The Raman and infra-red spectra of carbon suboxide

Abstract

The infra-red and Raman spectra of carbon suboxide have been redetermined since earlier data did not permit an unequivocal decision as to the molecular symmetry. The infra-red spectrum of the gas was measured over the range 275 to 4600 cm$^{-1}$ using a Perkin-Elmer spectrometer. The Raman spectrum of the liquid (at -90 degrees C) was investigated using a photo-electric recording spectrometer constructed in this laboratory. No trouble was experienced with decomposition of the sample. The purity of the suboxide which was prepared from malonic acid was carefully checked by following changes in the infra-red and mass spectra at various stages of the purification. In this way several bands previously attributed to the suboxide were shown to be due to impurities. Details of a normal co-ordinate treatment are given, and with its aid all the observed bands are given satisfactory assignments on the basis of a linear molecule, symmetry D$_{\infty h}$. This necessitates the postulation of one infra-red active fundamental at about 198 cm$^{-1}$. Though this lies outside the region investigated here it has recently been observed by O'Loane in the course of investigations on a series of compounds in the far infra-red.