Microwave determination of the structure of the C_s conformation of dipropyl ether

Microwave spectroscopyof dipropyl ether has been performed by supersonic jet molecular beam electric resonance spectroscopy and by molecular beam pulsed-jet Fourier transform spectroscopy. Calculations suggest that there are four distinct conformations of dipropyl ether that have energies within 0.5 kcal/mol of each other and have geometries of C_2ν, C₂, C_s, and C₁ symmetry. The geometry of the Cs conformation has been determined. The rotational constants of this conformation are A = 4793.6393(5) MHz, B = 1242.5098(3) MHz, C = 1053.3520(2) MHz, δ_J = 0.117(6) kHz, δ_K = 1.25(5) kHz, Δ_JK = -2.807(7) kHz, Δ_J = 0.448(2) kHz, and Δ_K = 11.57(3) kHz. The outer torsion angles (the O-C-C-C angles) are approximately 65°. Unassigned transitions in the microwave spectrum suggest that more than one additional conformation is present in both CW and pulsed molecular jets.