Ermittlung der anisotropen brown'schen rotation monosubstituierter diphenyle in flüssiger phase durch 13CTfl-messungen

Advances in Molecular Relaxation Processes Pub Date : 1976-03-01 DOI:10.1016/0001-8716(76)80002-8

K.-L. Oehme, G. Rudakoff, R. Radeglia

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引用次数: 8

Abstract

Measurements of spin lattice ¹³C-relaxation times of protonated carbon atoms in monosubstituted diphenyls are described. It was possible to obtain the various T₁-times as a function of the anisotropic Brownian rotation by application of Woessner's theory. Two diffusion rates for the “overall” motion were derived from the T₁-values. It was ascertained that the anisotropy of rotation is fundamentally greater than the theoretical value, owing to the mass moments of inertia. This is caused by the very high “frictional effect” on the C_xy-rotation. The intramolecular rotation of the phenyl group was determined by two models of motion. The barrier of rotation was obtained from quadrupole T₁-data. These barriers are nearly the same as the values obtained using quantum-mechanics. The dependence of the barrier of rotation upon Hammett's σ_m-parameter is evident.

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通过13cc联盟测量，调查橄榄布朗圆顶分段n

描述了单取代二苯基中质子化碳原子自旋晶格13c弛豫时间的测量。应用Woessner的理论，可以得到各向异性布朗旋转的各种t1倍的函数。从t1值推导出“整体”运动的两个扩散速率。确定了由于质量惯性矩的影响，旋转的各向异性基本上大于理论值。这是由非常高的“摩擦效应”对xy旋转造成的。苯基的分子内旋转由两种运动模型决定。旋转势垒由四极杆t1数据获得。这些势垒与用量子力学得到的值几乎相同。旋转势垒对Hammett σm参数的依赖性是明显的。

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Advances in Molecular Relaxation Processes

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