羧酸酯水解与氨解反应的胶团催化研究

An Investigation on the Micelle-Catalytic Hydrolysis and Ammonolysis of Carboxylic Acid Esters

较系统地研究了在有氨和无氨缓冲体系中pH变化对羧酯脱酰反应速度和胶团催化作用的影响．提供在两种缓冲体系中反应速度随溶液pH变化的规律．结果表明CTAB胶团对对硝基本酚丙酸酯和乙酸酯碱水解反应的催化效率随溶液pH上升而削弱．对硝基本酚丙酸酯和乙酸酯在含氨的缓冲体系中有水解和氨解反应同时进行．CTAB胶团对水解反应有正催化作用，而对氨解反应则显示负催化作用．这使得NH3－NH4Br缓冲体系中CTAB胶团对体系总反应速度的影响随溶液pH降低从正催化变为负催化．

The deacylation reactions ofp-nitrophenyl propionate and acetate in buffered aqueous solution with and without am-monia and the effects of cetyltrimethylanunnium brothede (CTAB) dricelle on them have been investigated. The pseudo first order rate constant of the deacylation reaction in the buffer with ammnia shows higher value than that in the buffer of the same pH but without imonia. CTAB Ancelles show positive catalysis on the reaction in the system without anunonia no matter what pH is. But in systems including ammonia, CTAB Ancelle shows catalytic effect at high pH and negative catalytic effect when the pH is lower than 9.6. These interesting phenomena have been attributed to that the mechanism of deacylation reaction in buffer with and without aJmmnia are different. Only hydrolysis occurs in the systems without ammonia, whereas both hydrolysis and anwnnolysis exist in the systems with amxnonia. Actually, CTAB dricelle can only enhance the reaction rate of hydrolysis but reduce that of arnmonolysis.