Knowledge Bank

The Raman spectra of vapor-phase 9,10-Dihydroanthracene have been recorded at 280 deg C. The low-frequency region shows three bands at 223, 171 and $119cm-1$. These have been assigned respectively as the in-phase ring-flapping ($\nu 29$), the in-phase ring twisting ($\nu 36$) and $(\nu 36)-(\nu 49)$, a difference band between $(\nu 36)$ and the ring-puckering $(\nu 49)$. The difference band demonstrates that the molecule is puckered with $C2\nu$, symmetry. The Raman spectra of the melt (140 deg C) and the solid have also been recorded and compared to the vapor. Assignments were made and compared to predictions from molecular mechanics (MM3) calculations.