40 Discussion 



(ii) energetically one would expect the symmetrical structure to be favoured 



because of its greater conjugation; and 

 (iii) Wang's postulatedfstructure would imply that porphyrin basicity should be 



comparable to pyrrole itself whereas in fact it is many p^ units stronger. 



In our experience the reaction between anhydrous ferric chloride and dimethyl- 

 protoporphyrin ester led either to the mono- or di-cationic species, probably due to 

 the difficulty of removing the last trace of water from the system. It would be inter- 

 esting to have the infra-red spectrum of the dihydrochloride for comparison with the 

 other species. 



