E-2 Some polycyclic components of tobacco smoke

FIGURE XVII.E-2 Some polycyclic components of tobacco smoke. 

Since nicotine is the most abundant and best known tobacco alkaloid, its pyrolysis has been thoroughly studied [Woodward et al. (4275a), Jarboe and Rosene (1923a)]. More recent work [Kaburaki et al. (2006)] on the pyrolysis of nicotine and various alkyl-pyridines has resulted in a proposed mechanism for the thermal degradation of nicotine. .. Schmeltz [Schmeltz et al. (3499)] also studied nicotine and identified a number of previously unreported compounds in the nicotine pyrolysates. .. These included pyrrole, acenaphthene, indole, skatole, and anthracene and/or phenanthrene. However, the presence of dibenzacridines and dibenzcarbazole, previously reported in nicotine and pyridine pyrolysates, could not be confirmed [Van Duuren et al. (4027)]. 

In ongoing studies we are now identifying those compounds that are formed from nicotine only as minor compounds ( 0.1%) which nevertheless can contribute to the toxicity of the smoke. To this group of minor smoke constituents having nicotine as a precursor belong the dibenzacridines [Van Duuren et al. (4027)]. .. 

Most pyrolysis studies with tobacco, tobacco extracts, extract fractions, individual components, and tobacco additives are performed in a nitrogen atmosphere. This procedure has often been criticized on the grounds that many of the toxic constituents formed during smoking of tobacco products occur as a result of combustion in air rather than in a nitrogen atmosphere. This criticism, however, cannot 

With regard to the production of dibenzacridines and the dibenzocarbazole from nicotine during pyrolysis and the smoking process. Table XVll.E-1 summarizes the current state of knowledge. 

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