sslin
第2楼2009/02/17
很有意思的问题, 值得试验看看.
理论上 H-D 之间存在耦合, 两者的旋转量子数分别为 1/2 与1. 氘对氢谱以及碳谱的裂分为众所周知. H 对氘谱应该也会产生耦合效果.
我们以前曾多次检测氘谱, 倒是没有留意到 H 对 D 的裂分影响. 或许是我们检测这些杂核时 (我们平时将 D 也定义成杂核), 都没有注意到进行匀场, 或许因此导致无法观察到精细裂分结构.
由于检测氘谱时, 需要将 lock cable 拆除掉 (所有杂核检测中比较特殊的作法, 因为谱仪设计是锁定氘核), 否则信号太强无法检测. 拆除 lock calbe 则无法锁场, 也因此就没有考虑到匀场操作. 下次检测可以考虑尝试看看能否观察到裂分情况.
另外一种尝试, 不使用富集太强的氘代样品, 或许可以考虑稀释浓度, 进行锁场/匀场, 观察情况.
celan
第5楼2009/02/18
网络资料
2Deuterium NMR
2Deuterium (heavy hydrogen) NMR is usually used for field frequency lock. At natural abundance it has very low sensitivity but when enriched it is of medium sensitivity. Deuterium usually yields broad signals whose line width typically varies between a few hertz and a few kilohertz. The spectrum has the same narrow chemical shift range as for 1H but its low resolution and lower sensitivity make it a poor alternative. Deuterium-deuterium couplings are about 40 times smaller that proton-proton couplings and are therefore not observed. However, in partially deuterated molecules small proton-deuterium couplings can be observed. The main use of deuterium spectra is for determining the effectiveness of chemical deuteration.
1H and 2D-NMR spectra of Amphetamine sulfate–d3 showing successful specific deuteration of the methyl图谱见附件