ANALYSIS OF THE ROTATIONAL STRUCTURE IN A C-TYPE BAND IN THE HIGH-RESOLUTION INFRARED SPECTRUM OF $trans,trans$-1,4-DIFLUOROBUTADIENE-1-$d_{1}$

Author Institution: Department of Chemistry; and Biochemistry, Oberlin College, Oberlin, OH 44074; Physikalish-Chemisches Institut der Justus Liebig; Universitat, Heinrich-Buff Ring 58, D-35392, Giessen, GermanyA mixture of deuterium isotopomers of {\em trans,trans}-1,4-difluorobutadiene (ttDFBD) was prepared by partial exchange with NaOD/D$_{2}$O. A prominent component of the mixture was the 1-{\em d}$_{1}$ species. The rotational structure in a C-type band of this species centered at 920.5 cm$^{-1}$ was analyzed in the high-resolution (0.002 cm$^{-1}$) infrared spectrum. The analysis of this band was compromised by large contributions from a C-type band at 893 cm$^{-1}$ in the spectrum of ttDFBD-1,4-{\em d}$_{2}$. Provisional ground state rotational constants for ttDFBD-1-{\em d}$_{1}$ are reported. We have recently shown that 1-fluoroethylene can be exchanged with NaOD/D$_{2}$O to give 1-fluoroethylene-1-{\em d}$_{1}$, which can be used in known chemistry to make pure DFBD-1-{\em d}$_{1}$. An improved high-resolution infrared spectrum of ttDFBD-1-{\em d}$_{1}$ will be obtained. This method will also yield {\em cis,cis}-DFBD-1-{\em d}$_{1}$ for investigation. Rotational constants for ttDFBD-1-{\em d}$_{1}$ and ccDFBD-1-{\em d}$_{1}$ are needed for determining the semi-experimental equilibrium structures of the two nonpolar isomers of DFBD