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        • KCI등재

          Kinetics and Mechanism of the Pyridinolysis of Methyl Phenyl Phosphinic Chloride in Acetonitrile

          이해황,어디까리 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.6

          The pyridinolysis of methyl phenyl phosphinic chloride is investigated kinetically in acetonitrile at –20.0 ^oC. The Hammett and Brönsted plots for substituent X variations in the nucleophiles are biphasic concave downwards with a break point at X = H, and unusual positive ρX (= 2.94) and negative βX (= –0.48) values are obtained for the strongly basic nucleophiles. A stepwise mechanism with a rate-limiting step change from bond breaking for the weakly basic pyridines to bond formation for the strongly basic pyridines is proposed on the basis of biphasic concave downward Hammett and Brönsted plots. Unusual positive ρ_X and negative β_X values are rationalized by the isokinetic relationship. The pyridinolyses and anilinolyses of four R_1R_2P(=O)Cl-type substrates, dimethyl, diethyl, methyl phenyl, and diphenyl phosphinic chlorides in acetonitrile are compared to obtain systematic information on phosphoryl transfer reaction mechanism. The combination of the two ligands,Me and Ph, shows unexpected kinetic results for both the anilinolysis and pyridinolysis: greatest magnitude of k_H/k_D (= 2.10) involving deuterated anilines [XC_6H_4NH_2(D_2)] for the anilinolysis, and exceptionally fast rate and biphasic concave downward free energy correlation for the pyridinolysis.

        • SCOPUSKCI등재

          2,4-이니트로 할로벤젠과 치환된 아닐린의 반응속도에 대한 용매효과 (제1보)

          이해황,이익춘,Hai Whang Lee,Ikchoon Lee Korean Chemical Society 1977 대한화학회지 Vol.21 No.2

          2,4-이니르로 염화벤젠과 p-톨루이딘, 아닐린 및 p-염화아닐린간의 반응속도론적인 연구를 메탄올-아세트니트릴 혼합용매에서 실시하였다. 알코올의 수소에 의한 특수용매화로 실험결과를 해석하였으며, 용매의 변화에 따라 반응메카니즘이 변함을 알았다. Kinetic studies on the rates of reactions of 2, 4-dinitrochlorobenzene with p-toluidine, aniline and p-chloroaniline in $CH_3CH-CH_3OH$ binary solvent mixtures have been carried out. The experimental results have been explained in terms of the specific solvation by alcoholic hydrogen. It has been shown that the bond breaking step is rate determining in the solvent system studied and the energy barrier is getting low as the solvent changes from acetonitrile to methanol.

        • KCI등재

          Kinetics and Mechanism of the Pyridinolysis of Diisopropyl Thiophosphinic Chloride in Acetonitrile

          이해황,Md. Ehtesham Ul Hoque 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.12

          The kinetic studies on the pyridinolysis of diisopropyl thiophosphinic chloride have been carried out in acetonitrile at 55.0 ^oC. 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 S_N2 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.

        • SCOPUSKCI등재

          Effects of Medium on Nucleophilic Substitution Reactions (I). Methanolysis of t-Butylbromide and Benzoylchloride in Methanol-Acetonitrile Mixtures

          이해황,나상무,이익춘,Hai Whang Lee,Sangmoo La,Ikchoon Lee Korean Chemical Society 1980 대한화학회지 Vol.24 No.2

          A kinetic study of the methanolysis of t-butylbromide and benzoylchloride in methanol-acetonitrile mixtures is reported. First order rate constants for the methanolysis of t-butyl bromide show maximum at $X_{MeOH}$=0.75∼0.9 and 25∼$50^{\circ}C$. Apparent second order rate constants for the methanolysis of benzoylchloride also show maximum at $X_{MeOH}$= 0.6∼0.95 and 12∼$26^{\circ}C$. The maximum rate is ascribed to the solvent structure change; the addition of acetonitrile to methanol perturbs the methanol structure increasing the free methanol molecules available to stabilize the transition state for the methanolysis of t-butylbromide and benzoylchloride. It has been shown that methanol acts as nucleophilic and electrophilic catalyst upon methanolysis of t-butylbromide and as electrophilic catalyst upon methanolysis of benzoylchloride. t-Butylbromide와 benzoylchloride의 가메탄올 분해반응을 메탄올-아세토니트릴 혼합용매하에서 연구하였다. t-Butylbromide의 가메탄올 분해반응 일차속도상수는 온도 변화가 25∼$50^{\circ}C$일때 메탄올의 몰분율 0.75∼0.9 부근에서 최대치를 보였다. Benzoylchloride의 경우에는 겉보기 2차 반응속도 상수가 온도 변화 12∼$26{\circ}C$일때 메탄올의 몰분율 0.6∼0.75에서 역시 최대치를 보였다. 최대속도는 용매구조 변화에 기인함을 알았는데 메탄올에 아세토니트릴이 첨가됨에 따라 자유 메탄올 분자가 증가하여 t-butylbromide 및 benzoylchloride의 가메탄올 분해반응에서 천이상태의 안정화에 기여함을 알았다. 메탄올은 t-butylbromide의 가메탄올 분해반응의 경우 친전자 및 친핵 촉매작용을, benzoylchloride의 가메탄올 분해반응의 경우에는 친전자 촉매작용을 함을 알았다.

        • KCI등재

          Kinetics and Mechanism of the Anilinolysis of Dipropyl Chlorothiophosphate in Acetonitrile

          이해황,Md. Ehtesham Ul Hoque 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.12

          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 ^oC. The obtained deuterium kinetic isotope effects (DKIEs; kH/kD) are primary normal (kH/kD = 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.

        • KCI등재

          Kinetics and Mechanism of the Benzylaminolysis of O,O-Dimethyl S-Aryl Phosphorothioates in Dimethyl Sulfoxide

          이해황,Hasi Rani Barai,어디까리 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.12

          Kinetic studies of the reactions of O,O-dimethyl Z-S-aryl phosphorothioates with X-benzylamines have been carried out in dimethyl sulfoxide at 85.0 °C. The Hammett (log k2 vs σX) and Brönsted [log k2 vs pKa(X)] plots for substituent X variations in the nucleophiles are discrete with a break region between 4-Me and H, while the Hammett plots (log k2 vs σZ) for substituent Z variations in the leaving groups are linear. The sign of the crossinteraction constant (ρXZ) is positive for both the strongly and weakly basic nucleophiles. Greater magnitude of ρXZ (= 2.54) value is observed with the weakly basic nucleophiles compared to with the strongly basic nucleophiles (ρXZ = 0.17). The deuterium kinetic isotope effects (kH/kD) involving deuterated benzylamines [XC6H4CH2ND2] are primary normal (kH/kD > 1). The proposed mechanism is a stepwise with a rate-limiting leaving group expulsion from the intermediate involving a frontside nucleophilic attack with a hydrogen bonded, four-center-type transition state for both the strongly and weakly basic nucleophiles.

        • SCOPUSKCI등재

          2,4-이니트로할로벤젠과 치환된 아닐린의 반응속도에 대한 용매효과 (제3보)

          이해황,이익춘,Hai Whang Lee,Ikchoon Lee Korean Chemical Society 1978 대한화학회지 Vol.22 No.4

          Rates of reactions of 2,4-dinitrofluorobenzene and 2,4-dinitrobromobenzene with para substituted anilines in acetonitrile-methanol binary mixtures have been measured. It has been shown that methanol acts as nucleophilic catalyst upon reaction of 2,4-dinitrobromobenzene with anilines and as bifunctional catalyst upon reaction of 2,4-dinitrofluorobenzene with anilines. The electrophilic catalysis by methanol probably consists of formation of hydrogen bond in the transition state between alcoholic hydrogen and leaving group, fluorine. Nucleophilic catalysis by methanol may be ascribed to formation of hydrogen bond between alcoholic oxygen and amine hydrogen in the transition state. 2,4-Dinitrohalo (F,Br) benzene과 파라치환아닐린간의 반응속도를 아세토니트릴-메탄올 혼합용매하에서 측정하였다. 2,4-Dinitrobromobenzene과 치환아닐간의 반응에서 메탄올은 친핵촉매 현상만을 보였으며, 2,4-dinitrofluorobenzene과 치환아닐린간의 반응에서는 메탄올은 양쪽성(친핵 및 친전자) 촉매현상을 보였다. 메탄올에 의한 친핵촉매현상은 아마도 천이상태에서 알코올기의 수소와 이탈기의 플루오르사이의 수소결합에 의해 설명될 수 있으며 친전자촉매현상은 알코올기의 산소와 아닐린의 아민기 수소사이의 수소결합에 기인되는 것임을 알았다.

        • SCOPUSKCI등재

          2,4-이니트로할로벤젠과 치환된 아닐린의 반응속도에 대한 용매효과 (제2보)

          이해황,이익춘,Hai Whang Lee,Ikchoon Lee Korean Chemical Society 1978 대한화학회지 Vol.22 No.1

          이니트로요오도벤젠과 파라치환체 아닐린과의 반응을 아세토니트릴-메탄올 혼합용매에서 연구하였다. 행해진 반응에서의 반응속도 상수는 메탄올 용매하에서 아세토니트릴 용매에 비해 큰 값을 보였다. 실험 결과로 부터 중간체 생성 과정이 반응속도 결정 단계임을 알았으며 용매효과는 메탄올의 산소 원자와 아닐린의 수소원자 사이의 수소결합에 의한 천이상태 안정화로 설명하였다. The reactions of 2,4-dinitroiodobenzene with para subtituted anilines in acetonitrile-methanol binary solvent mixtures have been studied. Rate constants for reactions in methanol rich solvents are greater than for reactions in acetonitrile rich solvents. Kinetic results show that the bond formation step is rate determining in the solvent system studied. The solvent effect can be explained by stabilization of the transition state by formation of hydrogen bond between oxygen atom of methanol and hydrogen atom of aniline.

        • KCI등재

          Kinetics and Mechanism of the Pyridinolysis of Ethylene Phosphorochloridate in Acetonitrile

          이해황,하시라니바라이 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.12

          The nucleophilic substitution reactions of ethylene phosphorochloridate (2) with X-pyridines are investigated kinetically in acetonitrile at –20.0 ^oC. The free energy correlations for substituent X variations in the nucleophiles exhibit biphasic concave upwards with a break point at X = 3_-Ph. Unusual positive ρX (= +2.49)and negative βX (= –0.41) values are obtained with the weakly basic pyridines, and rationalized by the isokinetic relationship with isokinetic temperature at tISOKINETIC = 6.6 ^oC. The pyridinolysis rate of 2 with a cyclic five-membered ring is forty thousand times faster than its acyclic counterpart (3: diethyl chlorophosphate) because of great positive value of the entropy of activation of 2 (ΔS^≠ = +49.2 eu) compared to negative value of 3 (ΔS≠ = –44.1 eu) over considerably unfavorable enthalpy of activation of 2 (ΔH≠ =28.4 kcal mol^–1) compared to 3 (ΔH≠ = 6.3 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. A concerted mechanism involving a change of nucleophilic attacking direction from a frontside attack with the strongly basic pyridines to a backside attack with the weakly basic pyridines is proposed.

        • KCI등재

          Kinetics and Mechanism of the Anilinolysis of Ethylene Phosphorochloridate in Acetonitrile

          이해황,하시라니바라이 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.12

          The nucleophilic substitution reactions of ethylene phosphorochloridate (1c) with substituted anilines (XC6H4NH2) and deuterated anilines (XC6H4ND2) are investigated kinetically in acetonitrile at 5.0 oC. 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 (ΔS≠= +30 cal mol–1 K–1) compared to negative value of 1a (ΔS≠ = –45 cal mol–1 K–1) over considerably unfavorable enthalpy of activation of 1c (ΔH≠ = 27.7 kcal mol–1) compared to 1a (ΔH≠ = 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 (kH/kD < 1) with the strongly basic anilines and primary normal (kH/kD > 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 SN2 mechanism is proposed and the primary normal deuterium kinetic isotope effects are substantiated by a hydrogen bonded, four-center-type TS.

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