• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4403-4407
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• 2011

The nucleophilic substitution reactions of dipropyl chlorothiophosphate (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; $k_H/k_D$) are primary normal ($k_H/k_D$ = 1.11-1.35). A concerted mechanism involving predominant frontside nucleophilic attack is proposed on the basis of the primary normal DKIEs and selectivity parameters. Hydrogen bonded, four-center-type transition state is proposed. The steric effects of the two ligands on the anilinolysis rates of various substrates are discussed.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4387-4391
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• 2011

The kinetic studies on the pyridinolysis of diisopropyl thiophosphinic chloride have been carried out in acetonitrile at $55.0^{\circ}C$. The free energy correlations for substituent X variations in the X-pyridines are biphasic concave upwards with a break point at X = 3-Ph. A concerted SN2 mechanism is proposed with a change of the attacking direction of the X-pyridine from a frontside attack for the strongly basic pyridines to a backside attack for the weakly basic pyridines. The factors to determine the rates and thio effects on the rates for the pyridinolyses of thiophophinic chloride, chlorothiophosphate, phosphinic chloride, phosphonochloridothioate, and chlorophosphate systems are briefly reviewed on the basis of the magnitude of the positive charge of the reaction center P atom and steric effects of the two ligands.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2306-2310
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• 2011

The nucleophilic substitution reactions of diethyl thiophosphinic chloride 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 values of deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) invariably increase from secondary inverse ($k_H/k_D$ < 1) to primary normal (kH/kD > 1) as the nucleophiles change from the strongly basic to weakly basic anilines. The secondary inverse with the strongly basic anilines and primary normal DKIEs with the weakly basic anilines are rationalized by the gradual transition state (TS) variation from a predominant backside attack, via invariably increasing the fraction of a frontside attack, to a predominant frontside attack, in which the reaction mechanism is a concerted $S_N2$ pathway. A frontside attack involving a hydrogen bonded, four-center-type TS is substantiated by the primary normal DKIEs.

• Journal of the Korean Chemical Society
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• v.19 no.6
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• pp.443-448
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• 1975

A series of 9,10-dialkyl-9,10-dihydroanthracene has been dehydrogenated by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in good yields. The yield decreased with the larger alkyl groups in this 9,10-dialkyl-9,10-DHA series(DHA=dihydroanthracene). It is conceivable that trans-9,10-diisopropyl-9,10-DHA was dehydrogenated more rapidly than the cis-isomer, and, bassed on this observation, a concerted mechanism was ruled out and an ionic mechanism is proposed.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1096-1100
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• 2013

The kinetic studies on the reactions of O-methyl (1), O-propyl (3) and O-isopropyl (4) phenyl phosphonochloridothioates with substituted anilines and deuterated anilines have been carried out in acetonitrile at $55.0^{\circ}C$. A concerted $S_N2$ mechanism is proposed for the anilinolyses of 1, 3 and 4. The anilinolysis rates of the phosphonochloridothioates are predominantly dependent upon the steric effects over the inductive effects of the two ligands. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are primary normal with 1 and 3, while secondary inverse with 4. Primary normal and secondary inverse DKIEs are rationalized by frontside and backside nucleophilic attack transition state, respectively. The DKIEs of the phosphonochloridothioates do not have any consistent correlations with the two ligands.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1016-1022
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• 2014

The kinetic studies on the reactions of O-methyl N,N-diisopropylamino phosphonochloridothioate with X-anilines and X-pyridines have been carried out in acetonitrile. The free energy relationship with X in the anilines exhibits biphasic concave upwards with a break region between X = (H and 4-F), giving unusual negative ${\beta}_X$ and positive ${\rho}_X$ values with weakly basic anilines. The unusual phenomenon is rationalized by isokinetic relationship. A stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed based on the selectivity parameter and variation trend of the deuterium kinetic isotope effects with X. The free energy relationship with X in the pyridines exhibits biphasic concave upwards with a break point at X = 3-MeO. A concerted mechanism is proposed based on relatively small ${\beta}_X$ value, and frontside and backside nucleophilic attack are proposed with strongly and weakly basic pyridines, respectively.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1769-1773
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• 2008

fThe kinetics and mechanism of the reactions of Y-O-aryl phenylphosphonochloridothioates with X-pyridines are investigated in acetonitrile at 35.0 ${^{\circ}C}$. The negative value of the cross-interaction constant, $\rho$XY = −0.46, indicates that the reaction proceeds by concerted $S_N2$ mechanism. The observed $k_H/k_D$ values involving d-5 pyridine ($C_5D_5N$) nucleophiles are greater than unity (1.05-1.11). The net primary deuterium kinetic isotope effects, $(k_H/k_D)_{net}$ = 1.28-1.35, excluding the increased $pK_a$ effect of d-5 pyridine are obtained. The transition state with a hydrogen bond between the leaving group Cl and the hydrogen (deuterium) atom in the C-H(D) is suggested for the studied reaction system.

• Bulletin of the Korean Chemical Society
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• v.28 no.6
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• pp.936-940
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• 2007

The aminolyses of diphenyl phosphinic chloride (1) with substituted anilines in acetonitrile at 55.0 oC are investigated kinetically. Large Hammett ρ X (ρnuc = ?4.78) and Bronsted β X (βnuc = 1.69) values suggest extensive bond formation in the transition state. The primary normal kinetic isotope effects (kH/kD = 1.42-1.82) involving deuterated aniline (XC6H4ND2) nucleophiles indicate that hydrogen bonding results in partial deprotonation of the aniline nucleophile in the rate-limiting step. The faster rate of diphenyl phosphinic chloride (1) than diphenyl chlorophosphate (2) is rationalized by the large proportion of a frontside attack in the reaction of 1. These results are consistent with a concerted mechanism involving a partial frontside nucleophilic attack through a hydrogen-bonded, four-center type transition state.

• Journal of the Korean Chemical Society
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• v.21 no.3
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• pp.155-160
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• 1977

HMO correlation diagrams for some competing 1,2-and 1,4-cycloaddition reactions have been made to elucidate the reaction mechanism. The main conclusions obtained from this study are as follows. 1) The crossing between the highest occupied molecular orbital and the lowest unoccupied molecular orbital was not observed, which indicates that the reaction proceeds thermally, in agreement with the experimental results. 2) From the consideration of the energy barrier in the process of the energy transformation going from reactants to product, the two-step mechanism via a diradical intermediate is preferred over the concerted one. 3) The existance of diradical intermediates can account for the observed product distributions.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.985-990
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• 1994

Cross-interaction constants, ${\rho}^e_{XY}$, ${\rho}_{YZ}$ and ${\rho}_{XZ}$ are defined using observed rate constant, k_N=(k_1/k_{-1})k_2=Kk_2$, for the stepwise carbonyl addition reactions involving the rate-limiting breakdown of a tetrahedral intermediate $(T^{\pm})$. Abundant experimental evidence in the literature enables us to determine signs for the three constants for such mechanism, ${\rho}^e_{XY}$>0, ${\rho}_{YZ}$<0 and ${\rho}_{XZ}$0. These are in contrast to those for the concerted $S_N2$ mechanism, ${\rho}_{XY}$<0, ${\rho}_{YZ}$>0 and ${\rho}_{XZ}$, and provide useful mechanistic criteria. In the light of these criteria, mechanisms of some nucleophilic reactions of carbonyl compounds are re-examined.