Knowledge Bank

Rotational spectra of cyclopenteneoxide and the argon cyclopenteneoxide van der Waals complex were studied using pulsed-jet Fabry-Perot Fourier transform microwave spectroscopy. Spectra of the normal isotopomer along with those of the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C singly substituted isotopomers for both the monomer and the complex were measured in the frequency region of 6-20 GHz. The boat structure for cyclopenteneoxide was confirmed with naturally abundant $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C isotopic substitution. For the argon cyclopenteneoxide complex, both \it a \rm and \it b\rm -type transitions were observed and the rotational constants for the all $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}$C isotopomer were determined to be A = 3268.2537(5), B = 993.3458(2), and C = 950.4300(2) MHz. The coordinates of the argon in the principal axis system of cyclopenteneoxide are \it a \rm = 0.27, \it b \rm = 0.42, and \it c \rm = 3.91 \AA, such that the argon atom is \it exo \rm to the bridged oxygen of the ring. An investigation into whether or not the argon atom undergoes large amplitude cross-ring motion will be presented.