We have designed and synthesized a series of new phthalimidopiperazines, biological activity test show that the target compounds(Ic, Ie, ii) can inhibit HIV-I RT with IC50 20.0, 43.8, and 63.7 mu M, respectively.
Oxidations of piperazine, 1-methylpiperazine and 1-ethylpiperazine by bromamine-T (BAT) in buffered acidic medium have been kinetically studied at 303 K. The reaction shows a first-order dependence of the rate each on...Oxidations of piperazine, 1-methylpiperazine and 1-ethylpiperazine by bromamine-T (BAT) in buffered acidic medium have been kinetically studied at 303 K. The reaction shows a first-order dependence of the rate each on [BAT]0 and [piperazine]0, and an inverse fractional-order dependence on [H+]. The additions of halide ions and the reduction product of BAT, p-toluenesulfonamide, have no effect on the reaction rate. The variation of ionic strength of the solvent medium has no influence on the rate. Activation parameters have been evaluated from the Arrhenius and Eyring plots. A common mechanism consistent with the kinetic data has been proposed for all piperazines. The protonation constants of substrates have been evaluated. The Hammett linear free-energy relationship has been observed for the reaction with ρ = ?0.5 indicating that the electron-donating groups enhance the reaction rate by stabilizing the transition state. An isokinetic relationship observed shows β = 368 K indicating the dominance of enthalpy factors on the reaction rate.展开更多
The second acidic dissociation constants of protonated piperazine-N,N′-bis-2-hydroxypropane-sulfonic acid (POPSO sesquisodium salt) have been determined at 12 different temperatures from (278.15 to 328.15) K includin...The second acidic dissociation constants of protonated piperazine-N,N′-bis-2-hydroxypropane-sulfonic acid (POPSO sesquisodium salt) have been determined at 12 different temperatures from (278.15 to 328.15) K including 310.15 K. Electromotive-force measurement technique was used employing hydrogen-silver chloride cells without liquid junction. The results of pK2 are given by the equation: pK2 = -1041.77/T + 51.0459 - 6.97646lnT. The uncertainty of the fit is ±0.0008. At 289.15 K, pK2 = 7.8029;whereas, at 310.15 K (body temperature), pK2 = 7.6862. Thus, the buffer solutions of POPSO and its sodium salt are useful for pH control in the physiological pH region of (7.0 to 8.5). The changes of Gibbs free energy (G°), enthalpy (H°), entropy (S°) and heat capacity Cp° were computed from the temperature derivative of the pK2 for the dissociation of the zwitterionic acid POPSO±-3 = POPSO-4 + H+ in the standard state. At 298.15 K, these results are compared with those of similar components, which are the derivatives of the parent compounds TAURINE, PIPERAZINE and MORPHOLINE.展开更多
Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range ...Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range from (278.15 to 328.15) K including the body temperature 310.15 K by measurement of the electromotive-force for cells without liquid junction of the type: Pt (s), H2 (g), 101.325 kPa|Na-PIPES (m1) + Na 2-PIPES (m2) + NaCl (m3)|AgCl (s), Ag (s), where m1, m2 and m3 indicate the molalities of the corresponding species at 1 atm = 101.325 kPa in SI units. The pK2 values for the dissociation of Na-PIPES are represented by the equation: pK2 = -1303.76/T + 48.369 - 6.46889 lnT with an uncertainty of ± 0.001. The values of pK2 for Na-PIPES were found to be 7.1399 ± 0.0004 at 298.15 K and 7.0512 ± 0.0004 at 310.15 K, respectively, and indicate that this buffer would be useful as pH standard in the range of physiological application. Standard thermodynamic quantities for the acidic dissociation process of Na-PIPES have been derived from the temperature coefficients of the pK2. These values are compared with those of structurally related N-substituted PIPERAZINE and TAURINE at 298.15 K.展开更多
文摘We have designed and synthesized a series of new phthalimidopiperazines, biological activity test show that the target compounds(Ic, Ie, ii) can inhibit HIV-I RT with IC50 20.0, 43.8, and 63.7 mu M, respectively.
文摘Oxidations of piperazine, 1-methylpiperazine and 1-ethylpiperazine by bromamine-T (BAT) in buffered acidic medium have been kinetically studied at 303 K. The reaction shows a first-order dependence of the rate each on [BAT]0 and [piperazine]0, and an inverse fractional-order dependence on [H+]. The additions of halide ions and the reduction product of BAT, p-toluenesulfonamide, have no effect on the reaction rate. The variation of ionic strength of the solvent medium has no influence on the rate. Activation parameters have been evaluated from the Arrhenius and Eyring plots. A common mechanism consistent with the kinetic data has been proposed for all piperazines. The protonation constants of substrates have been evaluated. The Hammett linear free-energy relationship has been observed for the reaction with ρ = ?0.5 indicating that the electron-donating groups enhance the reaction rate by stabilizing the transition state. An isokinetic relationship observed shows β = 368 K indicating the dominance of enthalpy factors on the reaction rate.
文摘The second acidic dissociation constants of protonated piperazine-N,N′-bis-2-hydroxypropane-sulfonic acid (POPSO sesquisodium salt) have been determined at 12 different temperatures from (278.15 to 328.15) K including 310.15 K. Electromotive-force measurement technique was used employing hydrogen-silver chloride cells without liquid junction. The results of pK2 are given by the equation: pK2 = -1041.77/T + 51.0459 - 6.97646lnT. The uncertainty of the fit is ±0.0008. At 289.15 K, pK2 = 7.8029;whereas, at 310.15 K (body temperature), pK2 = 7.6862. Thus, the buffer solutions of POPSO and its sodium salt are useful for pH control in the physiological pH region of (7.0 to 8.5). The changes of Gibbs free energy (G°), enthalpy (H°), entropy (S°) and heat capacity Cp° were computed from the temperature derivative of the pK2 for the dissociation of the zwitterionic acid POPSO±-3 = POPSO-4 + H+ in the standard state. At 298.15 K, these results are compared with those of similar components, which are the derivatives of the parent compounds TAURINE, PIPERAZINE and MORPHOLINE.
文摘Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range from (278.15 to 328.15) K including the body temperature 310.15 K by measurement of the electromotive-force for cells without liquid junction of the type: Pt (s), H2 (g), 101.325 kPa|Na-PIPES (m1) + Na 2-PIPES (m2) + NaCl (m3)|AgCl (s), Ag (s), where m1, m2 and m3 indicate the molalities of the corresponding species at 1 atm = 101.325 kPa in SI units. The pK2 values for the dissociation of Na-PIPES are represented by the equation: pK2 = -1303.76/T + 48.369 - 6.46889 lnT with an uncertainty of ± 0.001. The values of pK2 for Na-PIPES were found to be 7.1399 ± 0.0004 at 298.15 K and 7.0512 ± 0.0004 at 310.15 K, respectively, and indicate that this buffer would be useful as pH standard in the range of physiological application. Standard thermodynamic quantities for the acidic dissociation process of Na-PIPES have been derived from the temperature coefficients of the pK2. These values are compared with those of structurally related N-substituted PIPERAZINE and TAURINE at 298.15 K.
