Benz anthracene, spectrum

A second vital observation was made when Mayneord, a physicist, joined in the research effort and decided to examine the conspicuous fluorescence of the many carcinogenic distillates present in Kennaway s laboratory. He found that most of the carcinogenic tars exhibited a common fluorescence spectrum (X 400, 418 and 440 nm) but, in subsequent studies with Hieger, none of the hydrocarbons available at that time exhibited these spectral characteristics (7 ). The spectrum of benz[a]anthracene was found to be similar to, but of longer wavelength than, that of the carcinogenic preparations but this similarity directed Kennaway s attention to Clar s report of the synthesis of dibenz[a hjanthracene (10). Tumors were obtained when this hydrocarbon was repeatedly painted on to mice and thus it was established that the properties necessary to elicit tumors in animals were contained within the structure of a single pure chemical compound (11). 

Fig. 3.5. Fluorescence spectrum of benz[a]anthracene in n-heptane liquid solution at 300 K (top) and in n-heptane frozen solution at 15 l< (bottom). Concentration ...

In the case of benz[a]anthracene the positions 7 and 12 are approximately equivalent. Mackor and collaborators therefore discussed the effect of the position of methyl groups on the spectrum of the proton addition complex benz[a]anthracene in connection with the investigation of the basicity of methyl-benz[a]anthracenes (Mackor et al., 1956). The carbonium ions A and B are present in solution ... 

Figure 5. MI fluorescence spectrum of LC Fraction V from Synthoil at two excitation wavelengths. BaA = benz[a]anthracene C = chrysene U = unknown P = pyrene (artifact not present in fraction).

Another indication that resonance might increase planarity is seen in Figure 3. Absorbance spectra for three similar PAHs are shown. The top spectrum is of tetrabenzo[a,cdj,Zra]perylene (compound 25), which results from the condensation of 7H-benz[cfe]anthracen-7-one with itself. The bottom spectrum is of dibenzo[j fc,wi)]dinaphtho-2,l,8,7-de/g 2, l, 8, 7 -opgr]pentacene (compound 33), which results from 6H-benzo[cfe]pyren-6-one condensation. The middle spectrum is of an isomer resulting from the condensation of 7H-benz[cfe]anthracen-7-one with 6H-benzo[de]pyren-6-one (compound 2). Although the three spectra are remarkably similar in band... 

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