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Weakly Bound Carbon−Carbon Bonds in Acenaphthene Derivatives and Hexaphenylethane

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journal contribution
posted on 21.01.2010 by Enoch Dames, Baptiste Sirjean, Hai Wang
A class of acenaphthene derivatives is shown to contain weak central carbon−carbon bonds that may be easily cleaved at high temperatures or even at ambient conditions to yield persistent free diradicals. To demonstrate the weak C−C bond strength, density functional theory calculations were carried out at several levels of theory for both the parent molecules and the diradicals resulting from the C−C bond cleavage. To assess the accuracy of the calculations, hexaphenylethane was chosen as a model compound due to its similarity with the molecules studied here, its great resonance stabilization, and long-standing history within the chemistry community. The C−C bond dissociation energy of hexaphenylethane was determined to be 11.3 ± 1.4 kcal/mol using a combination of isodesmic reactions and calculations at the M06-2X/6-31+G(d,p) level of theory. The types of molecules presented here are proposed as strong possibilities for the natural existence of free radicals in young and mature soot formed in hydrocarbon combustion.