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用~(23)Na NMR研究了15-冠-5(15C5),2,3-苯并-15-冠-5(B-15C5),2,3-苯并-6-甲基-15冠-5(BC1-15C5),2,3-苯并-8,12-二甲基-15-冠-5(BC2-15C5)在丙酮中与Na~+的配位反应,由此探索甲基的影响。实验结果表明,当在金属盐溶液中加入冠醚,配体为15C5时,体系表观化学位移移至低场,配体为B-15C5,BC1-15C5,BC2-15C5时,体系的表现化学位移移至高场。后者与苯并-18-冠-6及其甲基衍生物不同,这是由于苯环在空间排布不同所致,用Newton-Raphson法和描坑法(Pit-mapping)拟合实验数据,发现BC1-15C5和BC2-15C5除形成NaL~+和NaL_2~+外还有不稳定的Na_3L_2~(3+)形成。本文对形成过程和生成NaL~+反应的平衡常数lgK_(11)与甲基数的关系亦作了讨论,lgK_(11)与甲基数目n近似成直线关系,可用下式表示:lgK_(11)=3.50-0.480n,n=0,1,2。
The 15-crown-5 (15C5), 2,3-benzo-15-crown-5 (B-15C5) -5 (BC1-15C5) and 2,3-benzo-8,12-dimethyl-15-crown-5 (BC2-15C5) Impact. The experimental results show that when the crown ether is added to the metal salt solution and the ligand is 15C5, the apparent chemical shift of the system shifts to a low field. When the ligand is B-15C5, BC1-15C5, BC2-15C5, Displacement moves to high field. The latter is different from benzo-18-crown-6 and its methyl derivatives due to the spatial distribution of benzene rings. The experimental data were fitted by Newton-Raphson method and Pit-mapping It was found that BC1-15C5 and BC2-15C5 also formed unstable Na_3L_2 ~ (3+) in addition to the formation of NaL ~ + and NaL_2 ~ +. The relationship between the formation equilibrium constant lgK_ (11) and the number of methyl groups in the NaL ~ + reaction is also discussed. The linear relationship between lgK_ (11) and the number of methyl groups n can be expressed as follows: lgK_ (11) ) = 3.50-0.480 n, n = 0,1,2.