EXPERIMENTAL AND THEORETICAL-STUDIES OF THE UNIMOLECULAR DECOMPOSITION OF NITROSOBENZENE - HIGH-PRESSURE RATE CONSTANTS AND THE C-N BOND STRENGTH

The unimolecular decomposition of nitrosobenzene has been studied at 5 53-648 K with and without added NO under atmospheric pressure. Kinetic modeling of the measured C6H5NO decay rates by including the rapid re verse reaction and minor secondary processes yielded the high-pressure first-order rate constant for the decomposition C6H5NO-->C6H5+NO (1), k(1)(infinity)=(1.42+/-0.13) x 10(17) exp [-(55 060+/-1080)/RT] s(-1) , where the activation energy is given in units of cal/mol. With the t hermodynamics third-law method, employing the values of k(1)(infinity) and those of the reverse rate constant measured in our earlier study by the cavity ring-down technique between 298 and 500 K, we obtained t he C-N bond dissociation energy, D-0(o) (C6H5-NO)=54.2 kcal/mol. at 0 K, with an estimated error of +/-0.5 kcal/mol. This new, larger bond d issociation energy is fully consistent with the quantum mechanically p redicted value of 53.8-55.4 kcal/mol using a modified Gaussian-2 metho d. Our high-pressure rate constant was shown to be consistent with tho se reported recently by Horn et al. (ref 13) for both forward and reve rse reactions after proper correction for the pressure falloff effect.