A 3-ethyl-4-methylpyrrole unit in etioporphyrin was shown to be converted to a 3, 4- dimethylpyrrole unit by the action of heat, which was proved to be catalyzed by Na- montmorillonite. Time courses of the reaction could be followed by analyzing 2-ethyl-3- methyl-and 2, 3-dimethylmaleimide after chromic acid oxidation of the porphyrin. The ratio of these maleimides was proposed as a new maturity indicator for sedimentary organic ...
