Pyrroles and related compounds. X.

Abstract The molecular ion nearly always produces the strongest peak in mass spectra of porphyrins. The macrocyclic nucleus is remarkably stable and fragmentation gives mainly “benzylic” ions. In derivatives of porphin this involves cleavage at the bond once removed from the macrocycle, but in chlorins the entire substituent is lost from the reduced “pyrrole” ring. Methyl esters of chlorins derived from chlorophyll lose directly 147 and 159 mass units in complex processes marked by strong metastable peaks. All the spectra contain a prominent series of peaks from doubly charged ions; a novel feature is loss of ketene from propionate side-chains.