The kinetics and mechanism of the cyclisation of some 2′-hydroxychalcones to flavanones in basic aqueous solution
作者:K. Barry Old、Lyndsay Main
DOI:10.1039/p29820001309
日期:——
profiles, one of which [chalcone (I)] differs from that previously reported. Possible effects on rate coefficients of non-bonded interactions between 6′-substituents and carbonyl oxygen are briefly considered but the differences between chalcones with and without 6′-substituents are sufficiently small to deter prolonged discussion. There seems to be little serious hindrance of cyclisation for any of the 6′-substituted
对于某些2'-羟基查耳酮,在其2'-羟基经过电离的pH范围(约8-11)中,查尔酮-黄酮平衡反应的速率系数已经确定。研究的查耳酮为母体2'-羟基查耳酮(I)及其以下衍生物:4'-OMe(II),6'-OMe(III),4'-OH(IV),4',6'-Me 2(V)和5',6'-苯并(VI)。伪一级速率系数(ķ OBS),其为有关可逆反应,是在正向和反向速率系数的总和,拟合动力学形式ķ OBS = KF甲+ ķ ' ˚F乙+ ķ “一OH –其中k和k '分别是中性和离子化查尔酮单分子环化的速率系数( f A和f B是在相关pH下以中性和离子化形式存在的总查尔酮的分数),其中k ”是黄烷酮涉及氢氧根离子(活性为OH –)的逆反应的二级速率系数。数据分析给出了速率系数和p K a除查耳酮(IV)以外的所有分子具有不同的动力学形式。提出了一种共轭添加消除机制来解释pH值速率分布,其中一种[查尔酮