Ethylene combustion products obtained over a range of conditions regularly show peaks with retention times and mass spectra expected for C 20 H 10 polycyclic aromatic hydrocarbons (PAH) when analyzed by gas chromatography/mass spectrometry (GC/MS). Analysis by high-performance liquid chromatography with spectrometric diode-array detection (HPLC/DAD) yields three distinct peaks over the C 20 PAH elution interval whose UV-vis spectra differ from those of known PAH. These results, highly characteristic of ethylene flames, strongly suggested the presence of at least three C 20 H 10 PAH. Recent progress in PAH synthesis permitted the comparison of chromatographic and spectrometric data for flame samples with those of authentic dicyclopentapyrenes: dicyclopenta[cd,fg]pyrene, dicyclopenta[cd,mn]pyrene, and dicyclopenta [cd,jk]pyrene. The comparative analysis established that the three C 20 H 10 PAH long observed in ethylene flames were indeed the three dicyclopentapyrene isomers. Additional analysis of samples from a range of flames showed that the dicyclopentapyrenes are present in fullerene-deficient flames, but are absent in fullerene-producing flames. The dicyclopentapyrenes are notable for being isomers of corannulene, a possible fullerene precursor also found in a range of flames. The significance of these findings in relation to the flame production of fullerenes is discussed.
In order to investigate new aspects of polycyclic aromatic hydrocarbon (PAH) growth and soot formation, we have synthesized special reference standards of cyclopenta-fused PAH (CP-PAH) and ethynyl-substituted PAH. We have identified several of these CP-PAH and ethynyl-PAH in benzene droplet combustion products, using high pressure liquid chromatography (HPLC) and ultraviolet-visible (UV) absorption spectroscopy. Although one CP-PAH identified in these products-acenaphthylene-has previously been identified as a product of a variety of combustion systems, we have identified six additional CP-PAH and two ethynyl-PAH which have never before been unequivocally identified as the products of benzene pyrolysis or combustion: spectra we have obtained from specially synthesized reference standards. We also present the UV absorption spectra of two additional ethynyl-PAH reference standards -3-ethynylfluoranthene and 1 -ethynylpyrene ~ which we have synthesized.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.