Cd, Zn-thionelns were isolated from the rat liver by improved Winge method and purified further. The composition was determined. The mobilization of Cd ions from the Cd, Zn-metallothioneins was studied with spectropho...Cd, Zn-thionelns were isolated from the rat liver by improved Winge method and purified further. The composition was determined. The mobilization of Cd ions from the Cd, Zn-metallothioneins was studied with spectrophotometric method. The results show that the reaction of DTP A or EDTA with Cd, Zn-thioneins occurs through three steps. The first step follows pseudo-first order reaction with association mechanism. The formation constants and the dissociation rate constants of the relevant intermediate ternary complexes and apparent rate constants, Kapp were determined. The properties and structure of Cd, Zn-thioneins and ligands with low molecular weights affect the values of Kapp.展开更多
The kinetics of PTC-Wittig reaction between substituted aromatic aldehydes and 2-butenyl methyldiphenylphosphonium salt has been studied. The low reaction constant (ρ=0. 30) implies that these PTC-Wittig reactions ta...The kinetics of PTC-Wittig reaction between substituted aromatic aldehydes and 2-butenyl methyldiphenylphosphonium salt has been studied. The low reaction constant (ρ=0. 30) implies that these PTC-Wittig reactions take place through low polar intermediate.展开更多
The kinetic behaviors of Wittig Horner reaction between α naphthylmethyl dibutyl phosphate and substituted benzaldehydes have been investigated.The mechanism of the reaction is discussed on the basis of the rate cons...The kinetic behaviors of Wittig Horner reaction between α naphthylmethyl dibutyl phosphate and substituted benzaldehydes have been investigated.The mechanism of the reaction is discussed on the basis of the rate constant k,Hammett ρ,correlative coefficient r,ΔS ≠.The yields of the competing reactions between benzaldehyde and p nitrobenzaldehyde and lihewis studied by the way..展开更多
The reaction 1-(1-hydroxybenzotriazolyl)-2,4-dinitrobenzene 1 and 2-(1-hydroxybenzotriazolyl)-5-nitro-pyridine 2 with amines undergoes amination followed by elimination of the 1-hydroxyl benzotriazolyl anion. The kine...The reaction 1-(1-hydroxybenzotriazolyl)-2,4-dinitrobenzene 1 and 2-(1-hydroxybenzotriazolyl)-5-nitro-pyridine 2 with amines undergoes amination followed by elimination of the 1-hydroxyl benzotriazolyl anion. The kinetic data for the reaction of 1 and 2 with Mo, CHA and An in MeOH and AN proceeded by uncatalysed mechanism in which the rate limiting step is the leaving group departure, whereas the reaction with Mo in toluene proceeded by uncatalysed mechanism in which the formation of the zwitterionic intermediate is the rate determining step. While the reactions of 1 with CHA and An and the reaction of 2 with CHA in toluene proceeded by SB mechanism in which the rate determining step is the proton transfer process. The reactions of 1 and 2 with Mo in the three solvents and with CHA and An in MeOH and AN is greatly depended on the stability of the zwitterionic intermediate. The effect of ring activation is due to the ground state stabilization and the more efficient delocalization of the negative charge with a nitro group than with a ring-nitrogen in the transition state. The low activation enthalpies ΔH# and the highly negative activation entropies ΔS# are due to the intramolecular hydrogen bonding with the ammonio hydrogen present in the transition state.展开更多
基金This study was supported by National Natural Science Foundation of China.
文摘Cd, Zn-thionelns were isolated from the rat liver by improved Winge method and purified further. The composition was determined. The mobilization of Cd ions from the Cd, Zn-metallothioneins was studied with spectrophotometric method. The results show that the reaction of DTP A or EDTA with Cd, Zn-thioneins occurs through three steps. The first step follows pseudo-first order reaction with association mechanism. The formation constants and the dissociation rate constants of the relevant intermediate ternary complexes and apparent rate constants, Kapp were determined. The properties and structure of Cd, Zn-thioneins and ligands with low molecular weights affect the values of Kapp.
文摘The kinetics of PTC-Wittig reaction between substituted aromatic aldehydes and 2-butenyl methyldiphenylphosphonium salt has been studied. The low reaction constant (ρ=0. 30) implies that these PTC-Wittig reactions take place through low polar intermediate.
文摘The kinetic behaviors of Wittig Horner reaction between α naphthylmethyl dibutyl phosphate and substituted benzaldehydes have been investigated.The mechanism of the reaction is discussed on the basis of the rate constant k,Hammett ρ,correlative coefficient r,ΔS ≠.The yields of the competing reactions between benzaldehyde and p nitrobenzaldehyde and lihewis studied by the way..
文摘The reaction 1-(1-hydroxybenzotriazolyl)-2,4-dinitrobenzene 1 and 2-(1-hydroxybenzotriazolyl)-5-nitro-pyridine 2 with amines undergoes amination followed by elimination of the 1-hydroxyl benzotriazolyl anion. The kinetic data for the reaction of 1 and 2 with Mo, CHA and An in MeOH and AN proceeded by uncatalysed mechanism in which the rate limiting step is the leaving group departure, whereas the reaction with Mo in toluene proceeded by uncatalysed mechanism in which the formation of the zwitterionic intermediate is the rate determining step. While the reactions of 1 with CHA and An and the reaction of 2 with CHA in toluene proceeded by SB mechanism in which the rate determining step is the proton transfer process. The reactions of 1 and 2 with Mo in the three solvents and with CHA and An in MeOH and AN is greatly depended on the stability of the zwitterionic intermediate. The effect of ring activation is due to the ground state stabilization and the more efficient delocalization of the negative charge with a nitro group than with a ring-nitrogen in the transition state. The low activation enthalpies ΔH# and the highly negative activation entropies ΔS# are due to the intramolecular hydrogen bonding with the ammonio hydrogen present in the transition state.
