We observed that the product of a Buchwald–Hartwig coupling reaction extracted from the organic phase easily, relative to the starting aryl bromide as the pH was lowered. This was surprising given the similarity of their pK_a's. The product’s extraction curve was also significantly steeper than expected. A consideration of the relevant equilibria, including all three of the product’s pK_a's, led to a general model for the liquid–liquid extraction behavior of ionizable molecules. This model predicts the observed, useful extraction behavior.

中文翻译：

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一个通用的液-液分配方程及其后果：从pH依赖性药物中间体的提取中学习

我们观察到，随着pH降低，相对于起始的芳基溴化物，布赫瓦尔德-哈特维格偶联反应的产物易于从有机相中提取。考虑到他们的p K _a的相似性，这令人惊讶。产品的提取曲线也比预期的要陡得多。考虑到相关平衡，包括所有三个产品的p K _a，得出了可电离分子的液-液萃取行为的通用模型。该模型可预测观察到的有用的提取行为。