Weakly bound carbon-carbon bonds in acenaphthene derivatives and hexaphenylethane.
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.
Dames
Enoch
E
Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California 90089-1453, USA.
Sirjean
Baptiste
B
Wang
Hai
H