Stella V J, Gish R
J Pharm Sci. 1979 Aug;68(8):1042-7. doi: 10.1002/jps.2600680832.
The ionization kinetics of carbon acids are slow relative to those of classical acids and bases. Phenindione (2-phenyl-1,3-indandione) is a 1,3-diketone carbon acid of macroscopic experimental pKa 4.09 at 25 degrees and ionic strength 0.1. The ionization kinetics of phenindione were determined at an ionic strength of 0.1 and 25 degrees using stopped-flow spectrophotometry and a pH jump technique. A log k'obs-pH profile for the approach to the ionization equilibrium was determined, and a mechanism consistent with the profile was postulated. The percent enol versus diketo form of phenindione and the pKaenol and pKadiketo were calculated from the kinetic data. Phenindione acid deprotonation kinetics by various oxygen and nitrogen bases suggested that, with bases of pKa 4.7--8.5 and in the pH 5--8.5 range, the acidic phenindione proton as approximately 45% transferred in the rate-determining transition state.
相对于经典酸碱而言，碳酸的电离动力学较为缓慢。苯茚二酮（2-苯基-1,3-茚二酮）是一种1,3-二酮碳酸，在25℃和离子强度0.1时，其宏观实验测得的pKa为4.09。采用停流分光光度法和pH跃变技术，在离子强度0.1和25℃条件下测定了苯茚二酮的电离动力学。测定了达到电离平衡过程的log k'obs-pH曲线，并推测了与该曲线相符的机理。根据动力学数据计算了苯茚二酮烯醇式与二酮式的比例以及pKaenol和pKadiketo。各种氧碱和氮碱对苯茚二酮酸的去质子化动力学表明，对于pKa为4.7 - 8.5的碱且在pH 5 - 8.5范围内，酸性苯茚二酮质子在速率决定过渡态中约有45%发生转移。
