Cai Jia-Rong, Su Jung-Hsuan, Lee Yuan-Pern
Department of Applied Chemistry and Institute of Molecular Science, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan.
Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan.
Commun Chem. 2022 Mar 4;5(1):26. doi: 10.1038/s42004-022-00644-0.
Methacrolein oxide (MACRO) is an important carbonyl oxide produced in ozonolysis of isoprene, the most abundantly-emitted non-methane hydrocarbon in the atmosphere. We employed a step-scan Fourier-transform infrared spectrometer to investigate the source reaction of MACRO in laboratories. Upon UV irradiation of precursor CHIC(CH)CHI (1), the CHC(CH)CHI radical (2) was detected, confirming the fission of the allylic C‒I bond rather than the vinylic C‒I bond. Upon UV irradiation of (1) and O near 21 Torr, anti-trans-MACRO (3a) was observed to have an intense OO-stretching band near 917 cm, much greater than those of syn-CHCHOO and (CH)COO, supporting a stronger O‒O bond in MACRO because of resonance stabilization. At increased pressure (86‒346 Torr), both reaction adducts CHC(CH)CHIOO (4) and (CHI)C(CH)CHOO (5) radicals were observed, indicating that O can add to either carbon of the delocalized propenyl radical moiety of (2). The yield of MACRO is significantly smaller than other carbonyl oxides.
甲基丙烯醛氧化物（MACRO）是异戊二烯臭氧分解过程中产生的一种重要的羰基氧化物，而异戊二烯是大气中排放最为丰富的非甲烷碳氢化合物。我们在实验室中使用步进扫描傅里叶变换红外光谱仪来研究MACRO的源反应。在前体CHIC(CH)CHI（1）受到紫外线照射时，检测到了CHC(CH)CHI自由基（2），这证实了烯丙基C‒I键而非乙烯基C‒I键发生了裂变。当（1）和O在接近21 Torr的压力下受到紫外线照射时，观察到反式-MACRO（3a）在917 cm附近有一个强烈的O‒O伸缩带，远大于顺式-CHCHOO和(CH)COO的该谱带，这表明由于共振稳定作用，MACRO中的O‒O键更强。在压力增加（86‒346 Torr）时，观察到了反应加合物CHC(CH)CHIOO（4）和(CHI)C(CH)CHOO（5）自由基，这表明O可以加成到（2）的离域丙烯基自由基部分的任何一个碳原子上。MACRO的产率明显低于其他羰基氧化物。
