Knowledge Bank

The microwave spectrum of meso-bisoxirane has been recorded in the R-band, K-band, and X-band regions. Vibrational spectra of the gas, liquid, and solid phases indicate that the compound exists as a mixture of two conformations, but the more stable trans conformation ($C1$ symmetry) has no dipole moment. Therefore, the very weak microwave spectrum was assigned to the gauche conformer ($C1$ symmetry), and RF-MW double resonance was necessary to confirm some assignments. The following rotational constants (MHz) and dipole moment components (D) have been obtained: $A=9187.45\mu a=1.08B=2651.80\mu b=0.35C=2608.92\mu c=2.80$ A structure for meso-bisoxirane which is consistent with these data has been determined and will be discussed with regard to the structures and conformational stabilities of the related compounds d,l-bisoxirane and bicyclopropyl.