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O2-Oxidation of Cyanomethylene Radical: Infrared Identi cation of Criegee Intermediates syn- and anti-NCC(H)OO
Bo Lu,Yuan-yuan Qin,Chao Song,Wei-yu Qian,Li-na Wang,Xiao-qing Zeng*
1.College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China;2.Department of Chemistry, Fudan University, Shanghai 200433, China
Abstract:
Cyanomethylene radical (HCCN) is an important intermediate in the nitrile chemistry in both the earth’s and the Titan’s atmosphere. Despite that the mechanism for the oxidation of HCCN has been already computationally explored, the key Criegee intermediate, NCC(H)OO, remains unobserved yet. By photolyzing mixtures (1:50:1000) of either HC(N2)CN/O2/N2 (266 nm) or HCCNCO/O2/N2 (193 nm) at 15.0 K, the elusive carbonyl oxides NCC(H)OO, in syn- and anti-conformations, have been generated and characterized with IR spectroscopy. The spectroscopic identification is supported by 18O-labeling experiments and the quantum chemical calculations at the BP86/6-311++G(3df,3pd) level. Upon subsequent UV-light irradiation, both conformers of NCC(H)OO further react with O2 and yield NCC(O)H and O3, whereas, the dioxirane isomer HC(O2)CN, which is lower than syn-NCC(H)OO by 23.7 kcal/mol at the CCSD(T)-F12a/aug-cc-pVTZ//BP86/6-311++G(3df,3pd) level, was not observed experimentally.
Key words:  Methylene radicals, Criegee intermediates, Oxidation, Photochemistry, IR spectroscope
FundProject:
附件
氰基取代亚甲基自由基的氧气氧化: 新颖Criegee中间体NCC(H)OO顺、反异构体的红外光谱探测
卢 博1, 秦园园1, 宋 超1, 钱伟煜1, 王丽娜2, 曾小庆*1,3
1.苏州大学材料与化学化工学部,苏州 215123;2.复旦大学化学系,上海 200433;3.b. 复旦大学化学系,上海 200433
摘要:
本文采用基质隔离红外光谱分别对15.0 K温度下的HC(N2)CN/O2/N2和HCCNCO/O2/N2混合物(1/50/1000)的激光光解过程开展了实验研究. 结果表明:两者在紫外激光光照下均可产生Criegee中间体NCC(H)OO的顺、反两种构象异构体. 对NCC(H)OO的红外光谱解析得到了氧同位素(18O)标记实验和BP86/6-311++G(3df,3pd)理论计算结果的支持. 实验发现NCC(H)OO在紫外光照下可进一步与氧气分子发生二次反应,生成氰基甲醛和臭氧,而未得到被理论所预测的能量较低的双环氧乙烷异构体cyclic-NCC(O2)H.
关键词:  亚甲基自由基,Criegee中间体,氧化,光化学,红外光谱
DOI:10.1063/1674-0068/cjcp2001004
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