DECARBOXYLATION OF CRYSTALLINE 2-CARBOXY-3-HYDROXYDIBENZO [A,C]TROPONE FOLLOWED BY SOLID-STATE CRYSTALLIZATION

Thermal decarboxylation of 2-carboxy-3-hydroxydibenzo[a,c]tropone (1) in a crystalline environment produces 3-hydroxy-dibenzo[a,c]tropone (2 ) accompanied by disordering of the crystalline lattice. Spectroscopic data on the decarboxylated solid suggest that 2 does not form intermo lecular hydrogen bonds under the influence of the structure of the mot her crystal of 1. Upon annealing, crystallization of 2 takes place and the crystal structure eventually becomes identical to that of the cry stal obtained by recrystallization from ethanol. The process of crysta llization of 2 is discussed in terms of the crystal structures of both the starting compound 1 and the decarboxylated product 2.