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