Porterfield Jessica P, Baraban Joshua H, Troy Tyler P, Ahmed Musahid, McCarthy Michael C, Morgan Kathleen M, Daily John W, Nguyen Thanh Lam, Stanton John F, Ellison G Barney
Chemical Sciences Division, Lawrence Berkeley National Laboratories , Berkeley, California 94720, United States.
Harvard-Smithsonian Center for Astrophysics , Cambridge, Massachusetts 02138, United States.
J Phys Chem A. 2016 Apr 14;120(14):2161-72. doi: 10.1021/acs.jpca.6b00652. Epub 2016 Mar 31.
Both glycolaldehyde and glyoxal were pyrolyzed in a set of flash-pyrolysis microreactors. The pyrolysis products resulting from CHO-CH2OH and HCO-CHO were detected and identified by vacuum ultraviolet (VUV) photoionization mass spectrometry. Complementary product identification was provided by argon matrix infrared absorption spectroscopy. Pyrolysis pressures in the microreactor were about 100 Torr, and contact times with the microreactors were roughly 100 μs. At 1200 K, the products of glycolaldehyde pyrolysis are H atoms, CO, CH2═O, CH2═C═O, and HCO-CHO. Thermal decomposition of HCO-CHO was studied with pulsed 118.2 nm photoionization mass spectrometry and matrix infrared absorption. Under these conditions, glyoxal undergoes pyrolysis to H atoms and CO. Tunable VUV photoionization mass spectrometry provides a lower bound for the ionization energy (IE)(CHO-CH2OH) ≥ 9.95 ± 0.05 eV. The gas-phase heat of formation of glycolaldehyde was established by a sequence of calorimetric experiments. The experimental result is ΔfH298(CHO-CH2OH) = -75.8 ± 1.3 kcal mol(-1). Fully ab initio, coupled cluster calculations predict ΔfH0(CHO-CH2OH) of -73.1 ± 0.5 kcal mol(-1) and ΔfH298(CHO-CH2OH) of -76.1 ± 0.5 kcal mol(-1). The coupled-cluster singles doubles and noniterative triples correction calculations also lead to a revision of the geometry of CHO-CH2OH. We find that the O-H bond length differs substantially from earlier experimental estimates, due to unusual zero-point contributions to the moments of inertia.
乙醇醛和乙二醛均在一组闪速热解微反应器中进行热解。通过真空紫外（VUV）光电离质谱对由CHO-CH₂OH和HCO-CHO产生的热解产物进行了检测和鉴定。通过氩气基质红外吸收光谱提供了互补的产物鉴定。微反应器中的热解压力约为100托，与微反应器的接触时间约为100微秒。在1200K时，乙醇醛热解的产物为H原子、CO、CH₂═O、CH₂═C═O和HCO-CHO。采用脉冲118.2nm光电离质谱和基质红外吸收对HCO-CHO的热分解进行了研究。在这些条件下，乙二醛热解为H原子和CO。可调谐VUV光电离质谱给出了电离能（IE）（CHO-CH₂OH）≥9.95±0.05eV的下限。通过一系列量热实验确定了乙醇醛的气相生成热。实验结果为ΔfH298（CHO-CH₂OH）=-75.8±1.3kcal mol⁻¹。完全从头算的耦合簇计算预测ΔfH0（CHO-CH₂OH）为-73.1±0.5kcal mol⁻¹，ΔfH298（CHO-CH₂OH）为-76.1±0.5kcal mol⁻¹。耦合簇单双激发及非迭代三激发校正计算也导致了CHO-CH₂OH几何结构的修正。我们发现，由于对转动惯量的异常零点贡献，O-H键长与早期实验估计值有很大差异。
