Structural Determination of Grignard Reagents by Gas Electron Diffraction.

设计并制造了两个喷嘴。一种是使气态的烷基卤化物在镁表面发生反应，另一种是气态的镁与烷基卤化物发生反应。它们被用于配有质谱仪的气体电子衍射仪中。在这些喷嘴中加热甲烷卤化物CH3X(X=氯、溴和碘)，并用质谱仪对反应产物进行分析。结果表明，无论是在气态甲基卤化物+固体镁还是气态甲基卤化物+气态镁体系中，均未发生镁的插入反应。这一结论与现有的基于从头计算的报道不一致，它强烈地表明溶剂化过程在格氏试剂的形成或稳定中起着重要的作用。在下一步，设计了一种新型的喷嘴，将格氏试剂的溶液引入电子衍射仪并以小液滴的形式流出。用乙醚纯液对该喷嘴进行测试时，观察到样品在喷嘴端部出现液滴并迅速蒸发。在此条件下记录的衍射图与气态样品的衍射图相同。这意味着液滴样品完全汽化了，没有形成团簇。最后，用格氏试剂CH31的乙醚溶液进行了类似的测试，但在这种情况下，白色物质严重沉积，可能是MgI_2和CH_3MgCH_3，这使得电子衍射实验无法进行。对实验条件的修改正在进行中。

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.