Mechanistic Investigation of the Oxidative Cleavage of the Carbon-Carbon Double Bond in α,β-Unsaturated Compounds by Hexachloroiridate(IV) in Acetate Buffer
作者:Biswajit Pal
DOI:10.1002/kin.20824
日期:2014.1
The hexachloroiridate(IV) oxidation of α,β‐unsaturated compounds such as acrylic acid, acrylamide, and acrylonitrile (CH2=CHX; X = –COOH, –CONH2, and –CN) was carried out in NaOAc‐AcOH buffer medium. The reaction follows complex kinetics, being first order in [IrIV] and complex order in [CH2=CHX]. H+ ion has no effect on the reaction rate in the pH range 3.42–4.63. The pseudo–first‐order rate constant
α,β-不饱和化合物(如丙烯酸,丙烯酰胺和丙烯腈(CH 2 = CHX; X = –COOH,–CONH 2和–CN))的六氯铱酸盐(IV)氧化反应在NaOAc-AcOH缓冲液中进行。反应遵循复杂的动力学,在[Ir IV ]中为一级,在[CH 2 = CHX]中为复杂级。高+离子在pH范围3.42–4.63中对反应速率没有影响。伪一级速率常数随着介电常数的减小和介质的离子强度的减小而减小。氧化速率遵循以下顺序:丙烯腈>丙烯酰胺>丙烯酸。提出了一种机制,涉及在底物和氧化剂之间形成不稳定的中间体配合物,该中间体配合物在缓慢的速率确定步骤中伴随着Ir(IV)还原为Ir(III)转化为自由基阳离子。自由基阳离子随后分解为醛,该醛作为碳-碳双键裂解的最终产物出现。氧化的主要产物被1鉴定为HCHO1 H NMR。评估了慢速确定步骤的激活参数和与拟议机制的平衡步骤相关的热力学参数。活化的焓与活化的熵成线