On the formation of the so-called arsanthrene

The structure of Kalb's “arsanthrene oxide” and “arsanthrene” have been reinvestigated. The “arsanth-rene oxide” is monomeric and is therefore properly termed 5,10-epoxy-5,10-dihydroarsanthrene( 6 ). A spectroscopic study of “arsanthrene” revealed that this compound has the dimeric structure 12 corresponding to the photodimer of anthracene. Mechanisms of formation of dimeric “arsanthrene” and the possible dissociation of dimeric “arsanthrene” into its monomer by reaction with a dienophile at elevated temperature are discussed. An attempt to synthesize arsanthrene ( 7 ) by dehalogenation of 5,10-dichloro-5,10-dihydroarsanthrene ( 5 ) was unsuccessful. The mass spectral fragmentation patterns of some 5,10-dihydroarsanthrenes are recorded.