Carbon‐13 NMR relaxation studies of some dicyclohexyl compounds
Carbon‐13 NMR relaxation studies of some dicyclohexyl compounds
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一些二环己基化合物的碳 13 NMR 弛豫研究
DOI：
10.1002/mrc.1260290807
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
L. Sutcliffe
中科院分区：
文献类型：
--
作者：
D. Gillies;Stephen J. Matthews;L. Sutcliffe
研究了四种二环己基化合物，其中一种是牵引流体，其余的具有相关的结构，其中环己烷环被两个或三个碳原子分开。在22.50和100.62 MHz下在宽温度范围内获得了四种化合物的碳-13 NMR T1和NOE数据。同时将数据拟合到约化的洛伦兹谱密度或"无模型"的双相关时间谱密度。这是第一次有可能观察到从完整的"无模型"两相关时间谱密度到约化洛伦兹谱密度的跟踪。从这些拟合得到的相关时间和活化能可以得出结论，所有化合物都具有半刚性结构。的结构和分子力学计算的旋转障碍的计算机建模给出的结果与那些从NMR数据。类似地，发现化合物的摩擦系数与NMR和分子力学结论相关，即通过将甲基引入环己烷环之间的连接中产生的增加的刚性导致更有效的牵引流体。因此，在实验室中设计新的牵引液似乎是可行的。
Four dicyclohexyl compounds were studied, one of which is a traction fluid and the remainder have related structures in which the cyclohexane rings are separated by two or three carbon atoms. Carbon‐13 NMR T1 and NOE data were obtained for the four compounds at 22.50 and 100.62 MHz over a wide temperature range. The data were fitted simultaneously to either a reduced Lorentzian spectral density or to a ‘model‐free’ two‐correlation time spectral density. For the first time it has been possible to observe the tracking from the full ‘model‐free’ two‐correlation time spectral density to the reduced Lorentzian spectral density. From the correlation times and activation energies derived from these fittings, it can be concluded that all the compounds have semi‐rigid structures. Computer modelling of the structures and molecular mechanics calculations of the rotational barriers gave results in agreement with those from the NMR data. Similarly, it was found that the friction coefficients of the compounds correlate with the NMR and molecular mechanics conclusions, namely that the increased rigidity produced by the introduction of methyl groups into the linkage between the cyclohexane rings leads to a more effective traction fluids. Hence it seems to be feasible to design new traction fluids in the laboratory.