Methyl group internal rotation and the choice of Hamiltonian for the rotational spectrum of 1,1-difluoroacetone
Methyl group internal rotation and the choice of Hamiltonian for the rotational spectrum of 1,1-difluoroacetone
复制标题
DOI：
10.1016/j.jms.2012.07.004
复制
发表时间：
2012-10
影响因子：
1.4
通讯作者：
G. Grubbs;P. Groner;S. Novick;S. Cooke
中科院分区：
文献类型：
--
作者：
G. Grubbs;P. Groner;S. Novick;S. Cooke
用7.5-16.5GHz波段的宽带转动光谱研究了丙酮分子的不对称性效应。使用主轴方法分析包含甲基内旋转信息的宽带光谱，随后使用（i）组合轴方法和（ii）其中哈密顿量具有以傅立叶级数表示的矩阵元素的方法分析。首次给出了甲基内旋转的光谱常数和有效能垒。结果进行了比较，相关的分子，其中它表明，羰基有效地限制了邻C（O）CH 3结构上的影响。所进行的光谱分析表明，除了A和Ir之外，在所有沃森约化和表示的组合中，哈密顿量都具有令人满意的收敛性。在这种组合中，比率（2A−B−C）/（B−C）很大，导致四次离心畸变常数δ K的值不合理地大，这反过来又阻止了令人满意的本征值解。
The effects of partial fluorination on acetone have been examined using broadband rotational spectroscopy within the 7.5–16.5GHz region. The broadband spectrum, which contains information on the methyl group internal rotation, was analyzed using a principal axis method, and subsequently analyzed using (i) a combined axis method and (ii) a method in which the Hamiltonian possesses matrix elements expressed as Fourier series. Spectroscopic constants and effective barriers to methyl group internal rotation are presented for the first time. Results are compared to related molecules where it is shown that the carbonyl group effectively limits the effects of fluorination on the adjacent C(O)CH3structure. The spectroscopic analyses performed demonstrate a satisfactory convergence of the Hamiltonian in all combinations of Watson reduction and representation with the exception of A and Ir. Within this combination the ratio (2A−B−C)/(B−C) is large resulting in unreasonably large values of the quartic centrifugal distortion constant δKwhich in turn prohibits a satisfactory eigenvalue solution.