The r(e) structure of cyclopropane

A long-standing controversy regarding the r(e),structure of cyclopropane is resolved by performing high-level quantum chemical calculations and analyz ing the experimental rotational constants for C3H6 and C3H4D2 augmented by calculated vibrational corrections. For the latter, a least-squares fit yie lds the following set of parameters: r(e) (CC) = 1.5030(10) Angstrom, rh(CH ) 1.0786(10) Angstrom, and alpha(e)(HCH) = 114,97(10)degrees, which compare favorably with both the pure computational result obtained at the CCSD(T)/ cc-pVQZ level as well as an earlier estimate of the r(e) structure of cyclo propane:based on analysis of gas-phase electron diffraction data. Our resul ts are in rather poor agreement with a structure based on a previous analys is of the rotational constants that used empirically estimated vibrational corrections.