Microwave Spectrum and Structure of Bicyclo[1.1.0]butane

The microwave spectra of four isotopic species of bicyclo[1.1.0] butane have been investigated and the rotational constants of each species have been determined. Combining these data with those of the previously studied normal isotopic species, a complete set of structural parameters have been found. These include C1–C3 = 1.497 Å, C3–C4 = 1.498 Å, C3–C6 = 1.071 Å, C–H (methylene) = 1.093 Å, ∠C1C3H6 = 128°22′, dihedral angle, α, between cyclopropane rings = 121°40′, ∠HCH = 115°34′. These results are discussed with regard to the electronic structure of the molecule.