kA−[A−] The results indicate that under both acidic and basic conditions the slow step in the cyclization reaction is formation of hydroxybenzimidazoline. Base catalysis is ascribed to proton abstraction from the amino group being concerted with the nucleophilic attack. The greater efficiency of acid catalysis (kH+/kOH− = 5000) is attributed to the ability of the amino group to act both as a proton trap
邻氨基乙酰苯胺的环化在广泛的条件下提供了一条通往
2-甲基苯并咪唑的途径。已经在pH范围-2-12·5范围内研究了反应动力学。为了比较,已经研究了两种异构的N-Me衍
生物,邻
氨基苯甲酰
苯胺和邻
氨基
三氟乙酰苯胺的环化。实验确定的伪一级速率常数根据以下表达式显示了酸和碱催化的影响:k = k o + k H + [H + ] /(1 + k c [H + ])+ kOH - [OH - ] + ķ HA [HA] + ķ甲[HA] + ķ甲- [A - ]结果表明,在酸性和碱性条件下环化反应缓慢步骤是形成hydroxybenzimidazoline的。碱催化归因于质子从与亲核攻击协同作用的
氨基中提取。酸催化的更高的效率(ķ ħ + / ķ OH -= 5000)归因于
氨基的能力既可以充当质子陷阱,又可以充当分子内一般酸。在
氨基和酰胺基都被质子化的强酸性条件下,
水解为
邻苯二胺非常重要。