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[Display omitted] • Microwave spectra were recorded of the anti- gauche -anti (AGA), AAA , GAA , GGA and AGG conformers of n -butyl nitrate. • Spectra of the parent isotopologues of the five conformers were assigned and fit. • Spectra of the 13C and 15N isotopologues of the AGA conformer were assigned and fit. • r 0 and r s structural parameters were determined for the AGA conformer from the experimental data. The microwave spectrum of n -butyl nitrate was recorded in the 5 to 20 GHz frequency range using broadband chirp and narrowband pulse excitation molecular jet Fourier transform microwave spectrometers. A quantum chemistry structural analysis yielded thirteen stable conformers. Among them, the five most energetically stable conformers were observed in the experimental spectra. The most stable conformer features a butyl chain with an anti - gauche - anti conformation (AGA) where the γ-carbon atom is about 64° out of the nitrate plane. For this conformer, spectra of all 13C and 15N minor isotopologues could be measured. The conformer with a straight butyl chain (AAA), and three other conformers (GAA , GGA , and AGG) were also observed. Accurate rotational constants, centrifugal distortion constants, and 14N nuclear quadrupole coupling constants could be deduced and compared to the theoretical values. [ABSTRACT FROM AUTHOR]

[Display omitted] • Questioning the planarity of the open shell difluorocyanomethyl radical. • Complex hyperfine structures observed in the microwave spectrum. • Spin-rotation coupling, nuclear quadrupole coupling, and Fermi contact interactions. The pure rotational spectrum of the open shell difluorocyanomethyl radical, ĊF 2 CN, has been measured using two Balle-Flygare-type cavity Fourier-Transform-Microwave (FTMW) spectrometers both equipped with pulsed discharge nozzles. A total of 156 transitions (from N = 1 – 0 to 6 – 5, and K a = 0, 1, 2, 3) in the electronic ground state were observed between 6.5 GHz and 38.4 GHz with a typical linewidth of ∼5 kHz full-width-half-maximum. A Hamiltonian that included semi-rigid rotor, spin-rotation, and nuclear hyperfine parameters was fit to the observed data set and these parameters have been interpreted and compared to similar radicals. Excellent agreement between experimental and uB3LYP/aug-cc-pVQZ calculated rotational constants, the experimental inertial defect, −0.6858(2) uÅ2, and the failure of a coupling scheme in which the fluorine nuclei are treated as identical and related by a C 2v symmetry axis combine to indicate a nonplanar structure for the ĊF 2 CN radical. [ABSTRACT FROM AUTHOR]