阳离子表面活性剂胶团催化的活化热力学参数

测定了在9种阳离子表面活性剂胶团溶液中2,4—二硝基氯苯(DNCB)碱性水解 的速率常数,计算了这些过程的活化热力学参数。结果是：(1)DNCB在阳离子表面 活性剂胶团溶液中碱性水解反应的活化自由能△G^≠均比在纯水中降低。(2)活化 焓△A^≠和活化熵△S^≠显著降低。（3)活化熵△S^≠均为负值,活化熵的降低对 △G^≠的减小不利。(4)胶团催化反应速率常数的变化主要是由△G^≠决定,△G^ ≠是△H^≠和△S^≠大小的综合结果。

Thermodynamic Parameters of Activation for Hydrolysis of 2,4- Dinitrochlorobenzene Catalyzed by Cationic Micelles

Apparent rates of hydrolysis of 2, 4-dinitrochlorobezene (DNCB) catalyzed by nine cationic surfactants were determined and the thermodynamic parameters of activation were calculated. The results indicate that: (1) The free energies of activation, ΔG≠ , for hydrolysis of DNCB in the solutions of cationic surfactants are lower than those in water. (2) The enthalpies of activation, ΔH≠ , and the entropies of activation, AS5"6 are reduced by the cationic micelles. (3) The entropies of activation, ΔS≠ , are negative, which is favorable for the presence of more stable activation complex. (4) The rates of hydrolysis of DNCB is decided byΔG≠. The compensation effect of enthalpy-entropy has been envisaged.