• Bulletin of the Korean Chemical Society
• /
• v.28 no.11
• /
• pp.1993-1995
• /
• 2007

A substitution effect on the electronic transition of bi-substituted benzyl-type radicals was discovered. The origin of the electronic D1 → D0 transition of benzyl-type radicals was red-shifted upon substitution to the benzene ring. For symmetric bi-substituted benzyl-type radicals, it was found that the predicted shift obtained from mono-substituted benzyl-type radicals agreed well with the observation. The reason for this agreement is believed that the substituent contributes independently to the electronic energy. The substitution effect was applied to the symmetric bi-substituted difluoro-, dichloro- and dimethylbenzyl radicals.

• Journal of the Korean Ceramic Society
• /
• v.34 no.12
• /
• pp.1261-1267
• /
• 1997

Four kids of powder admixtures(A, B, C, D) based on anhydrite were manufactured by mixing at a fixed rate of II-anhydrite, fly ash and active silica as an industrial by-product. Fluidity properties of cement paste such as mini-slump, apparent viscosity with elapsed time, as well as setting time of cement pastes of these admixtures substituted up to 11wt% of cement were compared to those of cement paste(SS) substisuted by marketed high-strength powder admixture(S). Among these powder admixtures, the fluidity of cement pastes(PA, PC) substituted by A and C powder admixtures manufactured from II-anhydrite and fly ash had an excellent property than that of cement paste substituted by marketed powder admixture and also a good fluidity-retention effect with elapsed time by adding of superplasticizer. The setting time of cement paste substituted by powder admixtures based on anhydrite slightly retarded than that of cement paste substituted by marketed powder admixture.

• Journal of the Korean Chemical Society
• /
• v.11 no.4
• /
• pp.170-172
• /
• 1967

2-Phenyl-5-substituted phenyltetrazole and 2-substituted phenyl-5-phenyltetrazole were prepared from the corresponding hydrazone and phenyl azide with 2-methoxyethanol and metallic sodium as reaction medium at 110~115 $^{\circ}C$. At this reaction condition, however, the preparation of 2-substituted phenyl-5-phenyltetrazoles with substituents of relatively high Hammett substituent constant was unsuccessful. Surprisingly it was found that the solvent molecule was exchanged with substituent during the reaction when tried to obtain 2-m-fluorophenyl-5-phenyltetrazole using benzaldehyde m-fluorophenylhydrazone as starting material. Also disscussed the effect of electronic nature of substituents on the formation of 2,5-diphenyltetrazole derivatives.

• Bulletin of the Korean Chemical Society
• /
• v.9 no.3
• /
• pp.164-166
• /
• 1988

7-Dithiocarboxy-3-phenyl-5,6-dihydro imidazo[2,1-b]thiazolium-betaine (2) was prepared by treatment of 3-phenyl-5,6-dihydro imidazo[2,1-b]thiazole (1) with carbon disulfide in acetone at room temperature. On the reaction of 2 with para-substituted phenacyl bromides (4) having the electron withdrawing property by virtue of (+) resonance (R) < (-) inductive (I) or (-) resonance (R), (-) inductive (I) effect, ring transformation product p-substituted-2-[2-[7-(p-substituted benzoyl)-5-thioxo-2,3-dihydro-1H-imidazo[1,2-c] thiazol-1-yl]-2-phenylvinylthio] acetophenone (6) was obtained; however, when R is electron donating grops with (+) resonance (R) > (-) inductive (I) effect the quarternary ammonium salt 7-(p-substituted phenyl) carbonyl methyl-3-phenyl-5,6-dihydro imidazo [2,1-b] thiazolium bromide (8) is formed. The reaction of 2 with unsubstituted-phenacyl bromide (R = H), on the other hand, gives 6a and 8a to the similar ratio, respectively.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.10
• /
• pp.2877-2882
• /
• 2013

Second-order rate constants ($k_{Ox^-}$) have been measured spectrophotometrically for nucleophilic substitution reactions of 4-nitrophenyl X-substituted-cinnamates (7a-7e) and Y-substituted-phenyl cinnamates (8a-8e) with butane-2,3-dione monoximate ($Ox^-$) in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The Hammett plot for the reactions of 7a-7e consists of two intersecting straight lines while the Yukawa-Tsuno plot exhibits an excellent linearity with ${\rho}_X$=0.85 and r=0.58, indicating that the nonlinear Hammett plot is not due to a change in the rate-determining step but is caused by resonance stabilization of the ground state (GS) of the substrate possessing an electron-donating group (EDG). The Br${\o}$nsted-type plot for the reactions of Y-substituted-phenyl cinnamates (8a-8e) is linear with ${\beta}_{lg}$ = -0.64, which is typical of reactions reported previously to proceed through a concerted mechanism. The ${\alpha}$-nucleophile ($Ox^-$) is more reactive than the reference normal-nucleophile ($4-ClPhO^-$). The magnitude of the ${\alpha}$-effect (i.e., the $k_{Ox^-}/k_{4-ClPhO^-}$ ratio) is independent of the electronic nature of the substituent X in the nonleaving group but increases linearly as the substituent Y in the leaving group becomes a weaker electron-withdrawing group (EWG). It has been concluded that the difference in solvation energy between $Ox^-$ and $4-ClPhO^-$ (i.e., GS effect) is not solely responsible for the ${\alpha}$-effect but stabilization of transition state (TS) through a cyclic TS structure contributes also to the Y-dependent ${\alpha}$-effect trend (i.e., TS effect).

• Bulletin of the Korean Chemical Society
• /
• v.30 no.12
• /
• pp.2913-2917
• /
• 2009

Second-order rate constants (k$_{Nu–}$) have been measured for nucleophilic substitution reactions of Y-substituted phenyl benzoates (1a-i) with butane-2,3-dione monoximate ($Ox^-\;an\;\alpha$-nucleophile) and Z-substituted phenoxides in 80 mol% H$_2$O/20 mol% DMSO at 25.0${\pm}$0.1$^{\circ}C$. Hammett plots correlated with ${\sigma}^o$ and ${\sigma}^-$ constants for reactions of 1a-h with Ox$^–$ exhibit many scattered points. In contrast, the Yukawa-Tsuno plot results in a good linear correlation with ${\rho}_Y$ = 2.20 and r = 0.45, indicating that expulsion of the leaving group occurs in the rate-determining step (RDS). A stepwise mechanism with expulsion of the leaving-group being the RDS has been excluded, since Y-substituted phenoxides are less basic and better nucleofuges than Ox$^–$. Thus, the reactions have been concluded to proceed through a concerted mechanism. Ox$^–$ is over 10$^2$ times more reactive than its reference nucleophile, 4-chlorophenoxide (4-ClPhO$^–$). One might suggest that stabilization of the transition-state (TS) through intramolecular general acid/base catalysis is responsible for the ${\alpha}$-effect since such general acid/base catalysis is not possible for the corresponding reactions with 4-ClPhO$^–$. However, destabilization of the ground-state (GS) of Ox$^–$ has been concluded to be mainly responsible for the ${\alpha}$-effect found in this study on the basis of the fact that the magnitude of the ${\alpha}$-effect is independent of the nature of the substituent Y.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.11
• /
• pp.3607-3617
• /
• 2012

In this paper, the study of various ortho- and meta-substituted Magnolol derivatives is presented. The reaction enthalpies related to three antioxidant action mechanisms HAT, SET-PT and SPLET for substituted Magnolols have been calculated using DFT/B3LYP method in gas-phase and water. Calculated results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP) and oxidation/reduction enthalpy (O/RE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In ortho- position, substituents show larger effect on reaction enthalpies than in meta-position. In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. In gas-phase, BDEs are lower than PAs and IPs, i.e. HAT represents the thermodynamically preferred pathway. On the other hand, SPLET mechanism represents the thermodynamically favored process in water. Results show that calculated enthalpies can be successfully correlated with Hammett constants (${\sigma}_m$) of the substituted Magnolols. Furthermore, calculated IP and PA values for substituted Magnolols show linear dependence on the energy of the highest occupied molecular orbital ($E_{HOMO}$).

• Journal of the Korean Chemical Society
• /
• v.8 no.4
• /
• pp.153-157
• /
• 1964

The syntheses of substituted tert.-butyl ${\beta}$-(o-tolyl)- perpropionates via intermediates obtained by chloromethylation, malonic syntheses and decarboxylation is described. The intermediates substituted with a group possessing moderate substituent effect such as bromo, chloro, and methyl group were obtained in good yields. The nitro-substituted intermediat was obtained in poor yield. The chloromethylation of toluenes containing electron donating groups resulted in polymerization.

• Archives of Pharmacal Research
• /
• v.12 no.3
• /
• pp.149-153
• /
• 1989

Seven 2, 3-diphenyl-5-methoxyindole derivatives were synthesized. The effect of structural variation of these molecules on biological activities was examined. None of the tested compounds was found to be toxic up 5 gm/Kg body weight. Four compounds demonstrated smooth muscle relaxant effects and one showed a persistent hypotensive effect. Only the parent compound, 2, 3-diphenyl-5-methoxyindole, showed a significant analgesic effect.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.7
• /
• pp.604-609
• /
• 1995

The relative dissociation constants of 4-substituted bicyclo[2,2,2]octane-1-carboxylic acids, 4-substituted quinuclidines, and 3-and 4-substituted pyridines were collected from a number of sources. In order to understand the actual substituent effects with a combination of inductive effect (σI) and resonance effect (σR) components. The DSP correlation has been employed statistically for each of the p-and m-series. The inductive effect from the m-position was 1.2 times more effective than that from the p-position and the requirement of σR+ for the best-fit led to the conclusion that pyridine system belongs to the σ+-class reactivity. Also compared with results from Yukawa-Tsuno's LArSR treatment and relevant treatment.