Internal rotation in halogenated toluenes: Rotational spectrum of 2,5-difluorotoluene

Two Equivalent Internal Rotations in the Microwave Spectrum of 2,6‐Dimethylfluorobenzene

“…We will use the same notation for 26DMFB. The abbreviated symmetry labels (00), (01), (11), and (12) correspond to the A i (i = 1-4), G, E 3 and E 4 , and E 2 and E 3 , respectively, [42] given under the column S2 in Table 1 of Ref. [23].…”

“…If only the spin statistical weight is considered, the (01) torsional component is the strongest with the spin weight of 128, followed by the (00) species with 72 for K a K c = ee $ oo (e = even, o = odd) transitions and 56 for eo $ oe transitions. The spin weight of the (11)…”

“…5 05 could be assigned readily because their positions were predicted quite accurately. Symmetry considerations have shown that four torsion components (00), (01), (11), and (12) are expected due to the internal rotations of two equivalent methyl groups in 26DMFB. In the second step, a prediction taking into account these LAM effects was performed.…”

“…The assignments of the (01), (11), and (12) species lines were also checked with SFLAMS using the additional odd power term [Eq. (2)]…”

“…Especially for spectroscopy, the rotational spectrum of toluene has always attracted attention since its microwave spectrum was recorded and analyzed for the first time by Rudolph et al [1] Not only the structure of toluene was determined to great accuracy, several theoretical models and program codes have been also developed to reproduce the V 6 potential arising from the internal rotation of the C 3v methyl group attached to a phenyl frame with C 2v symmetry. [2][3][4][5] To gain insights into the substitution effect on this large amplitude motion (LAM) of toluene, studies on many fluorinated derivatives have been performed, such as the investigations on three isomers of fluorotoluene, [6][7][8] a systematic microwave investigation on the six isomers of difluorotoluene, [9][10][11][12][13] and the work on two isomers of trifluorotoluene. [14] All these studies have shown a variety of the potentials of the methyl torsion in both shape and height, which depend on the substituted position(s) of the fluorine atom(s).…”