Knowledge Bank

The Raman spectra of gaseous and liquid cyclopropane were photographed with a reciprocal linear dispersion of $10.5cm-1$ per mm. The resolved rotational spectrum of the gas gave $Bo=0.6697\pm 0.0005$ $cm-1$. Although no rotational structure in the vibrational bands was resolved, the spectrum of the gas clarifies the vibrational assignments. The spectrum of the liquid, because of hindered rotation and consequent overlapping of bands, has led to incomplete frequency assignments. Nine of the ten Raman active fundamentals were recorded; of particular interest are $\nu 1=3038.0,\nu 8=3019.9$, and $\nu 13=1188.0$ $cm-1$. An infrared band centered at $3024cm-1$ has been previously assigned to $\nu 8$; it is suggested that this band should be classified as $2\nu 10+\nu 5$. The inactive frequency $\nu 4$ was assigned to a faint line at $1132.5cm-1$. The $\zeta$ constants of some of the degenerate vibrations were determined from the intensity contours of the bands.