JET-COOLED ROTATIONAL SPECTRA AND AB-INITIO INVESTIGATIONS OF THE TETRAHYDROPYRAN - WATER-SYSTEM

The tetrahydropyran - water system was investigated by molecular-beam Fourier-transform microwave and free-jet millimeter-wave spectroscopie s and by ab initio calculations. The spectra of the C-13 isotopomers i n natural abundance of tetrahydropyran and of the 1:1 complex between tetrahydropyran and three isotopomers of water (H2O, D2O, and (H2O)-O- 18) have been assigned. A partial r(s) structure of the tetrahydropyra n monomer has been derived. In the complex, the water molecule lies in the plane of symmetry of tetrahydropyran; the water hydrogen involved in the hydrogen bond is axial with respect to the ring, while the fre e hydrogen is entgegen to the ring. The three atoms involved in the hy drogen bond adopt a slightly bent arrangement with an O-ring ... H dis tance of about 1.91 Angstrom and not less than (O-ring ... H-O) approx imate to 176 degrees. Additionally, ab initio calculations for the com plex were performed and found to be in agreement with the experimental results.