Exploring low barrier quantum tunneling and structural planarity in 3-methylstyrene conformers: Insights from microwave spectroscopy.

The first ground-state rotational spectrum of 3-methylstyrene (3MS) was measured by Fourier transform microwave spectroscopy under supersonic jet-cooled conditions. Transitions were assigned for two conformers: cis-3MS and trans-3MS. In the cis conformer, the vinyl group is oriented toward the methyl group, while in the trans conformer, it is positioned away from the methyl.

Identification of Two Stable Side-Chain Orientations of Valine Methyl Ester by Microwave Spectroscopy.

The rotational spectra of two valine methyl ester (ValOMe) conformers have been measured using a cavity-based Fourier-transform microwave spectrometer in the range of 9-18 GHz. Ten conformers of ValOMe were modeled using the ωB97XD/6-311++G(d,p) level of theory, and separate spectra arising from two lowest-energy conformations were observed and assigned. 44 rotational transitions were assigned to conformer I, the lowest-energy configuration, and were fit to Watson's -reduced Hamiltonian: = 2552.

Theoretical and Microwave Spectroscopic Characterization of Cyclobutenone: Planar or Puckered?

Cyclobutenone was characterized by high-resolution Fourier transform microwave spectroscopy for the first time. High-level, first-principles quantum chemical calculations at the B3LYP, CISD, MP2, and CCSD levels of theory were implemented to better understand the molecular structure and obtain model rotational and centrifugal distortion constants to aid in spectral assignment, and the results at the different levels of theory are compared. The assignment of the experimental spectrum provided fits of 2.

Probing the Electronic Environment of Methylindoles using Internal Rotation and (14)N Nuclear Quadrupole Coupling.

High-resolution rotational spectra were recorded in the 10.5-21.0 GHz frequency range for seven singly methylated indoles.