH$_3$, p-NO$_2$) were determined by UV spectrophotometer and rate equations which can be applied over a wide pH ranges were obtained. On the basis of substituent effect, general base catalysis and rate equations, a reaction mechanism was proposed and revealed quantitively. Above pH 9.00, sulfide anion adds to the double bond(Michael type addition) and between pH 7.00 and 9.00, the neutral molecules and its anions add to the double bond competitively. Below pH 7.00, the addition reaction to double bond is initiated by the addition of neutral thiourea molecule.

• Journal of the Korean Chemical Society
• /
• v.32 no.3
• /
• pp.260-266
• /
• 1988

The rate constants for the nucleophilic addition reactions of thioglycolic acid and cysteine to ${\beta},\;{\beta}$-dichlorostyrene derivatives(p-H, p-Cl, $p-CH_3,\;and\;p-OCH_3$) were photochemically determined at various pH and a rate equation which can be applied over a wide pH range was obtained. On the bases of rate equation, general base catalysis and substituent effect, the plausible addition reaction mechanism was proposed: Above pH 9.0, the reaction was initiated by the addition of sulfide anion, and in the range of pH 7.0 to 9.0, the neutral molecules and it's anions attacked to the double bond, competitively. However, below pH 7.0, only the neutral molecules of thioglycolic acid or cysteine added to the carbon-carbon double bond.

• Journal of the Korean Chemical Society
• /
• v.28 no.6
• /
• pp.366-373
• /
• 1984

Methanolysis rates of benzylbenzenesulfonates, substituted both on the substrate (Y) and on the leaving group (Z), were determined in MeOH-MeCN mixtures. The results showed that the reaction proceeds via the dissociative $S_N2$ mechanism, in which bond breaking proceeds in greater degree compared to bond formation at the transition state(TS). Multiple Hammett correlation analysis showed that the cross term, ${\rho}_{YZ}$, is very small and hence the cross interaction of two substituents, Y and Z, at the TS is not important, supporting the dissociative $S_N2 $ type mechanism. While transition state variations predicted by the quantum mechanical model is shown to agree in general with the experimental results, those predicted by the potential energy surface model failed to account for the leaving group effect properly.