Experimental observation of molecular-weight growth by the reactions of -benzyne with benzyl radicals.

The chemistry of -benzyne (-CH) is of fundamental importance due to its role as an essential molecular building block in molecular-weight growth reactions. Here, we report on an experimental investigation of the reaction of -CH with benzyl (CH) radicals in a well-controlled flash pyrolysis experiment using a resistively heated SiC microtubular reactor at temperatures of 800-1600 K and pressures near 30  torr. To this end, the reactants -CH and CH were pyrolytically generated from 1,2-diiodobenzene and benzyl bromide, respectively. Using molecular-beam time-of-flight mass spectrometry, we found that -CH associates with the benzyl to form CH radicals, which decompose at higher temperatures H-loss to form closed-shell CH molecules. Our experimental results agree with earlier theoretical calculations by Matsugi and Miyoshi [, 2012, , 9722-9728], who predicted the formation of fluorene (CH) + H to be the dominant reaction channel. At temperatures above 1400 K, we also observed the formation of CH radicals, most likely the resonance-stabilized fluorenyl π-radical. Our study confirms that molecular-mass growth the -CH + CH reaction provides a versatile pathway for introducing five-membered rings, and hence curved structures, into polycyclic aromatic hydrocarbons.