15min:

NORMAN C. CRAIG, CATHERINE M. OERTEL AND DAVID C. OERTEL, Department of Chemistry, Oberlin College, Oberlin, OH 44074; MICHAEL J. TUBERGEN AND RICHARD J. LAVRICH, Department of Chemistry, Kent State University, Kent, OH 44242.; ANNE M. CHAKA, The Lubrizol Corporation, Wickliffe, OH 44092-2298.

Microwave spectra have been observed for cis,trans -1,4-difluorobutadiene, for the four ¹³C isotopomers in natural abundance, and for five deuterium isotopomers in a mixture prepared by partial exchange in NaOD/D₂O. Watson-type Hamiltonians have been fitted to the a-type and b-type transitions observed for each species. For the normal species, which is a near prolate top, A = 12988.3327(11), B = 1467.8791(3), and C = 1318.5845(3) MHz. From Stark effect measurements, the dipole moment components are µ_a = 0.660(4) D and µ_b = 2.213(5) D. A Kraitchman substitution analysis succeeds for the carbon atom backbone and for the hydrogen atoms on the end carbon atoms but does not for the interior hydrogen atoms. Most notably, I _b' for the 2-d₁ species is smaller than I _b for the normal species. To obtain a complete structure, results of DFT calculations with the adiabatic connection method were used for the bond lengths and bond angles of the interior C-H bonds. Otherwise the agreement of experiment and theory is good.