Abstract
Benzoporphyrins have been found as minor components of sedimentary porphyrins. It was proposed that benzoporphyrins were derived from bacteriochlorophylls c and d, which possess 3-methyl-4-n-propyl-, or 3-methyl-4-iso-butylpyrrole units. We established the diagenetic formation process of benzoporphyrins from these bacteriochlorophylls by heating experiments of model porphyrins (2,7,12,17-tetramethyl-3,8,13,18-tetra-n-propylporphyrin and 3,8,13,18-tetra-isobutyl-2, 7, 12, 17-tetramethylporphyrin). The heating products were oxidized by chromic acid to give phthalimides, in which the profile of phthalimides clearly indicates the formation of benzopyrrole units during heating experiments. These results imply that bacteriochlorophylls c and d are potential sources of benzoporphyrins found in petroleum and sedimentary rocks.
