Pure rotational transitions of methyl vinyl ketone oxide, or the so called methyl-vinyl Criegee intermediate, were observed by Fourier-transform microwave spectroscopy. Among the four possible conformers of this species, predicted by theory within an energy window of 3 kcal/mol, only the lowest-energy conformer, the syn-trans form, was detected in a discharged jet of a 1,3-diiode-but-2-ene (either in Z- or E-conformation) and O₂ mixture diluted in Ar. Thirty pure rotational transitions with internal rotation splitting of the methyl top were observed. The observed frequencies were analyzed by the XIAM program, yielding an internal rotation barrier of 702.8(28) cm^–1, which reasonably agrees with a theoretical value of 680 cm^–1 determined with CCSD(T)/cc-pVTZ.

中文翻译：

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用不饱和烃取代基检测Criegee中间体：甲基乙烯基酮氧化物的傅里叶变换微波光谱法。

通过傅立叶变换微波光谱法观察到甲基乙烯基酮氧化物或所谓的甲基乙烯基Criegee中间体的纯旋转转变。间这一物种的四种可能的构象异构体，预测受理论的3能量窗内千卡/摩尔，仅最低能量构象，则顺式-反式形式，在的放电喷射检测到1,3- diiode-但-2-烯（Z或E构型）和O ₂混合物稀释在Ar中。观察到三十个纯旋转转变，其中甲基顶部内部旋转分裂。通过XIAM程序分析了观察到的频率，得出内部旋转屏障为702.8（28）cm ^–1，这与以CCSD（T）/ cc-pVTZ确定的理论值680 cm ^–1合理地吻合。