Structural Determination of Grignard Reagents by Gas Electron Diffraction.

设计并制作了两个喷嘴。一种是使气态卤化物在镁表面发生反应，另一种是使气态镁与烷基卤化物发生反应。它们被用在装有质谱仪的气体电子衍射仪中。在这些喷嘴中加热甲基卤化物CH_3X (X=Cl， Br和I)，并用质谱仪分析反应产物。在所有情况下，只检测到烷基卤化物的热解产物，没有发现格氏试剂CH_3MgX的形成证据。因此，在气态甲基卤化物+固体镁或气态甲基卤化物+气态镁的体系中，均未发生镁与甲基卤化物的插入反应。这一结论与现有的基于从头计算的报告不一致，强烈表明溶剂化过程在格氏试剂的形成或稳定中起着重要作用。接下来，设计了一种新型喷嘴，将格氏试剂溶液引入电子衍射仪，并以小液滴的形式流出。当使用纯乙醚液体测试该喷嘴时，观察到样品的液滴在喷嘴端出现并快速蒸发。在这种条件下记录的衍射图样与气体样品的衍射图样相同。这意味着液滴样品完全汽化而没有形成团簇。最后，用格氏试剂CH_3I的乙醚溶液进行了类似的试验。然而，在这种情况下，发生了严重的白色物质沉积，可能是MgI_2和CH_3MgCH_3，这使得电子衍射实验无法进行。实验条件的修改正在等待中。

Two nozzles were designed and made. One was to make gaseous alkyl halides react on the magnesium surface and other one was to make reaction between gaseous magnesium and alkyl halides. They were used in a gas electron diffraction apparatus equipped with a mass spectrometer. Methyl halides, CH_3X (X=Cl, Br and I) , were heated in these nozzles and the reaction products were analyzed using the mass spectrometer. In all the cases, only the pyrolysis products of the alkyl halides were detected and no evidence was found for the formation of Grignard reagents, CH_3MgX.Therefore, it was concluded that in either system of gaseous methyl halide + solid magnesium or gaseous methyl halide + gaseous magnesium, no insertion reaction of magnesium into methyl halide occurs. This conclusion is not consistent with the existing reports based on ab initio calculations and it strongly suggests that the solvation process is playing an important role in formation or stabilization of Grignard reagents.In the next step, a new type of nozzle was designed, with which the solution of Grignard reagent is introduced into the electron diffraction apparatus and is effused as small droplets. When this nozzle was tested by using pure liquid of diethyl ether, the droplets of the sample was observed to be emerging and quickly evaporating at the nozzle end. The diffraction pattern recorded at this condition was found to be identical to that of the gaseous sample. This means that the droplet sample was completely vaporized without forming clusters.Finally, a similar test was carried out by using a diethyl ether solution of Grignard reagent, CH_3I.In this case, however, serious deposition of white substance that might be MgI_2 and CH_3MgCH_3 Happened, which made the electron diffraction experiment impossible. Revision of the experimental condition is pending.