The Microwave Absorption Spectrum of Acetone Vapor

Rotational and Torsional Properties of Various Monosubstituted Isotopologues of Acetone (CH3–CO–CH3) from Explicitly Correlated Ab Initio Methods

“…28 The isotopic substitution increases the gap between subcomponents. In the case of 13 C and 18 O isotopologues, the gap between splitting components is ∼0.15 cm −1 , whereas in the monodeuterated isotopologues, it was computed to be 15.0 cm −1 . This is the most unanticipated isotopic effect on the frequencies.…”

“…The computed values are parameters of the asymmetrically reduced Hamiltonian 52 (within the I r representation, and the a-axis was selected as the Z axis). For the main isotopologue and for the 13 C isotopologues, the computed values are compared with those of Groner et al 20,21 and for the monodeuterated species with those of Vacheran et al 18 Acetone has peculiar behavior that has not been observed in other similar species such as dimethyl ether, 53,54 because the internal rotation barrier is very low. The variation of electronic energy with the CH 3 torsion is small producing a very smooth potential energy surface.…”

“…Spectrum interpretation is challenging due to the large interactions between internal and overall rotation. In 1952, Weatherly and Williams 13 first observed four strong rotational transitions using microwave spectroscopy, but they were unsuccessful in assigning them. The microwave spectrum was first analyzed by Swalen and Costain 14 who assigned four transitions with J ≤ 2 determining the dipole moment and the internal rotation barrier.…”

“…ΔB vib represents the vibrational contribution to the rotational constants derived from the GVPT2 α ir vibration−rotation interaction parameters. 50 Experimental rotational constants are available for the main isotopologue as well as for the isotopologues containing 18 O, 13 C, and D, 18,20,21,27 although the majority of the recent previous studies focus on the main variety. The experimental data for the main isotopologue and the 13 C isotopologues have been derived by fitting the observed lines to an effective rotational Hamiltonian designed for molecules with two periodic large-amplitude motions, dimethyl ether, with similar properties to acetone.…”

Microwave spectra of mono-13C substituted acetone, (CH3)2CO

“…Acetone is among the earliest species studied by microwave spectroscopy with four lines observed, but not assigned, by Weatherly and Williams [1]. The first microwave structural study of acetone was reported by Swalen and Costain [2], who examined the normal species and the d 6 isotopic form and reported a partial structure.…”