CHEMICAL SHIFTS IN THE NUCLEAR MAGNETIC RESONANCE SPECTRA OF MOLECULES CONTAINING POLAR GROUPS
CHEMICAL SHIFTS IN THE NUCLEAR MAGNETIC RESONANCE SPECTRA OF MOLECULES CONTAINING POLAR GROUPS
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DOI：
10.1139/v60-040
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发表时间：
1960-01-01
期刊：
影响因子：
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通讯作者：
BUCKINGHAM, AD
中科院分区：
文献类型：
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作者：
BUCKINGHAM, AD
结果表明，分子其他部分的极性基团在特定核处产生的电场可以导致与场强的一次幂成比例的化学位移。当 X-H 键受到电场 E 时，其质子屏蔽常数的变化 Δσ 近似由下式给出： 其中 Ezi 是 E 在键方向上的分量。沿 X—H 键的场将原子核之间富集区域的电子吸引远离质子，从而导致其在较低磁场强度下发生共振，而沿 H—X 方向的场则导致在较高磁场强度下发生共振。相邻溶剂分子的极化产生的电场也可能很重要，并导致与溶剂的介电常数相关的溶剂位移。当分子是刚性的时，可以轻松估计内部场的方向以及由溶剂引起的方向，因此该模型可用于分配光谱。它简单而准确地描述了取代苯的观察光谱以及一些溶剂对顺式和反式 1,2-二氯乙烯质子共振的影响。
It is shown that the electric field at a particular nucleus arising from polar groups in other parts of a molecule can lead to chemical shifts proportional to the first power of the field strength. The change Δσ in the proton screening constant of an X—H bond when it is subjected to an electric fieldEis approximately given bywhereEzis the component ofEin the bond direction. A field along the X—H bond draws the electrons in the enriched region between the nuclei away from the proton, thereby causing its resonance to occur at lower magnetic field strengths, while a field in the H—X direction leads to resonance at higher fields. The electric field produced by the polarization of neighboring solvent molecules may also be important and lead to a solvent shift related to the dielectric constant of the solvent. The direction of the internal field, and that due to the solvent, can easily be estimated when the molecule is rigid, so that the model can be useful in assigning spectra. It gives a simple and reasonably accurate account of the observed spectra of substituted benzenes and of some solvent effects on the proton resonances ofcis- andtrans-1,2-dichloroethene.