Obenchain Daniel A, Hartwig Beppo, Frohman Daniel J, Grubbs G S, Long B E, Pringle Wallace C, Novick Stewart E, Cooke S A
Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany.
Department of Chemistry, Wesleyan University, 52 Lawn Avenue, Middletown, CT 06459, USA.
Molecules. 2025 May 5;30(9):2051. doi: 10.3390/molecules30092051.
Rotational spectra for hexafluoroacetone imine, the singly substituted C isotopologues, and the N isotopologue, have been recorded using both cavity and chirped pulse Fourier transform microwave spectrometers. The spectra observed present as being doubled with separations between each pair of transitions being on the order of a few tens of kilohertz which is consistent with a large amplitude motion producing two torsional substates. The observed splitting is most likely due to the combined motions of the CF3 groups, for which the calculated barrier is small. However, no transitions between states could be observed and, similarly, no Coriolis coupling parameters were required to achieve a satisfactory fit for the transition frequencies. Hence, and somewhat curiously, the two states have been fit independently of each other such that the two states may simply be considered near-equivalent conformers. The structural properties of hexafluoroacetone imine are compared with two isoelectronic molecules hexafluoroisobutene and hexafluoroacetone. Rotational constants, quartic centrifugal distortion constants, and the N nuclear electric quadrupole coupling tensor have been determined and are presented together with supporting quantum chemical calculations.
已使用腔式和啁啾脉冲傅里叶变换微波光谱仪记录了六氟丙酮亚胺、单取代碳同位素异构体以及氮同位素异构体的转动光谱。观察到的光谱呈现为双线，每对跃迁之间的间隔约为几十千赫兹，这与产生两个扭转亚态的大幅度运动一致。观察到的分裂很可能是由于CF3基团的组合运动导致的，其计算出的势垒较小。然而，未观察到态之间的跃迁，同样，也不需要科里奥利耦合参数来实现对跃迁频率的满意拟合。因此，有点奇怪的是，这两个态是相互独立拟合的，以至于这两个态可以简单地被视为近等价构象体。将六氟丙酮亚胺的结构性质与两个等电子分子六氟异丁烯和六氟丙酮进行了比较。已确定了转动常数、四次离心畸变常数以及氮核电四极耦合张量，并与支持性的量子化学计算结果一同给出。
