SYSTEMATIC NOMENCLATURES 



105 



2.2. Systematic Nomenclatures 



There is thus evident need for a concise chemical nomenclature. 

 Systematic nomenclatures have been suggested by Fischer (798,8,20) 

 and Siedel {2551,2557). The term "tetrapj'rrane" was introduced 

 for the fully hydrogenated system and the number of double bonds 

 indicated in the usual way by "ene," "diene," "triene." (Fischer 

 and Siedel, according to German usage, use these words without the 

 final "e.") 



At first Fischer used the numbering A, which was later {820) 

 replaced by B (Fig. 9). The latter has also been adopted by Siedel. 



^^n"^ c-^j^^ c^j^^ c-^n 



(A) 



12 3 4 5 6 7 



l'\ Ap/^K /^i/^ 4^r^ / 

 (B) 



Fig. 9. Numbering of atoms in bile pigments. 



The terms "bilan" and "bilin" were suggested by Siedel for the 

 fully hydrogenated tetrapyrrane and the aromatic system of tetra- 

 pyrrotrienes (biliverdins), respectively, which bear hydroxy 1 groups 

 in 1' and 8'. After what has been said above about the use of the 

 term "bilin," its application for one special class of bile pigments is 

 not to be recommended. It is also better to avoid "ms" in (B), 

 standing for "meso" and supposed here to refer to the central carbon 

 atom /3, not to the side chains. 



The full name of bilirubin, according to the earlier nomenclature 

 of Fischer would be l,10-di(hydr)oxy-2,4,7,9-tetramethyl-3,9-divinyl- 

 tetrapyrro-ll,18-diene-5,6-dipropionic acid. (The position of double 

 bonds is indicated by the lower number of the two doubly linked 

 carbon atoms.) In Siedel's nomenclature, the name of bilirubin 

 would be either l',8'-di(hydr)oxy-l,3,6,7-tetramethyl-2,8-divinyl- 



