新型19F pH指示剂：氟苯胺类。
New class of 19F pH indicators: fluoroanilines.
作者信息
Deutsch C J, Taylor J S
机构信息
Department of Physiology, University of Pennsylvania, Philadelphia 19104.
出版信息
Biophys J. 1989 Apr;55(4):799-804. doi: 10.1016/S0006-3495(89)82879-6.
The pH dependence of the 19F chemical shift has been characterized for a number of fluorine-substituted aniline derivatives. These compounds constitute a new class of 19F nuclear magnetic resonance (NMR) pH indicators, characterized by single 19F resonance lines with sensitivities ranging from 2 to 7 ppm/pH unit near the aniline pKa; total shifts between conjugate acid and base of 5-15 ppm; and pKas ranging from 1 to 7. One compound, N,N-(methyl-2-carboxyisopropyl)-4-fluoroaniline, has a pKa of 6.8 and a sensitivity of 5 ppm/pH unit. This compound displays significant broadening of its 19F resonance near the aniline pKa (6.8), due to a decreased rate of exchange between conjugate acid and base species. Our results are consistent with slow dissociation of an intramolecular hydrogen bond in the zwitterionic species that limits the exchange rate between protonated and unprotonated forms for N,N-(methyl-2-carboxyisopropyl)-4-fluoroaniline.
对于多种氟取代苯胺衍生物，已对其¹⁹F化学位移的pH依赖性进行了表征。这些化合物构成了一类新型的¹⁹F核磁共振（NMR）pH指示剂，其特征在于具有单一的¹⁹F共振线，在苯胺pKa附近的灵敏度范围为2至7 ppm/pH单位；共轭酸和碱之间的总位移为5 - 15 ppm；pKa范围为1至7。一种化合物N,N -（甲基 - 2 - 羧基异丙基）- 4 - 氟苯胺，其pKa为6.8，灵敏度为5 ppm/pH单位。由于共轭酸和碱物种之间的交换速率降低，该化合物在苯胺pKa（6.8）附近其¹⁹F共振出现明显展宽。我们的结果与两性离子物种中分子内氢键的缓慢解离一致，这限制了N,N -（甲基 - 2 - 羧基异丙基）- 4 - 氟苯胺质子化和非质子化形式之间的交换速率。
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