Knowledge Bank

All three CH-stretch vibrations of the methyl group in ethyl radical have been measured using high-resolution infrared spectroscopy in a slit supersonic discharge expansion source. Rotational assignment and analysis has been performed on each of these spectra providing rotational and centrifugal-distortion constants. We see one A-type band, which corresponds nominally to the symmetric stretch vibration, with a band origin at $2854.1027(3)cm-1$. Instead of a nominally degenerate vibration, the methyl asymmetric CH stretch is split into two B- and C-type bands with a separation of $124.5361cm-1$ due to internal rotation around the C-C bond. When compared to the splitting in $nitromethane,ab$ an analogous model system for hindered internal rotation, this separation is substantially larger.