Constantinidis P, Hirsch F, Fischer I, Dey A, Rijs A M
Institute of Physical and Theoretical Chemistry, University of Würzburg , Am Hubland, D-97074 Würzburg, Germany.
Radboud University , Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands.
J Phys Chem A. 2017 Jan 12;121(1):181-191. doi: 10.1021/acs.jpca.6b08750. Epub 2016 Dec 20.
The propargyl radical is considered to be of key importance in the formation of the first aromatic ring in combustion processes. Here we study the bimolecular (self-) reactions of propargyl in a high-temperature pyrolysis flow reactor. The aromatic reaction products are identified by IR/UV ion dip spectroscopy, using the free electron laser FELIX as mid-infrared source. This technique combines mass selectivity with structural sensitivity. We identified several aromatic reaction products based on their infrared spectra, among them benzene, naphthalene, phenanthrene, indene, biphenyl, and surprisingly a number of aromatic compounds with acetylenic (ethynyl) side chains. The observation of benzene confirms that propargyl is involved in the formation of the first aromatic ring. The observation of compounds with acetylenic side chains shows that, in addition to a propargyl- and phenyl-based mechanism, the HACA (hydrogen abstraction CH addition) mechanism of polycyclic aromatic hydrocarbons formation is present, although no acetylene was used as a reactant. On the basis of the experimental results we suggest a mechanism that connects the two pathways.
炔丙基自由基被认为在燃烧过程中首个芳香环的形成中起着关键作用。在此，我们研究了炔丙基在高温热解流动反应器中的双分子（自）反应。利用自由电子激光FELIX作为中红外光源，通过红外/紫外离子偶极光谱法鉴定芳香族反应产物。该技术将质量选择性与结构敏感性相结合。我们根据红外光谱鉴定了几种芳香族反应产物，其中包括苯、萘、菲、茚、联苯，令人惊讶的是还有一些带有乙炔基（乙炔基）侧链的芳香族化合物。苯的观测结果证实炔丙基参与了首个芳香环的形成。带有乙炔基侧链的化合物的观测结果表明，除了基于炔丙基和苯基的机理外，多环芳烃形成的HACA（氢提取CH加成）机理也存在，尽管未使用乙炔作为反应物。基于实验结果，我们提出了一种将这两种途径联系起来的机理。
