A bicyclic ketone as a solid-state carbon-13 NMR intensity reference
摘要:
The synthesis and NMR relaxation properties of 4-(N-methylpyrrolidino)bicyclo[3.2.1]octan-8-one triflate (321) are described. The use of (CO)-C-13-enriched 321 as a C-13 intensity reference is justified and demonstrated. The dominant C-13 peak in 321-(CO)-C-13 is 217 ppm, far from most other C-13 chemical shifts of diamagnetlc organic compounds. Hence, this intensity reference peak avoids peak overlap problems for most organic compounds.
简单的二元羧酸:己二酸(1),琥珀酸(2)和丙二酸(3);制备了具有两个丙酸基团的更复杂的线性四吡咯:mesobiliverdin-XIIIα(4)和mesobilirubin-XIIIα(5),以及在C 10(6)具有宝石-二甲基的红宝石类似物,其99 C 13 CO 2 H基团。由水和H 2 O-(CD 3)2 SO溶液中的滴定曲线确定其p K a值:羧基碳13图C-NMR化学位移随p H的变化而变化。在H 2 O中具有已知p K a的二酸1-3的滴定曲线用作测定四吡咯二酸4-6的p K a s的校准标准:p K a1 = 3.9,对于4,p K a2 = 5.3 ;p K a1 = 4.2,p K a2 = 4.9(5),p K a1 = 4.7,p K a2 = 5.7H 2 O中的6。