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有关阳离子水化作用的核磁共振研究,由于通常的实验方法不易做到(M)/(H_2O)>1的条件,所以观察不到少量水分子在大量阳离子环境中水合情况,所得到水中质子化学位移的变化很小,一般仅有0.1 ppm。本文利用无水皂化萃取剂加水生成微乳状液的方法,可使(M~+)/(H_2O)从100:1到1:100范围内变化。在加入不同量水的过程中,水的~1H化学位移出现两个极限值:在(M~+)/(H_2O)=100/1附近,配位水的化学位移向低场移动有最大极限值,在含水量增高的情况,逐渐趋近缔合水(即正常液体水)的化学位移4.8 ppm。这一过程可以看到配位水的化学位移比缔合水向低场移动2 ppm以上,比通常在浓盐水溶液中观察到的差值提高了一个数量级。因而为研究离子水化过程提供了一个新途径。 当(M)/(H_2O)大于100/时,配位水的化学位移随阳离子不同而趋于不同极限值,其顺序为:NH_4~+(7.54)>Li~+(7.08)>Na~+(6.22)>K~+(6.00)。这是由于阳离子场不同,其水化作用也不同。
For the study of cation hydration in nuclear magnetic resonance, a small amount of water molecules can not be observed to hydrate in a large amount of cationic environment due to the difficulty of (M) / (H 2 O)> 1 in conventional experimental methods. The obtained proton chemistry The change in displacement is small, typically only 0.1 ppm. In this paper, the method of adding water to form microemulsion by anhydrous saponification extractant can change (M ~ +) / (H_2O) from 100: 1 to 1: 100. In the process of adding different amount of water, the chemical shift of water shows two limit values: the chemical shift of coordinated water has a maximum limit to the low field near (M ~ +) / (H_2O) = 100/1 In the case of increasing water content, the chemical shift of associated water (ie, normal liquid water) gradually approaches 4.8 ppm. This process shows that the chemical shift of coordination water moves more than 2 ppm lower than that of associated water, an order of magnitude more than the difference observed in normally brine solutions. So it provides a new way to study the ion hydration process. When the molar ratio of (M) / (H 2 O) is greater than 100 /, the chemical shifts of coordinated water tend to different limits with different cations, and the order is: NH 4 + 7.55 Li + 7.08 Na + (6.22)> K ~ + (6.00). This is due to the different cation field, its hydration is also different.