The Microwave Spectra and r0, rs, and rm Structures of Ethylene Oxide

The rotational spectra of ten isotopic species of ethylene oxide, 12C2H416O, 12C13CH416O, 12C2H418O, 12C2H3D16O, cis- and trans-12C2H2D216O, 12C13CH2D216O, and 12C2H2D218O were observed. A least-squares fit including centrifugal distortion effect to the first order was made to derive the effective values of the A′, B′, C′, τ′aaaa, τ′bbbb, τ′cccc, and τ′aabb parameters and their correlation factors; τ′bbcc and τ′aacc were found to be insignificant. The rotational constants were used to determine the r0, rs, and rm structures. The structural parameters were derived as: & r_0(CC)=1.470±0.003, r_s(CC)=1.466±0.002, r_m(CC)=1.462±0.003, & r_0(CH)=1.085±0.004, r_s(CH)=1.085±0.001, r_m(CH)= 1.086±0.004, & r_0(CO)=1.434±0.002, r_s(CO)=1.431±0.001, r_m(CO)=1.428±0.002, & ∠_0HCH=116.28±0.69, ∠_SHGH=116.61±0.09, ∠_mHGH=116.92±0.69, θ0=22.34±0.46, θs=21.99±0.11, θm=21.63±0.48 in units of Å and degrees; θ represents the angle of the H2C plane to the CC bond. The indicated error limits are 2.5 times the variances.