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Infrared characterization of formation and resonance stabilization of the Criegee intermediate methyl vinyl ketone oxide
Communications Chemistry ( IF 5.9 ) Pub Date : 2021-01-22 , DOI: 10.1038/s42004-020-00447-1
Chen-An Chung , Yuan-Pern Lee

Methyl vinyl ketone oxide (MVKO) is an important Criegee intermediate in the ozonolysis of isoprene. MVKO is resonance stabilized by its allyl moiety, but no spectral characterization of this stabilization was reported to date. In this study, we photolyzed a mixture of 1,3-diiodo-but-2-ene and O2 to produce MVKO and characterized the syn-trans-MVKO, and tentatively syn-cis-MVKO, with transient infrared spectra recorded using a step-scan Fourier-transform spectrometer. The O‒O stretching band at 948 cm−1 of syn-trans-MVKO is much greater than the corresponding bands of syn-CH3CHOO and (CH3)2COO Criegee intermediates at 871 and 887 cm−1, respectively, confirming a stronger O‒O bond due to resonance stabilization. We observed also iodoalkenyl radical C2H3C(CH3)I upon photolysis of the precursor to confirm the fission of the terminal allylic C‒I bond rather than the central vinylic C‒I bond of the precursor upon photolysis. At high pressure, the adduct C2H3C(CH3)IOO was also observed. The reaction mechanism is characterized.



中文翻译:

Criegee 中间体甲基乙烯基酮氧化物的形成和共振稳定的红外表征

甲基乙烯基酮氧化物 (MVKO) 是异戊二烯臭氧分解中的重要 Criegee 中间体。MVKO 由其烯丙基部分共振稳定,但迄今为止没有报道这种稳定性的光谱表征。在这项研究中,我们光解了 1,3-二碘-丁-2-烯和 O 2的混合物以产生 MVKO 并表征了-反式-MVKO 和暂定的-顺式-MVKO,使用瞬态红外光谱记录步进扫描傅里叶变换光谱仪。syn - trans -MVKO 在 948 cm -1处的 O-O 伸缩带远大于syn -CH 3的相应带CHOO 和 (CH 3 ) 2 COO Criegee 中间体分别位于 871 和 887 cm -1处,证实了由于共振稳定而产生更强的 O-O 键。我们还观察到碘代烯基自由基 C 2 H 3 C(CH 3 )I 在前体光解时发生裂变,以证实在光解时裂变的是末端烯丙基 C-I 键,而不是前体的中心乙烯基 C-I 键。在高压下,还观察到加合物 C 2 H 3 C(CH 3 )IOO。表征了反应机理。

更新日期:2021-01-22
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