Synthesis and acidity constants of 13CO2H-labelled mono and dipyrrole carboxylic acids. pKa from 13C-NMR
作者:Darren L. Holmes、David A. Lightner
DOI:10.1016/0040-4020(94)01052-2
日期:1995.2
[1-13C]-phenylacetic (2) acids were determined to be 4.60 and 4.16 respectively in H2O, and 4.67 and 4.31 respectively in H2O-27% vol (CD3)2SO. Bilirubin analogs, xanthobilirubic acid (5) and nor-xanthobilirubic acid (6) were determined to have pKa values of 4.76 and 4.64 respectively in H2O-27% vol (CD3)2SO, and extrapolated to pKa values ∼4.62 and 4.51 in H2O.
制备了六种在CO 2 H基团中高度富集13 C的单羧酸,并在H 2 O和H 2 O-(CD 3)2中以低浓度10 -4 -10 -5 M的pK a值进行了测定。通过分析pH依赖性13 CO 2 H NMR化学位移分析SO混合物。CO的变化的曲线图2 H(CO 2 - )13 C-NMR化学位移VS pH值,得到一个典型的滴定曲线从其中的pK一个的对[1- 13C] -phenylpropionic(1)和[1- 13 C] -phenylacetic(2测定)的酸为4.60和H中分别4.16 2 O,和4.67和4.31分别H中2 -O-27%(体积)(CD 3)2 SO。经测定,在H 2 O-27%vol(CD 3)2 SO中,胆红素类似物,黄胆红酸(5)和去黄胆红酸(6)的pK a值分别为4.76和4.64 ,并推断为pK a值〜 H 2 O中为4.62和4.51 。