Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, La Jolla, California 92093-0340, United States.
J Phys Chem A. 2013 Nov 21;117(46):12035-41. doi: 10.1021/jp404343w. Epub 2013 Aug 7.
The ethoxy radical is an important species in combustion chemistry; however, considerable debate regarding the fragmentation pathways exists. In order to examine the stability and dissociation dynamics of the ethoxy radical in the two lowest electronic states, dissociative photodetachment experiments at 3.20 eV were carried out on the ethoxide anion, CH3CH2O(-), and its per-deuterated isotopologue. Production of excited radicals by photodetachment of the alkoxide anion was found to lead to only CH3 + H2CO products, with no indication of the energetically allowed H-loss channel, H + CH3CHO. Ab initio calculations for the anionic and neutral surfaces, including relevant isomerization and dissociation barriers, were carried out using the CBS-QB3 method to aid in interpretation of the data. The energetics observed in the photoelectron-photofragment coincidence spectra indicate that the calculated barrier (0.70 eV) for the process CH3CH2O → CH3 + H2CO and the stability of the CH3CH2O radical relative to those products are upper limits.
乙氧基自由基是燃烧化学中重要的物种；然而，关于其断裂途径存在相当大的争议。为了研究乙氧基自由基在两个最低电子态下的稳定性和离解动力学，在 3.20 eV 处对乙氧阴离子 CH3CH2O(-)及其全氘代同位素进行了离解光电子谱实验。光解烷氧阴离子产生的激发态自由基仅导致 CH3 + H2CO 产物，没有能量允许的 H 损失通道 H + CH3CHO 的迹象。使用 CBS-QB3 方法对阴离子和中性表面进行了从头算计算，包括相关的异构化和离解势垒，以帮助解释数据。光电子-光碎片符合能谱中观察到的能量学表明，计算出的 CH3CH2O → CH3 + H2CO 过程的势垒（0.70 eV）以及相对于这些产物的 CH3CH2O 自由基的稳定性是上限。
