• Journal of the Korean Chemical Society
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• v.19 no.3
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• pp.156-162
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• 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
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• v.28 no.4
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• pp.210-216
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• 1984

Solvatochromic comparison methods were applied to determine Taft's solvent parameters, ${\pi}^{\ast}$(solvent polarity-polarizability), ${\alpha}$(solvent hydrogen bond donor acidity) and ${\beta}$ (solvent hydrogen bond acceptor basicity) for MeOH-MeCN solvent mixtures. Swain's solvent parameters A(anion solvation scale) and B(cation solvation scale) were also determined by least square fitting of kinetic data in the same binary solvent mixtures. It was found that: (i)${\beta}$ depends on the basicity of the solvent and increases with the MeOH content owing to the increase in polymeric structure of methanol; (ii) ${\pi}^{\ast}$depends on the dipole moment of the solvent and increases with the MeCN content of the solvent; (iii) ${\alpha}$ increases rapidly with the MeOH content as the hydrogen bond donor acidity of the solvent mixtures increases. Taft's reaction constants a and s and Swain's reaction constants a and b were determined for the reactions reported from our laboratory previously using solvent parameters determined in this work. No meaningful inter-relationship was found between the two set of reaction parameters, but a good linear correlation was found between the ratios a/s and a/b. Solvent effect on the reaction mechanism, substituent effect and leaving group ability were examined in the light of these reaction constants ratios.

• Applied Biological Chemistry
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• v.38 no.5
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• pp.455-462
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• 1995

The new six herbicidal N-[(pyrimidin-2-yl)aminocarbonyl]-2-substituted-6-(1-hydroxy-2-fluoroethyl)benzenesulfonamide derivatives(S) were synthesized and rate constants for the hydrolysis of thier in the range of pH $1.0{\sim}10.0$ have been studied in 15%(v/v) aqueous acetonitrile solution at $45^{\circ}C$. From the basis of the results, pH-effect, solvent effect, ortho-substituent effect, thermodynamic parameters(${\Delta}H^{\neq}$ & ${\Delta}S^{\neq}$), pKa constant(4.80), rate equation, analysis of hydrolysis products(2-(1-hydroxy-2-fluoroethyl)benzenesulfonamide & 4,6-dimethoxyaminopyrimidine), it may be concluded that the general acid catalyzed hydrolysis through $A-S_E2$ mechanism and specific acid catalyzed hydrolysis through A-2 type(or $A_{AC}2$) mechanism proceeds via conjugate acid($SH^+$) and tetrahedral intermediate(I) below pH 8.0, whereas, above pH 9.0, the general base catalyzed hydrolysis by water molecules(B) through $(E_1)_{anion}$ mechanism proceeds via conjugate base(CB). In the range between $pH\;7.0{\sim}pH\;9.0$, these two reactions occur competitively.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1625-1629
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• 2011

Kinetic studies of the reactions of O,O-diphenyl Z-S-aryl phosphorothioates with X-benzylamines have been carried out in dimethyl sulfoxide at 55.0 $^{\circ}C$. The Hammett (log $k_2$ vs ${\sigma}_X$) and Bronsted [log $k_2$ vs $pK_a(X)$] plots for substituent X variations in the nucleophiles are biphasic concave downwards with a maximum point at X = H, and the unusual positive ${\rho}_X$ and negative ${\beta}_X$ values are obtained for the strongly basic benzylamines. The sign of the cross-interaction constant (${\rho}_{XZ}$) is negative for both the strongly and weakly basic nucleophiles. Greater magnitude of ${\rho}_{XZ}$ value is observed with the weakly basic nucleophiles (${\rho}_{XZ}$ = -2.35) compared to with the strongly basic nucleophiles (${\rho}_{XZ}$ = -0.03). The deuterium kinetic isotope effects ($k_H/k_D$) involving deuterated benzylamines [$XC_6H_4CH_2ND_2$] are primary normal ($k_H/k_D$ > 1). The proposed mechanism is a concerted $S_N2$ involving a frontside nucleophilic attack with a hydrogen bonded, four-center-type transition state for both the strongly and weakly basic nucleophiles. The unusual positive ${\rho}_X$ and negative ${\beta}_X$ values with the strongly basic benzylamines are rationalized by through-space interaction between the ${\pi}$-clouds of the electron-rich phenyl ring of benzylamine and the phenyl ring of the leaving group thiophenoxide.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4185-4190
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• 2011

The nucleophilic substitution reactions of ethylene phosphorochloridate (1c) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $5.0^{\circ}C$. The anilinolysis rate of 1c involving a cyclic five-membered ring is four thousand times faster than its acyclic counterpart (1a: diethyl chlorophosphate) because of great positive value of the entropy of activation of 1c (${\Delta}S^{\neq}=+30\;cal\;mol^{-1}K^{-1}$ compared to negative value of 1a (${\Delta}S^{\neq}=-45\;cal\;mol^{-1}K^{-1}$) over considerably unfavorable enthalpy of activation of 1c (${\Delta}H^{\neq}=27.7\;kcal\;mol^{-1}$) compared to 1a (${\Delta}H^{\neq}=8.3\;kcal\;mol^{-1}$). Great enthalpy and positive entropy of activation are ascribed to sterically congested transition state (TS) and solvent structure breaking in the TS. The free energy correlations exhibit biphasic concave upwards for substituent X variations in the X-anilines with a break point at X = 3-Me. The deuterium kinetic isotope effects are secondary inverse ($k_H/k_D$ < 1) with the strongly basic anilines and primary normal ($k_H/k_D$ > 1) with the weakly basic anilines and rationalized by the TS variation from a dominant backside attack to a dominant frontside attack, respectively. A concerted $S_N2$ mechanism is proposed and the primary normal deuterium kinetic isotope effects are substantiated by a hydrogen bonded, four-center-type TS.

• Archives of Pharmacal Research
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• v.22 no.6
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• pp.592-607
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• 1999

2-(1-Aryl-1-hydroxymethyl)-and 2-aroyl-DHAQ derivatives (DHAQ, 1,4-dihydroxy-,10-anthraquinone), and 2-(1-aryl-1-hydroxymethyl)-ATO derivatives (ATO, anthraceneactivity (T/C 125~128%), though their cytotoxicity was not further improved compared to that of 2-(1-aryl-1-dydroxymethyl)-1,4-dihydroxy-9,10-anthraquinones. They manifested no correlation between the cytotoxicity and the antitumor activity. In case of 2-[1-hydroxy-1-(4-propylphenyl)-methyl]-ATO, the most bioactive one in viv-1,4,9,10-tetraone) were synthesized and their antitumor activities were determined. 2-(1-Aryl-1-hydroxymethyl)-DHAQ derivatives showed a stronger cytotoxicity compared to the series of 2-(1-hydroxyalkyl)-1,4-dihydroxy-9,10-anthraquinone derivatives. It was suggested that the presence of aryl group at the side chain accelerated the bioreductive activation leading to cell death. 2-Aroyl-DHAQ derivatives, despite their higher electrophilicity, revealed smaller cytotoxicity and antitumor activity (expressed by T/C value) than 2-(1-aryl-1-hydroxymethyl)-DHAQ derivatives. Thus, no consistent relationship between the electronic effect on aromatic side chain and the cytotoxicity was observed. ATO series exhibited a higher antitumor o among the same series, it showed an $ED_{50}$ value of 10.2 mg/mL and a T/C value of 218%. It is assumed that the anthrancene1,4,9,10-tetraones after uptake into cellular tissues might be transformed to a cytotoxic metabolite(s).

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.243-247
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• 1979

Kinetics of the reaction of phenethyltosylate with substituted pyridines at 50, 60 and 70$^{\circ}C$ in acetonitrile were investigated by an electric conductivity method. The effects of substituents on the reaction of phenethyltosylate with pyridines were discussed. The rates of reaction were increased with electron donating power of substituents of pyridines. The isokinetic relationship was shown $E_{\alpha}$ and ${\Delta}S^{\neq}$, it's temperature was 240$^{\circ}$K. Bronsted plots were excellent linear except for 4-amino pyridine given by the following equation, logk=O. 22pKa-3.71 (r=O. 986). According to a plot of log k against Hammett substituent constants, the Iinearity was good except for bamino pyridine too, log k= -1.330${\sigma}$+0.08 (r= -0.987). In both cases, deviation of 4-amino pyridine from linearity was considered to solvent effect, resonance effect and ${\sigma}$ value itself. From all the above results, this reaction was found typical $S_N2$ reaction which the rates of reaction was determined by C…N bond formation at transition state.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1153-1157
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• 2011

A kinetic study is reported for aminolysis of S-4-nitrophenyl X-substituted thiobenzoates 3a-g in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. Thiol esters 3a-g are 7.8-47.6 fold more reactive than the corresponding oxygen esters (i.e., 4-nitrophenyl X-substituted benzoates 1a-g). Such reactivity order appears to be in accordance with the expectation that 4-nitrothiophenoxide in 3a-g is a better nucleofuge than 4-nitrophenoxide in 1a-g since the former is 2.64 pKa units less basic than the latter. Hammett plot for the reactions of 3a-g exhibit poor correlation coefficients ($R^2$ = 0.977-0.986) with negative deviation by substrates possessing an electrondonating group (EDG), while the Yukawa-Tsuno plots result in excellent linear correlation ($R^2$ = 0.995-0.997) with ${\rho}$ = 0.93-1.23 and r = 0.57-0.67, indicating that the negative deviation shown by substrates possessing an EDG is caused by ground-state stabilization through resonance interactions but not due to a change in ratedetermining step upon changing the nonleaving-group substituent X. The ${\rho}$ value increases as the incoming amine becomes more basic and more reactive, indicating that the RSP is not operative in the current reactions.

• Journal of the Korean Chemical Society
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• v.22 no.1
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• pp.30-36
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• 1978

The kinetics of hydrolysis of ${\alpha}$-nitrobenzaldehydephenylhydrazone derivatives (p-$NO_2$, m-$NO_2$, p-Cl, p-$CH_3$) have been investigated by UV spectrometry in 25% dioxane-water at $25^{\circ}C$ and a rate equation which can be applied over wide pH range was obtained. From the rate equation and the effect of solvent, substituent and pKa on the rate equation, the following reaction mechanisms were proposed. Below pH 3.0 the hydrolysis of ${\alpha}$-nitrobenzaldehydephenylhydrazone proceeds by $S_N1$ mechanism, while above pH 4.0 the hydrolysis proceeds through 1,3-dipole ion mechanism. In the range of pH from 3.0 to 4.0 these two reactions occur competitively.

• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.284-292
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• 1984

This paper aims to predict the substituent and Lewis acid catalysis effect or reactivity on the regioselectivity of (4+2) cycloaddition reaction of the substituted-E-arene-diazocyanides and nitrosobenzenes. Frontier orbital theory (FMO) has been applied to thermal and catalyzed Diels-Alder reaction by means of CNDO/2 and EHT-SPD methods. It has been found that: (1) The above reaction is positive rho(${\rho}$) values in Hammett equation, so it takes normal electron demand reaction, and four-frontier orbitals and Anh methods are identical with experimental major regioisomer.(2) When electron withdrawing radicals are substituted HOMO and LUMO energies of dienophiles are reduced, and the reactivity is increased. (3) The major regioisomer is predicted as B type, as the Lewis acid makes complexes of dienophile, and polaries LUMO coefficients of dienophile in an opposite way. (4) The linear correlation of Hammett is indicated in the graph of stabilized energies(${\Delta}$E) and sigma(${\sigma}$).