Knowledge Bank

The infrared and Raman spectra of gaseous and solid $(CH3)2B(C2H3)$ and $(CH3)B(C2H3)2$ have been obtained over the frequency range 30 to $4000cm-1$. The Raman spectra of the liquids have also been recorded. Assignments of the normal modes have been made on the basis of band types, Raman depolarization values and characteristic group frequencies. The spectral data indicate that both molecules are planer allowing for the maximum overlap between the empty p orbital on the boron atom and the $\pi$ system of the vinyl group. A two fold periodic barrier of 4.2 kcal/mole was calculated from the band in the spectrum of the Raman gas at $100cm-1$ in dimethylvinylborane. These data are consistent with the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}H$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C$ low temperature NMR results. No torsional data were obtained on divinylmethylborane due to the complex low frequency spectral region.