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.

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.

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.

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.

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.

QSPR Studies on Impact Sensitivities of High Energy Density Molecules

이해황,Chang Kon Kim,Jun Li,조수경,김찬경 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.12

Impact sensitivity, one of the most important screening factors for novel high energy density materials (HEDMs), was predicted by use of quantitative structure-property relationship (QSPR) based on the electrostatic potential (ESP) values calculated on the van der Waals molecular surface (MSEP). Among various 3D descriptors derived from MSEP, we utilized total and positive variance of MSEP, and devised a new QSPR equation by combining three other parameters. We employed 37 HEDMs bearing a benzene scaffold and nitro substituents, which were also utilized by Rice and Hare. All the molecular structures were optimized at the B3LYP/6-31G(d) level of theory and confirmed as minima by the frequency calculations. Our new QSPR equation provided a good result to predict the impact sensitivities of the molecules in the training set including zwitterionic molecules.

Kinetics and Mechanism of the Pyridinolysis of Bis(2,6-dimethylphenyl) Chlorophosphate in Acetonitrile

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

The nucleophilic substitution reactions of bis(2,6-dimethylphenyl) chlorophosphate (5), containing the four ortho-methyl substituents, with X-pyridines are investigated kinetically in MeCN at 65.0 oC. The free energy correlations for substituent X variations in the nucleophiles exhibit biphasic concave upwards with a breakpoint at a X = 3-Cl. Unusual positive ρX (= +5.40) and negative βX (= –0.83) values are obtained with the weakly basic pyridines. The pyridinolysis rate of 5 is hundreds times slower compared to that of bis(phenyl)chlorophosphate because of the steric hindrance of the four ortho-methyl substituents in the two phenyl rings. Ion-pair mechanism is proposed and positive ρX and negative βX values are substantiated by an imbalance of the transition state.

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.

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.

Kinetics and Mechanism of the Anilinolysis of Bis(N,N-dimethylamino) Phosphinic Chloride in Acetonitrile

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

The nucleophilic substitution reactions of bis(N,N-dimethylamino) phosphinic chloride (3) with substituted anilines (XC_6H_4NH_2) and deuterated anilines (XC_6H_4ND_2) are investigated kinetically in acetonitrile at 65.0^oC. The anilinolysis rate of 3 is rather slow to be rationalized by the conventional stereoelectronic effects. The magnitudes of ρX (= –6.42) and βX (= 2.27) values are exceptionally great. The deuterium kinetic isotope effects (DKIEs; kH/kD) are secondary inverse (kH/kD = 0.69-0.96). A concerted SN2 mechanism involving a backside attack is proposed on the basis of secondary inverse DKIEs and the variation trend of the kH/kD values with X. The anilinolyses of six phosphinic chlorides in MeCN are briefly reviewed by means of DKIEs, steric effects of the two ligands, positive charge of the reaction center phosphorus atom, and selectivity parameters to obtain systematic information on phosphoryl transfer reaction mechanism.