• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.221-224
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• 2002

Nucleophilic addition reactions of benzylamines (BA; $XC_6H_4CH_2NH_2$) to ethyl-${\alpha}$-cyanocinnamates (ECC;$YC_6H_4CH$=C(CN)COOEt) have been investigated in acetonitrile at $30.0^{\circ}C$. The rate is first order with respect to BA and ECC. The rate is slower than that expected from the additive effect of ${\sigma}^-$ or $R^-$ for the activating groups (CN and COOEt). Natural. bond orbital ${\pi}^{\ast}_{c=c}$ calculations show that the contribution of COOEt group may not be fully effective despite the coplanar molecular structure. The selectivity parameters including the cross-interaction constant (${\rho}_{xy}$ = -0.22) indicate that the addition occurs in a single step. The kinetic isotope effects ($k_H/k_D$=2.5-2.8) involving deuterated BA ($XC_6H_4CH_2ND_2$) nucleophiles and activation parameters (${\Delta}H^{\neq}=4{\sim}6\;kcal\;mol^{-1};{\Delta}S^{\neq}=-45{\sim}-52\;e.u.$) suggest a cyclic transition state in which N-$C_{\alpha}$ and H-$C_{\beta}$ bonds are formed concurrently.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1897-1901
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• 2011

This report shows the rates of solvolyses for phenyl methanesulfonyl chloride ($C_6H_5CH_2SO_2Cl$, I) in ethanol, methanol, and aqueous binary mixtures incorporating ethanol, methanol, acetone, 2,2,2-trifluroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) are reported. Three representative solvents, studies were made at several temperatures and activation parameters were determined. The thirty kinds of solvents gave a reasonably precise extended Grunwald-Winstein plot, coefficient (R) of 0.954. The sensitivity values (l = 0.61 and m = 0.34, l/m = 1.8) of phenyl methanesulfonyl chloride (I) were smaller than those obtained for benzenesulfonyl chloride ($C_6H_5SO_2Cl$, II; l = 1.01 and m = 0.61) and 2-propanesulfonyl chloride ($(CH_3)_2CHSO_2Cl$, III; l = 1.28 and m = 0.64). As with the two previously studied solvolyses, an $S_N2$ pathway with somewhat ionization reaction is proposed for the solvolyses of I. The activation parameters, ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$, were determined and they are also in line with values expected for a bimolecular reaction mechanism. The kinetic solvent isotope effect of 2.34 in $CH_3OH/CH_3OD$ is in accord with a bimolecular mechanism, probably assisted by general-base catalysis.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.699-703
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• 2004

Solvolyses of isopropylsulfonyl chloride (IPSC) in water, D_2O,\;CH_3OD$, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25, 35 and 45$^{\circ}C$. The Grunwald-Winstein plot of first-order rate constants for the solvolytic reaction of IPSC with $Y_{Cl}$ (based on 2-adamantyl chloride) shows marked dispersions into three separate lines for three aqueous mixtures with a small slope (m < 0.30). The extended Grunwald-Winstein plots for the solvolysis of IPSC show better correlation. The kinetic solvent isotope effects determined in water and methanol are in consistent with the proposed mechanism of the general base catalyzed and/or $S_AN/S_N2$ reaction mechanism for IPSC solvolyses based on mass law and stoichiometric solvation effect studies.

• Journal of the Korean Chemical Society
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• v.61 no.1
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• pp.25-28
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• 2017

Solvolyses with the reaction center being the sulfur of 4-(chlorosulfonyl)biphenyl ($C_6H_5C_6H_4SO_2Cl$, 1) was studied under solvolytic conditions and the extended Grunwald-Winstein equation was applied. The thirty five kinds of solvents gave a reasonable extended Grunwald-Winstein plot with a correlation coefficient (R) of 0.940. The sensitivity values (l = 0.60 and m = 0.47) of 1 were smaller than those obtained for benzenesulfonyl chloride ($C_6H_5SO_2Cl$, 2; l = 1.10 and m = 0.61) proposed to undergo dissociative $S_N2$ mechanism. These l and m values for the solvolyses of 1 can be considered to support a $S_N2$ pathway with some ionization reaction. The activation parameters, ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$, were determined and they are also in line with values expected for a bimolecular reaction. The kinetic solvent isotope effect (KSIE) of 1.26 is also in accord with a bimolecular mechanism, probably assisted by general-base catalysis.

• Bulletin of the Korean Chemical Society
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• v.26 no.6
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• pp.935-938
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• 2005

Nucleophilic addition reactions of benzylamines (BA; $XC_6H_4CH_2NH_2$) to $\alpha-cyano-\beta$-phenylacrylamides (CPA; $YC_6H_4CH=C(CN)CONH_2$) have been investigated in acetonitrile at 25.0 ${^{\circ}C}$. The rate is first order with respect to BA and CPA and no base catalysis is observed. The addition of BA to CPA occurs in a single step in which the addition of BA to $C_{\beta}$ of CPA and proton transfer from BA to $C_{\alpha}$ of CPA take place concurrently with a four-membered cyclic transition state structure. The magnitude of the Hammett ($\rho_X$) and Bronsted ($\beta_X$) coefficients are rather small suggesting an early tansition state (TS). The sign and magnitude of the crossinteraction constant, $\rho_XY$ (= −D0.26), is comparable to those found in the normal bond formation processes in the $S_N2$ and addition reactions. The normal kinetic isotope effect ($k_H/k_D\;{\gt}$ 1.0) and relatively low ${\Delta}H^{\neq}$ and large negative ${\Delta}S^{\neq}$ values are also consistent with the mechanism proposed.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4117-4121
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• 2012

The solvolysis rate constants of allyl chloroformate ($CH_2=CHCH_2OCOCl$, 3) in 30 different solvents are well correlated with the extended Grunwald-Winstein equation, using the $N_T$ solvent nucleophilicity scale and $Y_{Cl}$ solvent ionizing scale, with the sensitivity values of $0.93{\pm}0.05$ and $0.41{\pm}0.02$ for l and m, respectively. These l and m values can be considered to support a $S_N2$ reaction pathway. The activation enthalpies (${\Delta}H^{\neq}$) were 12.5 to 13.4 $kcal{\cdot}mol^{-1}$ and the activation entropies (${\Delta}S^{\neq}$) were -34.4 to -37.3 $cal{\cdot}mol^{-1}{\cdot}K^{-1}$, which is also consistent with the proposed bimolecular reaction mechanism. The solvent kinetic isotope effect (SKIE, $k_{MeOH}/k_{MeOD}$) of 2.16 was also in accord with the $S_N2$ mechanism. The values of product selectivity (S) for the solvolyses of 3 in alcohol/water mixtures was 1.3 to 3.9, which is also consistent with the proposed bimolecular reaction mechanism.

• 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.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.663-669
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• 2012

The nucleophilic substitution reactions of dibutyl chlorophosphate (3) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $55.0^{\circ}C$. The obtained deuterium kinetic isotope effects (DKIEs; kH/kD) are secondary inverse ($k_H/k_D$ = 0.86-0.97) with the strongly basic anilines while primary normal ($k_H/k_D$ = 1.04-1.10) with the weakly basic anilines. The DKIEs, steric effects of the two ligands, activation parameters, cross-interaction constants, variation trends of the kH/kD values with X, and mechanism are discussed for the anilinolyses of the nine ($R_1O$)($R_2O$)P(=O)Cl-type chlorophosphates. A concerted mechanism is proposed with a backside nucleophilic attack transition state for the strongly basic anilines and with a frontside attack involving a hydrogen-bonded four-center-type transition state for the weakly basic anilines on the basis of the magnitudes, secondary inverse and primary normal, and variation trends of the $k_H/k_D$ values with X.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.1037-1041
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• 2012

The nucleophilic substitution reactions of (2R,4R,5S)-(+)-2-chloro-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholidine 2-sulfide (3) 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 3 involving a cyclic five-membered ring is considerably fast because of small negative value of the entropy of activation (${\Delta}S^\neq=-2cal\;mol^{-1}\;K^{-1}$) over considerably unfavorable enthalpy of activation (${\Delta}H^\neq=18.0\;kcal\;mol^{-1}$). Great enthalpy and small negative entropy of activation are ascribed to sterically congested transition state (TS) and bulk solvent structure breaking in the TS. A concerted $S_N2$ mechanism with a backside nucleophilic attack is proposed on the basis of the secondary inverse deuterium kinetic isotope effects, $k_H/k_D$ < 1.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2628-2632
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• 2011

The nucleophilic substitution reactions of Y-O-aryl phenyl phosphonochloridothioates with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are kinetically investigated in acetonitrile at $55.0^{\circ}C$. The deuterium kinetic isotope effects (DKIEs) invariably increase from an extremely large secondary inverse ($k_H/k_D$ = 0.439; min) to a primary normal ($k_H/k_D$ = 1.34; max) as both substituents of nucleophile (X) and substrate (Y) change from electron-donating to electron-withdrawing. These results are opposite to the DKIEs on Y-O-aryl methyl phosphonochloridothioates, and can be rationalized by the gradual transition state (TS) variation from backside to frontside attack. The trigonal bipyramidal pentacoordinate TS is proposed for a backside attack, while the hydrogen-bonded, four-center-type TS is proposed for a frontside attack. The negative values of the cross-interaction constants (${\rho}_{XY(H)}$ = -0.38 for $XC_6H_4NH_2$ and ${\rho}_{XY(D)}$ = -0.29 for $XC_6H_4ND_2$) indicate that the reactions proceed by a concerted $S_N2$ mechanism.