Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
J Chem Phys. 2011 Jul 7;135(1):014306. doi: 10.1063/1.3604005.
We have used a heated 2 cm × 1 mm SiC microtubular (μtubular) reactor to decompose acetaldehyde: CH(3)CHO + Δ → products. Thermal decomposition is followed at pressures of 75-150 Torr and at temperatures up to 1675 K, conditions that correspond to residence times of roughly 50-100 μs in the μtubular reactor. The acetaldehyde decomposition products are identified by two independent techniques: vacuum ultraviolet photoionization mass spectroscopy (PIMS) and infrared (IR) absorption spectroscopy after isolation in a cryogenic matrix. Besides CH(3)CHO, we have studied three isotopologues, CH(3)CDO, CD(3)CHO, and CD(3)CDO. We have identified the thermal decomposition products CH(3) (PIMS), CO (IR, PIMS), H (PIMS), H(2) (PIMS), CH(2)CO (IR, PIMS), CH(2)=CHOH (IR, PIMS), H(2)O (IR, PIMS), and HC≡CH (IR, PIMS). Plausible evidence has been found to support the idea that there are at least three different thermal decomposition pathways for CH(3)CHO; namely, radical decomposition: CH(3)CHO + Δ → CH(3) + [HCO] → CH(3) + H + CO; elimination: CH(3)CHO + Δ → H(2) + CH(2)=C=O; isomerization∕elimination: CH(3)CHO + Δ → [CH(2)=CH-OH] → HC≡CH + H(2)O. An interesting result is that both PIMS and IR spectroscopy show compelling evidence for the participation of vinylidene, CH(2)=C:, as an intermediate in the decomposition of vinyl alcohol: CH(2)=CH-OH + Δ → [CH(2)=C:] + H(2)O → HC≡CH + H(2)O.
我们使用加热的 2 厘米×1 毫米碳化硅微管式（μ 管式）反应器来分解乙醛：CH(3)CHO + Δ → 产物。在 75-150 托和高达 1675 K 的温度下进行热分解，这些条件对应于在 μ 管式反应器中的停留时间约为 50-100 μs。通过两种独立的技术鉴定乙醛分解产物：真空紫外光电离质谱（PIMS）和红外（IR）吸收光谱，在低温基质中分离后。除了 CH(3)CHO，我们还研究了三种同位素，CH(3)CDO、CD(3)CHO 和 CD(3)CDO。我们已经鉴定出热分解产物 CH(3)（PIMS）、CO（IR、PIMS）、H（PIMS）、H(2)（PIMS）、CH(2)CO（IR、PIMS）、CH(2)=CHOH（IR、PIMS）、H(2)O（IR、PIMS）和 HC≡CH（IR、PIMS）。已经找到了合理的证据支持这样一种观点，即 CH(3)CHO 至少有三种不同的热分解途径；即自由基分解：CH(3)CHO + Δ → CH(3) + [HCO] → CH(3) + H + CO；消除：CH(3)CHO + Δ → H(2) + CH(2)=C=O；异构化/消除：CH(3)CHO + Δ → [CH(2)=CH-OH] → HC≡CH + H(2)O。一个有趣的结果是，PIMS 和 IR 光谱都有力地证明了乙烯基，CH(2)=C:，作为分解乙烯醇的中间产物的参与：CH(2)=CH-OH + Δ → [CH(2)=C:] + H(2)O → HC≡CH + H(2)O。
