Jet-cooled rotational spectra and structure of the cyclobutanone⋯hydrogen chloride complex

The rotational spectra of three isotopic species C4H6O⋯H35Cl, C4H6O⋯H37Cl and C4H6O⋯D35Cl of the hydrogen-bonded dimer formed by cyclobutanone and hydrogen chloride have been studied by means of microwave spectroscopy in a supersonic jet. Rotational constants, centrifugal distortion constants and Cl-nuclear quadrupole coupling parameters have been determined for the ground state and for a vibrationally excited state attributable to the ring-puckering motion of the cyclobutanone subunit. The spectroscopic constants have been interpreted in terms of a Cs symmetry in which the monomers are coplanar with: r(O⋯H)=1.88(3) Å, ∠(CO⋯H)=112.3(7)° and a deviation θ of the O⋯H–Cl nuclei from collinearity of 13.1(6)°.