13H-Dibenzo[a,g]fluoren-13-one

The crystal structure determination of 13H-dibenzo[a,g]fluoren-13-one, C₂₁H₁₂O, has shown the molecule to be distorted from planarity as a consequence of the repulsive interaction between an O_carbonyl lone pair and the juxtaposed proton. These results substantiate an earlier indication of this interaction, suggested by a conspicuously low field absorption in the ¹H NMR spectrum of this compound.