The Pyrolysis of Azides in the Gas Phase
The Pyrolysis of Azides in the Gas Phase
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DOI：
10.1002/anie.198705041
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发表时间：
1987-06
影响因子：
--
通讯作者：
H. Bock;R. Dammel
中科院分区：
文献类型：
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作者：
H. Bock;R. Dammel
近年来，非金属元素化学经历了一个快速发展的时期，通常被称为“文艺复兴”。这里只强调其中一个关键方面：人们发现了许多短寿命的分子，这些分子含有与第三周期和更高周期的元素的多个键，通常伴随着衍生物的计划合成，这些衍生物在空间上被庞大的基团屏蔽，从而在动力学上稳定。因此，今天的分子，如硅杂苯H6 C6 −nSin和硅乙烯H2SiCH 2或R2 SiCR 2，二硅烯R2 SiSiR 2和二膦RPPR，硅苯基异腈H5 C6 NSi或亚甲基膦RCP，都是众所周知的物种。具有P6环或硅中心的三明治化合物表明，现在几乎没有任何障碍阻碍非金属化学家的想象力。与此形成鲜明对比的是，我们对化学反应的“微观”途径缺乏了解：因此，除了例如由分子束实验提供的信息，或者来自涉及仅由几个原子组成的物质的精确数值计算之外，中等大小的分子必须从哪个方向彼此接近以成功地碰撞并形成“反应复合物”在很大程度上仍然是未知的，- 叠氮化物XN 3的热解，叠氮化物XN 3即在冷凝相中点燃时倾向于剧烈爆炸但可以在低压气流系统中加热而没有太大风险的化合物，说明了活性中间体的研究是令人感兴趣的，不仅因为新的分子可能被发现和分离，从而扩大了合成的可能性。此外，这些叠氮化物热解的“微观”途径的某些方面可以令人满意地描述计算的能量超曲面的基础上，和分子动力学的影响变得实验可见的“化学活化”的中间体，导致他们的“热爆炸”。
The chemistry of the non-metallic elements has in recent years passed through a period of rapid development, often referred to as its “renaissance”. To emphasize just one of the key facets: numerous short-lived molecules containing multiple bonds to elements of the third and higher periods have been discovered, often accompanied by the planned synthesis of derivatives which are sterically shielded by bulky groups and thus kinetically stabilized. Thus today molecules such as silabenzenes H6C6−nSin and silaethenes H2SiCH2 or R2SiCR2, disilenes R2SiSiR2 and diphosphenes RPPR, silaphenylisonitrile H5C6NSi, or methylidyne-phosphanes RCP, are all well-known species. Sandwich compounds with P6 rings or silicon centers demonstrate that there are now hardly any barriers to impede the imagination of the non-metal chemist. In sharp contrast is our lack of knowledge regarding the “microscopic” pathways of chemical reactions: thus apart from information provided for example by molecular beam experiments, or from exact numerical calculations involving species consisting of only a few atoms, it remains largely unknown from which directions medium-sized molecules must approach each other to successfully collide and form a “reaction complex”, in which way their structures are changed in such a process or which role is played by molecular dynamics in the energy transfer.–The pyrolysis of azides XN3, i.e. compounds which tend to explode violently when ignited in the condensed phase but can be heated in low-pressure gas flow systems without much risk, illustrates that studies of reactive intermediates are of interest not only because novel molecules may be discovered and isolated, and thereby possibilities for synthesis expanded. Moreover, some aspects of the “microscopic” pathways of these azide pyrolyses can be described satisfactorily on the basis of calculated energy hypersurfaces, and the influence of molecular dynamics becomes experimentally visible in the “chemical activation” of intermediates which leads to their “thermal explosion”.