The influence of structure factors on the thermooxidative destruction of linear and cyclic Di- and tetrapyrroles

The characteristics of the thermooxidative destruction of natural biladiene-a,c (bilirubin), dihydrobromides of several synthetic alkylated biladienes-a,c, 4,4'-dimethyl-3,3'-diethyl-5,5'-ethoxy-2,2'-dipyrrolylmethane, and 2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphin were studied by differential thermal analysis of solid samples. The influence of the molecular structure, including, the nature of peripheral substituents, macrocyclic effect, and salt formation on the thermal stability and special features of the thermal destruction of linear and cyclic di- and tetrapyrroles was analyzed. The enthalpies of vaporization of HBr from biladiene-a,c salts were calculated and their dependence on the proton affinity of the ligands in the gas phase considered.