COMPARISON OF DEUTERIUM & TRITIUM ISOTOPE EFFECTS ON CHEMICAL SHIFTS

氘的比较

• 批准号: 6220452
• 负责人: DAVID E WEMMER
• 金额: $ 1.21万
• 依托单位: UNIVERSITY OF CALIF-LAWRENC BERKELEY LAB
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6220452
• 关键词: biological products; biomedical resource

NMR chemical shifts are very sensitive probes for changes in the local environment around the nuclei being detected. In particular there are substantial isotope effects on chemical shifts, both primary (being detected on the atom whose mass is changing) and secondary (being detected on other nuclei near that with altered mass). The isotopes of hydrogen provide large relative mass changes, and have been used fairly extensively to investigate hydrogen bonding. Both primary and secondary shifts can be quite substantial, propagating many bonds from the site of hydrogen bond formation. A majority of studies have been done comparing chemical shifts with compounds containing protons vs. deuterium. The deuterium lines are somewhat broader than proton due to quadrupole coupling, and the magnetic moment is 1/6th that of a proton, limiting the accuracy of the shift measurements. We have now undertaken a study to extend measurements to tritium. The main motivation is to compare the isotope shifts of deuterium and tritium relative to proton and see whether the induced effect scales with mass difference in the same way that the proton - deuterium shift scales. Deviations from this behavior could reflect asymmetry in the hydrogen bond potential, and could help understanding of strong hydrogen bonds. A wide variety of organic compounds were studied dissolved in organic solvents which contained intramolecular hydrogen bonds. The donors and acceptors were varied over a wide range of chemical functionalities, including O, N and S on both donor and acceptor ends. Substitution of tritium for protons was accomplished through addition of small amounts of water. The spin 1/2 character of tritium made possible much more accurate determinations of shifts than with deuterium. Only very small deviations from the expected H-D / H-T ratios of 1.4 were observed; for most compounds the value was at the expected theoretical value.

NMR化学位移是非常敏感的探针， 被检测的原子核周围的局部环境。 特别是 在化学位移上存在大量的同位素效应， （在质量变化的原子上检测到）和次级 （在质量改变的核附近的其他核上被检测到）。 的 氢的同位素提供大的相对质量变化，并且具有 被广泛用于研究氢键。 两 初级和次级转变可能相当大，并不断传播 许多键从氢键形成的位置。 大多数 研究已经完成比较化学位移与化合物 含有质子和氘。 氘线有点 由于四极耦合，比质子更宽， 磁矩是质子的六分之一，限制了位移的准确性 测量. 我们现在进行了一项研究， 到氚。 主要动机是比较 氘和氚相对于质子，看看是否诱导 效应与质量差成比例，就像质子- 氘位移标度 这种行为的偏差可能反映出 氢键势的不对称性，可以帮助理解 强氢键。 各种各样的有机化合物， 研究溶解在有机溶剂中的分子内 氢键 供体和受体在宽范围内变化 一系列化学官能团，包括两个供体上的O、N和S 和受体末端。 用氚取代质子， 通过添加少量的水来完成。 旋转1/2 氚的特性使得更精确的测定成为可能 比氘更容易发生变化。 只有非常小的偏差， 观察到预期的H-D / H-T比为1.4;对于大多数化合物， 值为预期理论值。