Analysis Of The Rotational Structure In The High-resolution Ir Spectrum Of Trans-hexatriene-3-d1

For use in determining the semiexperimental structure of {\em trans}-hexatriene, its 3-{\em d}$_1$ isotopologue has been synthesized and the high-resolution (0.0015 cm$^{-1}$) IR spectrum has been recorded. The rotational structure in four C-type bands has been analyzed. These bands are for $\nu$$_{26}$ at 997.4, $\nu$$_{28}$ at 908.8, $\nu$$_{29}$ at 902.2, and $\nu$$_{32}$ at 678.6 cm$^{-1}$, which are all out-of-plane modes. Ground state rotational constants are {\em A}$_0$ = 0.7952226(8), {\em B}$_0$ = 0.0446149(7), and {\em C}$_0$ = 0.0422661(4) cm$^{-1}$. The inertial defect is –0.2009 amu {\AA}$^{2}$, which confirms planarity for this molecular species. The ultimate intent of this investigation is to evaluate the degree to which the “C=C” bonds are lengthened and the sp$^2$–sp$^2$ “C–C” bonds are shortened in comparison with localized bonds and with butadiene