15min:

NORMAN C. CRAIG, HANNAH A. FUSON, HENGFENG TIAN AND HERMAN VAN BESIEN, Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH 44074; ANDREW A. CONRAD AND MICHAEL J. TUBERGEN, Department of Chemistry, Kent State University, Kent, OH 44242.

Several deuterium isototopologues of cis -hexatriene have been synthesized in sub-millimole amounts. They include a mixture of the 1,1-d₂, cis -1-d₁, and trans -1-d₁ species and a sample of the 2-d₁ species. Microwave spectra for b -type transitions were observed in the 12-21 GHz range on the jet-beam, mini-cavity FT instrument at Kent State University. cis -Hexatriene has a small dipole moment of approximately 0.05 D. For the 1,1-d₂ species, 11 lines were found, and for each of the two 1-d₁ species, 9 lines were observed. For the 2-d₁ species, 10 lines were measured. Ground state rotational constants were fitted to the transitions using quartic centrifugal distortion constants computed with the B3LYP/cc-pVTZ model for each isotopologue. In prior work, rotational constants for the ¹³C species of cis -hexatriene were observed in natural abundance. Thus, we are close to having sufficient experimental information for determining a semiexperimental equilibrium structure for cis -hexatriene. The principal goal is to assess the effect of pi-electron delocalization on the C₆ backbone in comparison with butadiene.