Electronic theories carcinogenesis

Ozonation of benzo[r,s,t]pentaphene (7) followed by oxidative workup led to benzo[r,s,t]pentaphene-5,8-dione (12) (14%), phthalic acid (13) (4%), p-terphenyl-2,2, 3, 2"-tetra-carboxylic acid-2, 3 -anhydride (14) (10%), and 2-(o-car-boxyphenyl)- ,10-phenanthrenedicarboxylic acid anhydride (15) (3%), with a 56% recovery of unreacted 7, Ozonation of pentaphene (11) led to a peroxidic mixture which on oxidative workup led to 2,2 -binaphthyl-3,3 -dicarboxalde-hyde (16) (16%), 2,2 -binaphthyl-3,3 -dicarboxylic acid (17) (16%), and 13 (2%), with a 28% recovery of unreacted 11. A comparison of the reactivity to ozone of carcinogenic polycyclic aromatics benzo c]phenanthrene (1), 7,12-di-methylbenz [a] anthracene (2), 3-methylcholanthrene (3), dibenz[si,]] - (4), and dibenzlsi, ]anthracene (5), benzo Si -pyrene (6) and 7, and the noncarcinogen 11, all determined in our laboratory, leads us to conclude that there is no simple, consistent correlation between carcinogenicity, K-and L-region additivity towards ozone and the Pullmans electronic theory of carcinogenesis. 

The lesser carcinogens benzo[c]phenanthrene (l) (19) ( + ), di-benz[a,/]anthracene (4) (20) (+), and dibenz[a,h]anthracene (5 ) (24) (- — -) reacted with ozone predominantly at the K-region. Relative to 6, this response to ozone is the reversal of what would have been predicted by the electronic theory of carcinogenesis. 

Among the recent attempts to develop the theory of chemical carcinogenesis one encounters a number of speculations on the possible role in tumor formation of different factors which may be generally termed as physical or sterical. We have recently discussed in detail on a few occasions the theories involving the physical factors, among them the electron or excitation transfer mechanisms.27 32 26 24 In this communication, we should like to discuss, at least in part, some of the propositions concerning the role of steric effects in carcinogenesis by polycyclic aromatic hydrocarbons. 

The aim of this article is to review some of the literature from the past few years on the electronic and structural theories of chemical carcinogenesis by polycyclic aromatic hydrocarbons. The wealth of this literature means that a survey with any pretension to topicality must be selective. There are consequent dangers in a field notable also for spirited controversy (not always free from polemics). Such selection, although partly unconscious, is inevitably influenced by the viewpoint of the authors based on chemical experience, chiefly with solutions. In view of the emphasis on molecular geometry over a wider field of... 

Figure 4.4. Electronic transitions involved in theories of carcinogenesis...

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