Manufacture of Low-temperature NMR insert abd probe: Stereodynamics of Pyrrolidine derivatives

点击翻译按钮获取中文摘要

Outline of the purpose of this investigation(1) To observe, by means of a combination of dynamic nmr(dnmr) and molecular mechanics(MM) calculations, the rate processes with a relatively low energy barrier involved in a variety of piperidines and pyrrolidines and to determine the thermodynamic parameters of the processes.(2) To modify the probe, and the low-temperature accessories, such as inserts or nitrogen gas generator, of the nmr instrument (FX-90Q) so that the temperature of -150゜C will be obtained. Such a low temperature is essential to accomplish the above mentioned purpose, since the energy processes to be observed are of low barrier such as the inversion of nitrogen or the restricted rotation of longer bonds such as Ge-C.(3) To determine the thermodynamic parameters of 1-aza-8-heterabicyclo[4.3.0]nonanes and germacyclohexanes. The barriers to be observed are of the order of five kcal/ <mol^(-1)> .Outline of the results(1) The modification of instrument enables us to attain -140゜C without difficulty. To attain -150゜C was found difficult. (2) The inversion of deutrated 1-aza-8-heterabicyclo[4.3.0]nonanes as nearly complete, but the temperature was insufficient to observe a genuine freezing. Similarly, no freezing was observed at this temperature for the ring reversal of germacyclohexanes.