Investigation of Demetallated Geoporphyrins: An Application of Friedel-Crafts Acetylation

It is well-known that β-(H) unsubstituted porphyrins present in sediments exclusively. Recently, several β-(H) unsubstituted porphyrins have been isolated by HPLC and identified by CI-MS and 'HNMR. However, many aspects of their characterisation remain unresolved. In the present papers, Friedel-Crafts acetylation, thin layer chromatography and Probe-MS are used for investigation of geoporphyrins in Lmk6. Ten red bands were obtained from TLC plate. The results show the methods could separated the porphyrin isomers roughly, and are able to reveal the characterisation of β-(H) unsubstituted porphyrins. For instance, A-4 series mainly occurs in β -(H) unsubstituted fraction and A-8 series only appears in fully alkylated fraction. Normally, β-(H) unsubstituted porphyrins are rich in the compounds of low carbon numbers. Results also show the TLC behaviour of Cu porphyrins. For fully alkylated porphyrins, R_f of A series that of A-2 and A-4 that of A-8. However, for β-(H) unsubstituted porphyrins. R_f ofAseries that of A-2 series.