Determination of the electron affinities of alpha- and beta-naphthyl radicals using the kinetic method with full entropy analysis. The C-H bond dissociation energies of naphthalene

The C-H bond dissociation energies for naphthalene were determined using a negative ion thermochemical cycle involving the gas-phase acidity (DeltaH(a cid)) and electron affinity (EA) for both the alpha- and beta -positions. T he gas-phase acidity of the naphthalene alpha- and beta -positions and the EAs of the alpha- and beta -naphthyl radicals were measured in the gas phas e in a flowing afterglow-triple quadrupole apparatus. A variation of the Co oks kinetic method was used to measure the EAs of the naphthyl radicals by collision-induced dissociation of the corresponding alpha- and beta -naphth ylsulfinate adducts formed by reactions in the now tube portion of the inst rument. Calibration references included both x and a radicals, and full ent ropy analysis was performed over a series of calibration curves measured at collision energies ranging from 3.5 to 8 eV (center-of-mass). The measured EAs are 33.0 +/- 1.4 and 31.4 +/- 1.0 kcal mol(-1) (1 kcal = 4.184 kJ) for the alpha- and beta -naphthyl radicals, respectively. The gas-phase acidit ies for naphthalene were measured by the DePuy silane cleavage method, whic h utilizes the relative abundances of aryldimethylsiloxides and trimethylsi loxide that result from competitive cleavages from a proposed pentacoordina te hydroxysiliconate intermediate. The measured acidities are 394.0 +/- 5.0 and 397.6 +/- 4.8 kcal mol(-1) for the alpha- and beta -positions, respect ively. The C-H bond dissociation energies calculated from the thermochemica l cycle are 113.4 +/- 5.2 and 115.4 +/- 4.9 kcal mol(-1) for the alpha- and beta -positions, respectively. These energies are, to within experimental error, indistinguishable and are approximately the same as the first bond d issociation energy for benzene. Copyright (C) 2001 John Wiley & Sons, Ltd.