Pyrolysis Of Azides Research Articles

Pyrolysis of Aryl Azides. IX. Azomethines as Weak Neighboring Groups

The following rates of pyrolysis (relative to azidobenzene at 120°) have been measured in decalin solution: 2-azidobenzaldehyde, 28.8; 2-azidobenzylideneaniline, 59.5; 2-azidobenzaldehyde phenylhydrazone, 8.9; 2-azidobenzaldehyde oxime O-methyl ether, 1.3;2-azidoacetophenone oxime O-methyl ether, 23.4; 2-azidobenzophenone phenylhydrazone, 9.7. It is argued that these relative rates are largely determined by the extent to which the ortho substituent is in the reactive conformation for an electrocyclic process. Indazoles substituted on N2 are isolated from pyrolysis of those azides with ortho-azomethine substituents.

The Pyrolysis of Azides in the Gas Phase

AbstractThe 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 H2SiCH2 or R2SiCR2, disilenes R2SiSiR2 and diphosphenes RPPR, silaphenylisonitrile H5C6NSi, or methylidyne‐phosphanes RCP, 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 XN3, 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”.