O'Keeffe Patrick, Scotti Giorgio, Stranges Domenico, Rodrigues Paula, Barros M Teresa, Costa Maria L
Dipartimento di Chimica, Università La Sapienza, P.le A. Moro 5, Rome I-00185, Italy.
J Phys Chem A. 2008 Apr 10;112(14):3086-93. doi: 10.1021/jp077406j. Epub 2008 Mar 15.
The thermal decomposition of azidoacetone (CH3COCH2N3) was studied using a combined experimental and computational approach. Flash pyrolysis at a range of temperatures (296-1250 K) was used to induce thermal decomposition, and the resulting products were expanded into a molecular beam and subsequently analyzed using electron bombardment ionization coupled to a quadrupole mass spectrometer. The advantages of this technique are that the parent molecules spend a very short time in the pyrolysis zone (20-30 mus) and that the subsequent expansion permits the stabilization of thermal products that are not observable using conventional pyrolysis methods. A detailed analysis of the mass spectra as a function of pyrolysis temperature revealed the participation of five thermal decomposition channels. Ab initio calculations on the stable structures and transition states of the azidoacetone system in combination with an analysis of the dissociative ionization pattern of each channel allowed the identity and mechanism of each channel to be elucidated. At low temperatures (296-800 K) the azide decomposes principally by the loss of N2 to yield the imine (CH3COCHNH), which can further decompose to CH3CO and CHNH. At low and intermediate temperatures a process involving the loss of N2 to yield CH3CHO and HCN is also open. Finally, at high temperatures (800-1250 K) a channel in which the azide decomposes to a stable cyclic amine (CO(CH2)2NH) (after loss of N2) is active. The last channel involves subsequent thermal decomposition of this cyclic amine to ketene (H2CCO) and methanimine (H2CNH).
采用实验与计算相结合的方法研究了叠氮丙酮（CH3COCH2N3）的热分解。在一系列温度（296 - 1250 K）下进行快速热解以引发热分解，生成的产物被扩展到分子束中，随后使用与四极杆质谱仪耦合的电子轰击电离进行分析。该技术的优点是母体分子在热解区停留的时间非常短（20 - 30微秒），并且随后的膨胀使得使用传统热解方法无法观察到的热产物得以稳定。对作为热解温度函数的质谱进行详细分析，揭示了五个热分解通道的参与情况。对叠氮丙酮系统的稳定结构和过渡态进行从头算计算，并结合对每个通道的解离电离模式的分析，得以阐明每个通道的特性和机理。在低温（296 - 800 K）下，叠氮化物主要通过失去N2分解生成亚胺（CH3COCHNH），亚胺可进一步分解为CH3CO和CHNH。在低温和中温下，一个涉及失去N2生成CH3CHO和HCN的过程也会发生。最后，在高温（800 - 1250 K）下，一个通道（叠氮化物在失去N2后分解为稳定的环状胺（CO(CH2)2NH））是活跃的。最后一个通道涉及该环状胺随后热分解为乙烯酮（H2CCO）和甲亚胺（H2CNH）。
