1. Thomas A. Blake and Robert L. Sams
Rotational Analysis of Bands in the High-Resolution Infrared Spectra of trans,trans- and cis,cis-1,4-Butadiene-2-d1
Norman C. Craig, Deacon J. Nemchick, Clay C. Easterday, Ethan C. Glor, and Drew F. K. Williamson,
Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH 44074, USA
Thomas A. Blake and Robert L. Sams
Environmental Moleculat Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352

2. Overall Goal
Determine semi-experimental equilibrium structures for the isomers of 1,4-difluorobutadiene (DFBD).
Evaluate the influence of fluorine substitution on the CC bond lengths and bond angles in butadiene. (Strong influence of fluorine on C3 and C4 rings.)

3. Steps in Determining Semi-Experimental Equilibrium Structures
Obtain ground state rotational constants from high-resolution IR or MW spectra.
Do so for a full series of isotopomers.
Use quantum chemistry (triple zeta level) to compute vibration-rotation constants (alphas).
Find equilibrium rotational constants
Obtain an re structure from a global fit of all equilibrium rotational constants.

4. Synthesis Isotopomers of DFBD are made by modification of an assembly strategy.1
1H.-G.Viehe and E. Franchimont Chem. Ber. 1964, 97,

5. IR spectrum (0.1 cm-1 resol.) cis,cis-2-d1 species
A-type
C-type

6. C-type Band (0.0013 cm-1 resol.) of cis,cis-2-d1 Species

7. A-type Band (0.0013 cm-1 resol.) of cis,cis-2-d1 Species

8. Loomis-Wood Display for A-Type Band of cis-2-d1 Species
Ka 6lo yellow, 6hi magenta, 7 red, 8 green, 9 blue,
10 brown, 11 pink, 12 orange, 13 purple

10. IR spectrum (0.1 cm-1 resol.) trans,trans-2-d1 species
C-type

11. C-type Band (0.0013 cm-1 resol.) of trans,trans-2-d1 Species

12. C-type Band (0.0013 cm-1 resol.) of trans,trans-2-d1 Species

14. Conclusions
Analysis of the rotational structure in the high-resolution ( cm-1) infrared spectra of the cis,cis and trans,trans isomers of 1,4-difluorobutadiene has yielded ground state rotational constants.
Prior work gave ground state rotational constants for the normal species.1
The polar cis,trans isomer was investigated by MW spectroscopy.2
1. N. C. Craig, M. C. Moore, C. F. Neese, D. C. Oertel, L. Pedraza, T. Masiello J. Mol. Spectrosc. 2009, 254,
2. N. C. Craig, P. Groner, D. C. McKean, M. J. Tubergen Int. J. Quant. Chem. 2003, 95,

15. Support Dreyfus Foundation National Science Foundation Oberlin College
Washington State University