Rotational Spectrum and Structure of Cyclohexene Oxide and the Argon–Cyclohexene Oxide van der Waals Complex

The rotational spectra of cyclohexene oxide and its van der Waals complex with argon have been observed with a Balle-Flygare type pulsed jet Fourier transform microwave spectrometer in the 6 to 20 GHz region. This work improves the existing rotational and quartic centrifugal distortion constants of cyclohexene oxide, its six singly substituted ¹³C, and the ¹⁸O isotopologue. In addition, the ¹⁷O isotopologue was observed in natural abundance. The quadrupole coupling constants for the ¹⁷O isotopologue are χ_aa = 8.855(5), χ_bb = −4.560(4), and χ_cc = −4.296(4) MHz. The argon–¹²C₆H₁₀¹⁶O complex has rotational constants of <i>A</i> = 2146.4825(2), <i>B</i> = 908.64292(8), and <i>C</i> = 859.00320(8) MHz. Additionally, the six unique singly substituted ¹³C isotopologues of the argon complex are reported here. The position of the argon that is consistent with the parent and six ¹³C complex rotational constants is above the ring on the side opposite the epoxide