A study of the conformational isomerism of n-propyl nitrate by microwave spectroscopy.

• Microwave spectra were recorded of the anti-anti and anti-gauche conformers of n -propyl nitrate. • Spectra of five isotopologues for each conformer have been assigned and fit. • The fit was made to a semi-rigid Hamiltonian including nuclear quadrupole hyperfine coupling. • r 0 and r s structural parameters have been determined from the data. The rotational spectrum of n -propyl nitrate was measured in the frequency range between 6 and 18 GHz using a Balle-Flygare Fourier transform microwave jet/cavity spectrometer. Parent, 13C and 15N isotopologue transitions for the lower-energy anti-gauche (AG) conformer were found using this instrument. The search for spectra from other conformers was performed using a broadband chirped-pulse jet spectrometer. Transitions from the anti-anti (AA) conformer were observed in this manner. Parent, 13C and 15N isotopologue transitions for the AA conformer were rescanned using the cavity instrument to improve resolution and the signal-to-noise ratio. Rotational, centrifugal distortion, and nuclear electric quadrupole coupling constants for all conformers/isotopologues were fit using Pickett's SPFIT program. The structure of n -propyl nitrate is discussed considering these results. [ABSTRACT FROM AUTHOR]